├── .github └── workflows │ └── ci.yml ├── .gitignore ├── COPYING.md ├── README.md ├── README.org ├── default.nix ├── doc ├── links.org ├── nix.mac.org ├── nix.md ├── nix.org └── nix.org.el ├── nix ├── ci.nix ├── default.nix ├── direnv-nix-lorelei.nix ├── env_name_cleanup.patch ├── external │ ├── default.nix │ ├── sources.json │ └── sources.nix ├── home.nix ├── remove_trace.patch └── test │ ├── shell.nix │ ├── test.bats │ └── test.nix └── support ├── dependencies-upgrade ├── docs-generate └── tests-run /.github/workflows/ci.yml: -------------------------------------------------------------------------------- 1 | name: "CI" 2 | on: 3 | push: 4 | pull_request: 5 | jobs: 6 | build: 7 | strategy: 8 | matrix: 9 | os: [ubuntu-latest, macos-latest] 10 | name: ${{ matrix.os }} build 11 | runs-on: ${{ matrix.os }} 12 | steps: 13 | - uses: actions/checkout@v2 14 | - uses: cachix/install-nix-action@v14 15 | - uses: cachix/cachix-action@v10 16 | with: 17 | name: shajra 18 | signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}' 19 | - run: cat ~/.config/nix/nix.conf 20 | - run: nix --print-build-logs build --file nix/ci.nix 21 | - run: nix path-info --file nix/ci.nix 22 | - run: support/tests-run 23 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | result* 2 | home-fake/ 3 | nix-profile* 4 | -------------------------------------------------------------------------------- /COPYING.md: -------------------------------------------------------------------------------- 1 | ### GNU GENERAL PUBLIC LICENSE 2 | 3 | Version 3, 29 June 2007 4 | 5 | Copyright (C) 2007 Free Software Foundation, Inc. 6 | 7 | 8 | Everyone is permitted to copy and distribute verbatim copies of this 9 | license document, but changing it is not allowed. 10 | 11 | ### Preamble 12 | 13 | The GNU General Public License is a free, copyleft license for 14 | software and other kinds of works. 15 | 16 | The licenses for most software and other practical works are designed 17 | to take away your freedom to share and change the works. By contrast, 18 | the GNU General Public License is intended to guarantee your freedom 19 | to share and change all versions of a program--to make sure it remains 20 | free software for all its users. We, the Free Software Foundation, use 21 | the GNU General Public License for most of our software; it applies 22 | also to any other work released this way by its authors. You can apply 23 | it to your programs, too. 24 | 25 | When we speak of free software, we are referring to freedom, not 26 | price. Our General Public Licenses are designed to make sure that you 27 | have the freedom to distribute copies of free software (and charge for 28 | them if you wish), that you receive source code or can get it if you 29 | want it, that you can change the software or use pieces of it in new 30 | free programs, and that you know you can do these things. 31 | 32 | To protect your rights, we need to prevent others from denying you 33 | these rights or asking you to surrender the rights. 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The output from running a 165 | covered work is covered by this License only if the output, given its 166 | content, constitutes a covered work. This License acknowledges your 167 | rights of fair use or other equivalent, as provided by copyright law. 168 | 169 | You may make, run and propagate covered works that you do not convey, 170 | without conditions so long as your license otherwise remains in force. 171 | You may convey covered works to others for the sole purpose of having 172 | them make modifications exclusively for you, or provide you with 173 | facilities for running those works, provided that you comply with the 174 | terms of this License in conveying all material for which you do not 175 | control copyright. 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Termination. 404 | 405 | You may not propagate or modify a covered work except as expressly 406 | provided under this License. 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Automatic Licensing of Downstream Recipients. 443 | 444 | Each time you convey a covered work, the recipient automatically 445 | receives a license from the original licensors, to run, modify and 446 | propagate that work, subject to this License. You are not responsible 447 | for enforcing compliance by third parties with this License. 448 | 449 | An "entity transaction" is a transaction transferring control of an 450 | organization, or substantially all assets of one, or subdividing an 451 | organization, or merging organizations. 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Patents. 468 | 469 | A "contributor" is a copyright holder who authorizes use under this 470 | License of the Program or a work on which the Program is based. The 471 | work thus licensed is called the contributor's "contributor version". 472 | 473 | A contributor's "essential patent claims" are all patent claims owned 474 | or controlled by the contributor, whether already acquired or 475 | hereafter acquired, that would be infringed by some manner, permitted 476 | by this License, of making, using, or selling its contributor version, 477 | but do not include claims that would be infringed only as a 478 | consequence of further modification of the contributor version. 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"Knowingly relying" means you have 504 | actual knowledge that, but for the patent license, your conveying the 505 | covered work in a country, or your recipient's use of the covered work 506 | in a country, would infringe one or more identifiable patents in that 507 | country that you have reason to believe are valid. 508 | 509 | If, pursuant to or in connection with a single transaction or 510 | arrangement, you convey, or propagate by procuring conveyance of, a 511 | covered work, and grant a patent license to some of the parties 512 | receiving the covered work authorizing them to use, propagate, modify 513 | or convey a specific copy of the covered work, then the patent license 514 | you grant is automatically extended to all recipients of the covered 515 | work and works based on it. 516 | 517 | A patent license is "discriminatory" if it does not include within the 518 | scope of its coverage, prohibits the exercise of, or is conditioned on 519 | the non-exercise of one or more of the rights that are specifically 520 | granted under this License. You may not convey a covered work if you 521 | are a party to an arrangement with a third party that is in the 522 | business of distributing software, under which you make payment to the 523 | third party based on the extent of your activity of conveying the 524 | work, and under which the third party grants, to any of the parties 525 | who would receive the covered work from you, a discriminatory patent 526 | license (a) in connection with copies of the covered work conveyed by 527 | you (or copies made from those copies), or (b) primarily for and in 528 | connection with specific products or compilations that contain the 529 | covered work, unless you entered into that arrangement, or that patent 530 | license was granted, prior to 28 March 2007. 531 | 532 | Nothing in this License shall be construed as excluding or limiting 533 | any implied license or other defenses to infringement that may 534 | otherwise be available to you under applicable patent law. 535 | 536 | #### 12. No Surrender of Others' Freedom. 537 | 538 | If conditions are imposed on you (whether by court order, agreement or 539 | otherwise) that contradict the conditions of this License, they do not 540 | excuse you from the conditions of this License. If you cannot convey a 541 | covered work so as to satisfy simultaneously your obligations under 542 | this License and any other pertinent obligations, then as a 543 | consequence you may not convey it at all. For example, if you agree to 544 | terms that obligate you to collect a royalty for further conveying 545 | from those to whom you convey the Program, the only way you could 546 | satisfy both those terms and this License would be to refrain entirely 547 | from conveying the Program. 548 | 549 | #### 13. Use with the GNU Affero General Public License. 550 | 551 | Notwithstanding any other provision of this License, you have 552 | permission to link or combine any covered work with a work licensed 553 | under version 3 of the GNU Affero General Public License into a single 554 | combined work, and to convey the resulting work. The terms of this 555 | License will continue to apply to the part which is the covered work, 556 | but the special requirements of the GNU Affero General Public License, 557 | section 13, concerning interaction through a network will apply to the 558 | combination as such. 559 | 560 | #### 14. Revised Versions of this License. 561 | 562 | The Free Software Foundation may publish revised and/or new versions 563 | of the GNU General Public License from time to time. Such new versions 564 | will be similar in spirit to the present version, but may differ in 565 | detail to address new problems or concerns. 566 | 567 | Each version is given a distinguishing version number. If the Program 568 | specifies that a certain numbered version of the GNU General Public 569 | License "or any later version" applies to it, you have the option of 570 | following the terms and conditions either of that numbered version or 571 | of any later version published by the Free Software Foundation. If the 572 | Program does not specify a version number of the GNU General Public 573 | License, you may choose any version ever published by the Free 574 | Software Foundation. 575 | 576 | If the Program specifies that a proxy can decide which future versions 577 | of the GNU General Public License can be used, that proxy's public 578 | statement of acceptance of a version permanently authorizes you to 579 | choose that version for the Program. 580 | 581 | Later license versions may give you additional or different 582 | permissions. However, no additional obligations are imposed on any 583 | author or copyright holder as a result of your choosing to follow a 584 | later version. 585 | 586 | #### 15. Disclaimer of Warranty. 587 | 588 | THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY 589 | APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT 590 | HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT 591 | WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT 592 | LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 593 | A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND 594 | PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE 595 | DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR 596 | CORRECTION. 597 | 598 | #### 16. Limitation of Liability. 599 | 600 | IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING 601 | WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR 602 | CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, 603 | INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES 604 | ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT 605 | NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR 606 | LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM 607 | TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER 608 | PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. 609 | 610 | #### 17. Interpretation of Sections 15 and 16. 611 | 612 | If the disclaimer of warranty and limitation of liability provided 613 | above cannot be given local legal effect according to their terms, 614 | reviewing courts shall apply local law that most closely approximates 615 | an absolute waiver of all civil liability in connection with the 616 | Program, unless a warranty or assumption of liability accompanies a 617 | copy of the Program in return for a fee. 618 | 619 | END OF TERMS AND CONDITIONS 620 | 621 | ### How to Apply These Terms to Your New Programs 622 | 623 | If you develop a new program, and you want it to be of the greatest 624 | possible use to the public, the best way to achieve this is to make it 625 | free software which everyone can redistribute and change under these 626 | terms. 627 | 628 | To do so, attach the following notices to the program. It is safest to 629 | attach them to the start of each source file to most effectively state 630 | the exclusion of warranty; and each file should have at least the 631 | "copyright" line and a pointer to where the full notice is found. 632 | 633 | 634 | Copyright (C) 635 | 636 | This program is free software: you can redistribute it and/or modify 637 | it under the terms of the GNU General Public License as published by 638 | the Free Software Foundation, either version 3 of the License, or 639 | (at your option) any later version. 640 | 641 | This program is distributed in the hope that it will be useful, 642 | but WITHOUT ANY WARRANTY; without even the implied warranty of 643 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 644 | GNU General Public License for more details. 645 | 646 | You should have received a copy of the GNU General Public License 647 | along with this program. If not, see . 648 | 649 | Also add information on how to contact you by electronic and paper 650 | mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands \`show w' and \`show c' should show the 661 | appropriate parts of the General Public License. Of course, your 662 | program's commands might be different; for a GUI interface, you would 663 | use an "about box". 664 | 665 | You should also get your employer (if you work as a programmer) or 666 | school, if any, to sign a "copyright disclaimer" for the program, if 667 | necessary. For more information on this, and how to apply and follow 668 | the GNU GPL, see . 669 | 670 | The GNU General Public License does not permit incorporating your 671 | program into proprietary programs. If your program is a subroutine 672 | library, you may consider it more useful to permit linking proprietary 673 | applications with the library. If this is what you want to do, use the 674 | GNU Lesser General Public License instead of this License. But first, 675 | please read . 676 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | - [About this project](#sec-1) 2 | - [About Direnv](#sec-1-1) 3 | - [About Nix integration](#sec-1-2) 4 | - [Installation](#sec-2) 5 | - [Nix package manager setup](#sec-2-1) 6 | - [Cache setup](#sec-2-2) 7 | - [Installation via `nix-env`](#install-nixenv) 8 | - [Direnv installation](#sec-2-3-1) 9 | - [Installing Lorelei](#sec-2-3-2) 10 | - [Installation via Home Manager](#install-homemanager) 11 | - [Configuration and usage](#sec-3) 12 | - [Terminal and editor configuration](#sec-3-1) 13 | - [Per-project configuration](#sec-3-2) 14 | - [Prior art](#sec-4) 15 | - [Known limitations](#sec-5) 16 | - [Release](#sec-6) 17 | - [License](#sec-7) 18 | - [Contribution](#sec-8) 19 | 20 | [![img](https://github.com/shajra/direnv-nix-lorelei/workflows/CI/badge.svg)](https://github.com/shajra/direnv-nix-lorelei/actions) 21 | 22 | # About this project 23 | 24 | Lorelei provides a [Direnv](https://direnv.net) extension to configure directory-level environment variables from a [Nix](https://nixos.org/nix) expression. This support improves upon the built-in Nix support of Direnv with the following features: 25 | 26 | - The calculation of your project's environment variables can be cached to avoid loading time. 27 | 28 | - The cache of environment variables can be configured to be invalidated when 29 | - the content of a file changes 30 | - a file's modification time changes (even if content does not) 31 | - a per-project `.direnv/delete_to_rebuild` file is deleted. 32 | 33 | - Additionally files to watch for cache invalidation can be automatically detected, though this detection is not comprehensive. 34 | 35 | - Programs referenced by active environment variables are prevented from being garbage collected by Nix. 36 | 37 | - You can also save a configurable number of previous environments from being garbage collected. 38 | 39 | Note, Lorelei only works with projects that have a Nix file that can be called with `nix-shell` (typically called "shell.nix"). For projects that provide a Nix environment with the not-yet-released Nix flakes feature, please consider using the `use_flake` function of the [nix-direnv](https://github.com/nix-community/nix-direnv) project, which you can use concurrently with Lorelei with no conflicts. 40 | 41 | ## About Direnv 42 | 43 | When we go into a project's directory we often want certain environment variables set specifically to a project's needs. A very common environment variable to specify per-project is `PATH` to make available development tools needed by a project. Different projects may depend on conflicting tools, such as different versions of a compiler. 44 | 45 | Direnv targets solving this problem. Once you set it up, you can hook your terminal shell to automatically load variables based upon your current working directory. Then, when you `cd` into the directory, the variables change automatically. 46 | 47 | Additionally, many popularly used programming editors have Direnv extensions/plugins. Rather than use editor-specific configuration to treat each project differently, we can configure these projects with Direnv. Any editor configured with a Direnv extension/plugin will then pick up the right environment based on the project of the edited file. 48 | 49 | Once we set up our editors and shells with Direnv, we can configure our project-specific environment in one place with Direnv. Also, since Nix is far less popularly used than Direnv, we don't have to worry about unsupported Nix integration with our editors or shells. Lorelei can provide all the Nix support we need for Direnv. 50 | 51 | ## About Nix integration 52 | 53 | Nix is a package manager (in the same sense as APT, RPM, Homebrew, or Chocolatey). As a package manager, Nix helps us get tools and libraries installed on our system. Nix goes a bit farther, by providing us some facilities to help us get these tools set up in a local environment called a *Nix shell*. 54 | 55 | We typically go into a directory with with a specially configured `shell.nix` file, and execute `nix-shell` to enter into an interactive Bash session with environment variables set up for working in our project. 56 | 57 | Direnv can help us get rid of the extra step of having to call `nix-shell`. 58 | 59 | Direnv actually comes with Nix support built-in, but this support is very basic. Specifically, it has no caching of calculated environments, or protection required dependencies from being garbage collected by Nix. 60 | 61 | See [the provided documentation on Nix](doc/nix.md) for more on what Nix is, why we're motivated to use it, and how to get set up with it for this project. Not covered in this documentation are details on how to set make a Nix expression to set up a Nix shell. There's just a lot of ways to do this for each programming langauge, and the [official Nixpkgs manual](https://nixos.org/nixpkgs/manual) is the best resource. 62 | 63 | # Installation 64 | 65 | Lorelei should work with either GNU/Linux or MacOS operating systems. Before we can configure specific projects/directories to use Direnv and Lorelei, we need to do the following: 66 | 67 | 1. install and configure Nix, if we haven't already 68 | 2. install Direnv 69 | 3. install Lorelei 70 | 4. create a symlink under `$XDG_CONFIG_HOME/direnv/lib` pointing to Lorelei's installed Bash functions. 71 | 72 | Beyond the installation of Nix, we have two ways to install packages and create the symlink: 73 | 74 | - use `nix-env` and create the symlink ourselves 75 | - use [Home Manager](https://github.com/nix-community/home-manager) to manage both packages and home directory configuration (including the symlink under under `$XDG_CONFIG_HOME/direnv/lib`). 76 | 77 | The following sections cover both these options. Home Manager introduces its own complexity and added work for configuration. But there can be a nice payoff if you opt to use Home Manager to manage more than just Lorelei. 78 | 79 | ## Nix package manager setup 80 | 81 | > **NOTE:** You don't need this step if you're running NixOS, which comes with Nix baked in. 82 | 83 | If you don't already have Nix, [the official installation script](https://nixos.org/learn.html) should work on a variety of UNIX-like operating systems: 84 | 85 | ```bash 86 | sh <(curl -L https://nixos.org/nix/install) --daemon 87 | ``` 88 | 89 | If you're on a recent release of MacOS, you will need an extra switch: 90 | 91 | ```bash 92 | sh <(curl -L https://nixos.org/nix/install) --daemon \ 93 | --darwin-use-unencrypted-nix-store-volume 94 | ``` 95 | 96 | After installation, you may have to exit your terminal session and log back in to have environment variables configured to put Nix executables on your `PATH`. 97 | 98 | The `--daemon` switch installs Nix in the recommended multi-user mode. This requires the script to run commands with `sudo`. The script fairly verbosely reports everything it does and touches. If you later want to uninstall Nix, you can run the installation script again, and it will tell you what to do to get back to a clean state. 99 | 100 | The Nix manual describes [other methods of installing Nix](https://nixos.org/nix/manual/#chap-installation) that may suit you more. 101 | 102 | ## Cache setup 103 | 104 | It's recommended to configure Nix to use shajra.cachix.org as a Nix *substitutor*. This project pushes built Nix packages to [Cachix](https://cachix.org) as part of its continuous integration. Once configured, Nix will pull down these pre-built packages instead of building them locally (potentially saving a lot of time). This augments the default substitutor that pulls from cache.nixos.org. 105 | 106 | You can configure shajra.cachix.org as a substitutor with the following command: 107 | 108 | ```sh 109 | nix run \ 110 | --file https://cachix.org/api/v1/install \ 111 | cachix \ 112 | --command cachix use shajra 113 | ``` 114 | 115 | Cachix is a service that anyone can use. You can call this command later to add substitutors for someone else using Cachix, replacing "shajra" with their cache's name. 116 | 117 | If you've just run a multi-user Nix installation and are not yet a trusted user in `/etc/nix/nix.conf`, this command may not work. But it will report back some options to proceed. 118 | 119 | One option sets you up as a trusted user, and installs Cachix configuration for Nix locally at `~/.config/nix/nix.conf`. This configuration will be available immediately, and any subsequent invocation of Nix commands will take advantage of the Cachix cache. 120 | 121 | You can alternatively configure Cachix as a substitutor globally by running the above command as a root user (say with `sudo`), which sets up Cachix directly in `/etc/nix/nix.conf`. The invocation may give further instructions upon completion. 122 | 123 | ## Installation via `nix-env` 124 | 125 | This section covers the option of installing packages with `nix-env`, and not with Home Manager. If you're not as familiar with `nix-env`, you may be interested in this project's [supplemental documentation on Nix](doc/nix.md). 126 | 127 | If you've installed Home Manager, you may skip this section and try out [the next section on installation with Home manager](#install-homemanager). 128 | 129 | ### Direnv installation 130 | 131 | If you don't already have Direnv installed, you have the option of installing Direnv from this project (otherwise, you can skip this step): 132 | 133 | ```sh 134 | nix-env --install --file . --attr direnv 2>&1 135 | ``` 136 | 137 | installing 'direnv-2.28.0' 138 | 139 | If you have `~/.nix-profile/bin` in your environment's `PATH`, you should be able to call the `direnv` executable. Here's a simple way of testing its availability. 140 | 141 | ```sh 142 | direnv version 143 | ``` 144 | 145 | 2.28.0 146 | 147 | ### Installing Lorelei 148 | 149 | This project provides a Nix expression in the project's root `default.nix` file. From the root directory of a checkout of the project, you can install Lorelei as follows: 150 | 151 | ```sh 152 | nix-env --install --file . --attr direnv-nix-lorelei 2>&1 153 | ``` 154 | 155 | installing 'direnv-nix-lorelei' 156 | 157 | This installation doesn't install a binary, but instead a shell library that you use as configuration for Direnv. Given a typical installation of Nix, this installation should be into the active Nix profile at `~/.nix-profile`. We can tie this library to Direnv with a symlink: 158 | 159 | ```sh 160 | mkdir --parents ~/.config/direnv/lib 161 | ln --force --symbolic --no-target-directory \ 162 | ~/.nix-profile/share/direnv-nix-lorelei/nix-lorelei.bash \ 163 | ~/.config/direnv/lib/nix-lorelei.sh 164 | ``` 165 | 166 | ## Installation via Home Manager 167 | 168 | This section is for those those who are interested in Home Manager, and skipped [the prior section](#install-nixenv) on how to install the needed packages with `nix-env` and create the needed symlink directly with `ln`. 169 | 170 | Detailed instructions on the installation of Home Manager are beyond the scope of this document. Please refer to [Home Manager's manual](https://rycee.gitlab.io/home-manager/). 171 | 172 | Home Manager is configured with NixOS-style modules. These modules are Nix functions of a certain form. Modules can import other modules by their path. Some modules provide an configuration options, which are then imported by other modules on the user's side where these options are then employed to configure a particular machine. 173 | 174 | In our case, this project provides a module at the *attribute path* `direnv-nix-lorelei-home`. To configure a machine with Lorelei using Home Manager, we'll import this module, and then enable the provided options. Here's an commented example of such a configuration: 175 | 176 | ```nix 177 | { config, pkgs, lib, ... }: 178 | 179 | let 180 | 181 | # First we have to get the Lorelei source code from GitHub. 182 | 183 | # Unfortunately, can't use pkgs from above (infinite recursion) 184 | pkgs-bootstrap = import { config = {}; overlays = []; }; 185 | 186 | lorelei-source = pkgs-bootstrap.fetchFromGitHub { 187 | owner = "shajra"; 188 | repo = "direnv-nix-lorelei"; 189 | 190 | # This is example Git commit ID to pin to. Choose another to upgrade to 191 | # a later version of Lorelei. 192 | rev = "8310119578f9bcedb1e4ca2580d3b11bd7d214f2"; 193 | 194 | # Use pkgs.lib.fakeSha256 the first time using a new rev with Home 195 | # Manager, which will then report back the real value to use. A real 196 | # value will look something like this: sha256 = 197 | # "198h7ryqdv0h9lv3sixqxzdl8wf57lsvzzm8viipmk4pb0lsyckh"; 198 | sha256 = lib.fakeSha256; 199 | }; 200 | 201 | # Then we access the module it provides. 202 | module-lorelei = (import lorelei-source).direnv-nix-lorelei-home; 203 | 204 | in 205 | 206 | # Here's where we configure options provided by imported modules. As is typical, 207 | # the final modules used to configure a machine don't create more options. 208 | { 209 | # Here our configuration module imports the module Lorelei provides. 210 | imports = [ module-lorelei ]; 211 | 212 | # Home manager already has a module that allows us to include Direnv on our 213 | # user's PATH. 214 | programs.direnv.enable = true; 215 | 216 | # Here we enable the option to have Home Manager set up the symlink under 217 | # $XDG_CONFIG_HOME/direnv/lib to enable Lorelei's usage with Direnv. 218 | programs.direnv-nix-lorelei.enable = true; 219 | } 220 | ``` 221 | 222 | Not completely illustrated in the above example, the Lorelei Home Manager module provides two options: 223 | 224 | - `programs.direnv-nix-lorelei.enable`: to install Lorelei and configure Direnv to use it. 225 | - `programs.direnv-nix-lorelei.package`: in case you want to specify another version of Lorelei to use on the machine. 226 | 227 | If you're curious, you can read [the source code of the module](nix/home.nix) to see the specifications for these options. 228 | 229 | The example above has you going through a step to use `lib.fakeSha256` to get the real hash for Lorelei. These hashes are an important part of Nix's model of trusted code, but managing them when updating dependencies can be a chore. Eventually [Nix Flakes](https://nixos.wiki/wiki/Flakes) will release, which will help with that. In the meantime, you may be interested in the [Niv](https://github.com/nmattia/niv) project to manage these hashes when updating dependencies. 230 | 231 | If further interested, you may like looking at [a larger example](https://github.com/shajra/shajra-provisioning/blob/master/home/modules/base/default.nix) of Home Manager configuration of much more than just Lorelei. 232 | 233 | # Configuration and usage 234 | 235 | ## Terminal and editor configuration 236 | 237 | If you're absolutely new to Direnv, we won't get any benefit from the configuration described in this document until we integrate Direnv with either our terminal's shell, our editor of choice, or both. 238 | 239 | We delegate to the [official Direnv documentation](https://direnv.net/#docs) on how to do this configuration. Specifically, have a look at 240 | 241 | - [hooking Direnv into your preferred shell](https://direnv.net/docs/hook.html) 242 | - the [Direnv wiki for pages about editor integration](https://github.com/direnv/direnv/wiki#editor-integration). 243 | 244 | ## Per-project configuration 245 | 246 | If you have a project that can be used to enter a Nix shell with a call like 247 | 248 | ```sh 249 | nix-shell "$NIX_FILE" 250 | ``` 251 | 252 | for some file `$NIX_FILE`, then at the root of the project you can create a `.envrc` to get started with Direnv: 253 | 254 | ```sh 255 | echo "use_nix_gcrooted -a \"$NIX_FILE\"" > .envrc 256 | ``` 257 | 258 | As with `nix-shell` specifying a Nix file as a positional argument is optional if you're file is called `shell.nix`. Furthermore, if you don't use `shell.nix`, but use `default.nix` it is also optional. 259 | 260 | Finally, we can activate the configuration (Direnv has some security measures to prevent abuse from running arbitrary scripts): 261 | 262 | ```sh 263 | direnv allow 264 | ``` 265 | 266 | At this point, if you have your terminal and editor configured to use Direnv, you should experience per-project environments serviced by Direnv. 267 | 268 | To learn more more about Lorelei's options, we can source the script and run the function outside Direnv. However, we need to be in a Bash shell: 269 | 270 | ```sh 271 | bash -c " 272 | . ~/.nix-profile/share/direnv-nix-lorelei/nix-lorelei.bash 273 | use_nix_gcrooted --help 274 | " 275 | ``` 276 | 277 | USAGE: use_nix_gcrooted [OPTION]... [FILE] 278 | 279 | DESCRIPTION: 280 | 281 | A replacement for Direnv's use_nix. This function, will make 282 | sure calculated Nix expressions are GC rooted with Nix. By 283 | default the calculated environment is also cached, which is 284 | useful for Nix expressions that have costly evaluations. To 285 | invalidate the cache, files can be watched either by their 286 | content hash or their modification time. You can also delete 287 | .direnv/delete_to_rebuild to invalidate the cache. 288 | 289 | OPTIONS: 290 | 291 | -h --help print this help message 292 | -a --auto-watch-content watch autodetected files for contect 293 | changes 294 | -A --auto-watch-mtime watch autodetected files for 295 | modification times 296 | -d --auto-watch-deep deeper searching for -a and -A options 297 | -w --watch-content PATH watch a file's content for changes 298 | -W --watch-mtime PATH watch a file's modification time 299 | -C --ignore-cache recompute new environment every time 300 | -k --keep-last NUM protect last N caches from GC 301 | (default 5) 302 | 303 | Direnv needs to know when to consider recalculating an environment's variables. To do this, we need to register files to watch for changes. This is what the "watch" switches above help specify. 304 | 305 | With the `--auto-watch-content` and `--auto-watch-mtime` switches, you don't have to worry about which files to watch for changes. You can either watch these files when their modifications time change, or when their content actually changes (touching a file changes its modification time, but not its content). 306 | 307 | The `--auto-watch-content` and `--auto-watch-mtime` switches catch a good amount of Nix files, but won't catch everything you might have the idea to watch. If you want to specify files to watch explicitly, you can use the `--watch-content` and `--watch-mtime` switches. 308 | 309 | You can use the `--auto-watch-deep` switch to have the auto-watching features look a little deeper for files to watch. However, the evaluation time you'll face for an not-yet-cached environment will be notably longer for this deeper search (possibly twice as long). Note auto-watching without the `--auto-watch-deep` switch shouldn't add much evaluation overhead, so you should be able to use the normal shallower auto-detection without worrying about a slowdown. 310 | 311 | If for some (unlikely) reason, you want the benefits of protection from Nix garbage collection, but not cache the evaluation of environments, you can use `--ignore-cache`. Note, that you still need to specify files to watch for changes. With `--ignore-cache`, you'll recalculate the Nix expression for your project every time these watched files trigger Direnv to recalculate an environment. 312 | 313 | Lorelei keeps the last five environments from being garbage collected. You can change this with `--keep-last`. 314 | 315 | And finally, if you ever feel like you want to dump your cached environment and recalculate everything, just delete `.direnv/delete_to_rebuild`, which will be next to your project's `.envrc` file. 316 | 317 | Lorelei's metadata for your project is in two places: 318 | 319 | - your project's `.direnv` directory 320 | - your user's GC root directory: `/nix/var/nix/gcroots/per-user/$USER` 321 | 322 | You can delete this data to start fresh. 323 | 324 | The symlinks in the GC root directory have human readable names to assist manual curation if you need it. 325 | 326 | # Prior art 327 | 328 | There are four projects that were considered before writing Lorelei: 329 | 330 | - [Lorri](https://github.com/target/lorri) 331 | - [Sorri](https://github.com/nmattia/sorri) 332 | - [Nix-direnv](https://github.com/nix-community/nix-direnv) 333 | - [Nixify](https://github.com/kalbasit/nur-packages/blob/master/pkgs/nixify/envrc) 334 | 335 | Lorelei should subsume the features of all of these projects with the exception of Lorri's approach to calculating Direnv environments as a background process. You can think of the name "Lorelei" as a pun of "Lorri-lite," but "Lorelei" is also the name of a [Pogue's song](https://www.youtube.com/watch?v=VDw81PRP2SQ) you may enjoy. 336 | 337 | All of these different projects can save on the evaluation time of calculating a Nix expression by caching the Direnv environment. And all of these projects have some facility to protect dependencies referenced by Direnv environments from Nix's garbage collection. 338 | 339 | Lorri is the heaviest of these options. To use it, you start a daemon process that in the background watches files for changes and evaluates/builds environments. This way, the environment is ready before you actually enter the project. 340 | 341 | Also Lorri inspects Nix's build log to automatically detect which files need to be watched for changes. Unfortunately, this often misses useful files to watch in a project. 342 | 343 | Running a background process can be a heavy extra process, and introduces the surface area of complexity and exposure to defects (though the Lorri committers have been committed to fixing them). All of the other projects are lighter-weight than Lorri in this regard. They are just scripts with no requirements on a background process. 344 | 345 | Sorri copies a lot of code from Lorri, but removes the background process. So when you enter a Direnv directory, you will always experience the evaluation time of calculating a not-yet-cached Direnv environment. With Lorri this evaluation occurs in the background. 346 | 347 | Lorelei is different from Sorri in two main ways: 348 | 349 | - Lorelei gives much more control of cache invalidation beyond the auto-detection of files to watch for changes. These approaches are inspired by Nix-direnv and Nixify. 350 | 351 | - Rather than copying code from Lorri, we actually call Lorri code directly as a library. 352 | 353 | Lorri has been relatively active about refining the approach to calculating a Direnv environment, more so than any of the other projects. Sorri copies code, but leads to more work porting changes from Lorri to Sorri. Lorelei uses Nix to use Lorri's code directly. This eases maintenance, but does mean that you *have* to install Lorelei with Nix. However, this is not a bad idea, because Lorelei rigorously pins all of its dependencies, all the way down to `coreutils`. So by installing Lorelei with Nix, we get more precision. 354 | 355 | # Known limitations 356 | 357 | There's two known limitations of Lorelei: 358 | 359 | - Your project must have a Nix file that can be run with `nix-shell`. 360 | - Nix flakes aren't supported (yet). 361 | 362 | Lorelei delegates strongly to Lorri, so the limitation of requiring an explicit Nix file to import stems from that. This is not to say that this limitation can't be improved upon in the future. 363 | 364 | However, we probably don't want to support something like `nix-shell`'s `--packages` switch. This feature of `nix-shell` is generally discouraged by the Nix community because its implementation has a lot of non-intuitive warts. Nix will soon release a `nix shell` command that has the potential to more properly replace the functionality that `nix-shell`'s `--packages` switch provides. When this occurs, both the Lorri and Lorelei can reevaluate their respective implementation strategies. 365 | 366 | Also, soon to be released in a new version of Nix are [Nix flakes](https://nixos.wiki/wiki/Flakes). If you don't know what flakes are, you may want to wait until they stabilize and are officially released. If you're an early adopter of flakes, the [Nix-direnv](https://github.com/nix-community/nix-direnv) project has support for Nix flakes with it's `use_flake` function. Lorelei can be installed and used concurrently with other projects offering similar functionality (Lorri, Nix-direnv, and the rest). You just make different calls in your project's `.envrc` files. No core contributor of Lorelei is using this unreleased version of Nix supporting flakes, so we didn't want to provide something we had not tested ourselves. 367 | 368 | # Release 369 | 370 | The "main" branch of the repository on GitHub has the latest released version of this code. There is currently no commitment to either forward or backward compatibility. 371 | 372 | "user/shajra" branches are personal branches that may be force-pushed to. The "main" branch should not experience force-pushes and is recommended for general use. 373 | 374 | # License 375 | 376 | All files in this "direnv-nix-lorelei" project are licensed under the terms of GPLv3 or (at your option) any later version. 377 | 378 | Please see the [./COPYING.md](./COPYING.md) file for more details. 379 | 380 | # Contribution 381 | 382 | Feel free to file issues and submit pull requests with GitHub. 383 | 384 | There is only one author to date, so the following copyright covers all files in this project: 385 | 386 | Copyright © 2020 Sukant Hajra 387 | -------------------------------------------------------------------------------- /README.org: -------------------------------------------------------------------------------- 1 | #+title: Lorelei, an Alternative Nix extension of Direnv 2 | #+setupfile: doc/links.org 3 | 4 | [[https://github.com/shajra/direnv-nix-lorelei/actions][https://github.com/shajra/direnv-nix-lorelei/workflows/CI/badge.svg]] 5 | 6 | * Org-mode setup :noexport: 7 | 8 | ** Formatting help 9 | 10 | This snippet can be used as a post-processing step to crop down the results from 11 | an evaluation of a source code block. 12 | 13 | #+name: drop 14 | #+begin_src emacs-lisp :var text="" :var n-dropped=0 :results silent 15 | (string-join (-drop n-dropped (split-string text "\n")) "\n") 16 | #+end_src 17 | 18 | ** Setup action 19 | 20 | The following helps (using Noweb) set up Nix environment variables for source 21 | block evaluation. 22 | 23 | #+name: nix-init 24 | #+begin_src sh :eval no 25 | export NIX_PROFILE=$(pwd)/nix-profile 26 | export NIX_PAGER=cat 27 | export PATH="$NIX_PROFILE/bin:$PATH" 28 | #+end_src 29 | 30 | Next we perform some side-effects to set up the evaluation of the whole 31 | document. 32 | 33 | #+name: cleanup 34 | #+begin_src sh :results output silent :noweb yes 35 | <> 36 | rm --force result* 37 | rm --force "$NIX_PROFILE"* 38 | #+end_src 39 | 40 | This is just a hack to deal with the fact that we never know what directory a 41 | session will start in, so we need a way to calculate the PWD to jump to it. 42 | 43 | #+name: pwd 44 | #+begin_src sh :results output silent 45 | echo cd "$(pwd)" 46 | #+end_src 47 | 48 | This begins a session with environment variables initialized. 49 | 50 | #+name: session-init 51 | #+begin_src sh :session env :results output silent :noweb yes 52 | <> 53 | <> 54 | #+end_src 55 | 56 | * About this project 57 | 58 | Lorelei provides a [[direnv][Direnv]] extension to configure directory-level environment 59 | variables from a [[nix][Nix]] expression. This support improves upon the built-in Nix 60 | support of Direnv with the following features: 61 | 62 | - The calculation of your project's environment variables can be cached to avoid 63 | loading time. 64 | 65 | - The cache of environment variables can be configured to be invalidated when 66 | - the content of a file changes 67 | - a file's modification time changes (even if content does not) 68 | - a per-project =.direnv/delete_to_rebuild= file is deleted. 69 | 70 | - Additionally files to watch for cache invalidation can be automatically 71 | detected, though this detection is not comprehensive. 72 | 73 | - Programs referenced by active environment variables are prevented from being 74 | garbage collected by Nix. 75 | 76 | - You can also save a configurable number of previous environments from being 77 | garbage collected. 78 | 79 | Note, Lorelei only works with projects that have a Nix file that can be called 80 | with =nix-shell= (typically called "shell.nix"). For projects that provide a Nix 81 | environment with the not-yet-released Nix flakes feature, please consider using 82 | the =use_flake= function of the [[nixdirenv][nix-direnv]] project, which you can use 83 | concurrently with Lorelei with no conflicts. 84 | 85 | ** About Direnv 86 | 87 | When we go into a project's directory we often want certain environment 88 | variables set specifically to a project's needs. A very common environment 89 | variable to specify per-project is =PATH= to make available development tools 90 | needed by a project. Different projects may depend on conflicting tools, such as 91 | different versions of a compiler. 92 | 93 | Direnv targets solving this problem. Once you set it up, you can hook your 94 | terminal shell to automatically load variables based upon your current working 95 | directory. Then, when you ~cd~ into the directory, the variables change 96 | automatically. 97 | 98 | Additionally, many popularly used programming editors have Direnv 99 | extensions/plugins. Rather than use editor-specific configuration to treat each 100 | project differently, we can configure these projects with Direnv. Any editor 101 | configured with a Direnv extension/plugin will then pick up the right 102 | environment based on the project of the edited file. 103 | 104 | Once we set up our editors and shells with Direnv, we can configure our 105 | project-specific environment in one place with Direnv. Also, since Nix is far 106 | less popularly used than Direnv, we don't have to worry about unsupported Nix 107 | integration with our editors or shells. Lorelei can provide all the Nix support 108 | we need for Direnv. 109 | 110 | ** About Nix integration 111 | 112 | Nix is a package manager (in the same sense as APT, RPM, Homebrew, or 113 | Chocolatey). As a package manager, Nix helps us get tools and libraries 114 | installed on our system. Nix goes a bit farther, by providing us some facilities 115 | to help us get these tools set up in a local environment called a /Nix shell/. 116 | 117 | We typically go into a directory with with a specially configured =shell.nix= 118 | file, and execute ~nix-shell~ to enter into an interactive Bash session with 119 | environment variables set up for working in our project. 120 | 121 | Direnv can help us get rid of the extra step of having to call =nix-shell=. 122 | 123 | Direnv actually comes with Nix support built-in, but this support is very basic. 124 | Specifically, it has no caching of calculated environments, or protection 125 | required dependencies from being garbage collected by Nix. 126 | 127 | See [[file:doc/nix.org][the provided documentation on Nix]] for more on what Nix is, why we're 128 | motivated to use it, and how to get set up with it for this project. Not covered 129 | in this documentation are details on how to set make a Nix expression to set up 130 | a Nix shell. There's just a lot of ways to do this for each programming 131 | langauge, and the [[nixpkgs-manual][official Nixpkgs manual]] is the best resource. 132 | 133 | * Installation 134 | 135 | Lorelei should work with either GNU/Linux or MacOS operating systems. Before we 136 | can configure specific projects/directories to use Direnv and Lorelei, we need 137 | to do the following: 138 | 139 | 1. install and configure Nix, if we haven't already 140 | 2. install Direnv 141 | 3. install Lorelei 142 | 4. create a symlink under =$XDG_CONFIG_HOME/direnv/lib= pointing to Lorelei's 143 | installed Bash functions. 144 | 145 | Beyond the installation of Nix, we have two ways to install packages and create 146 | the symlink: 147 | 148 | - use =nix-env= and create the symlink ourselves 149 | - use [[homemanager][Home Manager]] to manage both packages and home directory configuration 150 | (including the symlink under under =$XDG_CONFIG_HOME/direnv/lib=). 151 | 152 | The following sections cover both these options. Home Manager introduces its own 153 | complexity and added work for configuration. But there can be a nice payoff if 154 | you opt to use Home Manager to manage more than just Lorelei. 155 | 156 | #+include: "doc/nix.org::*Nix package manager setup" 157 | 158 | #+include: "doc/nix.org::*Cache setup" 159 | 160 | ** Installation via =nix-env= 161 | :PROPERTIES: 162 | :CUSTOM_ID: install-nixenv 163 | :END: 164 | 165 | This section covers the option of installing packages with =nix-env=, and not 166 | with Home Manager. If you're not as familiar with =nix-env=, you may be 167 | interested in this project's [[file:doc/nix.org][supplemental documentation on Nix]]. 168 | 169 | If you've installed Home Manager, you may skip this section and try out [[#install-homemanager][the next 170 | section on installation with Home manager]]. 171 | 172 | *** Direnv installation 173 | 174 | If you don't already have Direnv installed, you have the option of installing 175 | Direnv from this project (otherwise, you can skip this step): 176 | 177 | #+name: direnv-install 178 | #+begin_src sh :session env :results output :exports both 179 | nix-env --install --file . --attr direnv 2>&1 180 | #+end_src 181 | 182 | #+results: direnv-install 183 | : installing 'direnv-2.28.0' 184 | 185 | If you have =~/.nix-profile/bin= in your environment's =PATH=, you should be 186 | able to call the =direnv= executable. Here's a simple way of testing its 187 | availability. 188 | 189 | #+name: direnv-version 190 | #+begin_src sh :session env :results output :exports both 191 | direnv version 192 | #+end_src 193 | 194 | #+results: direnv-version 195 | : 2.28.0 196 | 197 | *** Installing Lorelei 198 | 199 | This project provides a Nix expression in the project's root =default.nix= file. 200 | From the root directory of a checkout of the project, you can install Lorelei as 201 | follows: 202 | 203 | #+name: lorelei-install 204 | #+begin_src sh :session env :results output :exports both 205 | nix-env --install --file . --attr direnv-nix-lorelei 2>&1 206 | #+end_src 207 | 208 | #+results: lorelei-install 209 | : installing 'direnv-nix-lorelei' 210 | 211 | This installation doesn't install a binary, but instead a shell library that you 212 | use as configuration for Direnv. Given a typical installation of Nix, this 213 | installation should be into the active Nix profile at =~/.nix-profile=. We can 214 | tie this library to Direnv with a symlink: 215 | 216 | #+begin_src sh :eval no 217 | mkdir --parents ~/.config/direnv/lib 218 | ln --force --symbolic --no-target-directory \ 219 | ~/.nix-profile/share/direnv-nix-lorelei/nix-lorelei.bash \ 220 | ~/.config/direnv/lib/nix-lorelei.sh 221 | #+end_src 222 | 223 | ** Installation via Home Manager 224 | :PROPERTIES: 225 | :CUSTOM_ID: install-homemanager 226 | :END: 227 | 228 | This section is for those those who are interested in Home Manager, and skipped 229 | [[#install-nixenv][the prior section]] on how to install the needed packages with =nix-env= and 230 | create the needed symlink directly with =ln=. 231 | 232 | Detailed instructions on the installation of Home Manager are beyond the scope 233 | of this document. Please refer to [[homemanager-manual][Home Manager's manual]]. 234 | 235 | Home Manager is configured with NixOS-style modules. These modules are Nix 236 | functions of a certain form. Modules can import other modules by their path. 237 | Some modules provide an configuration options, which are then imported by other 238 | modules on the user's side where these options are then employed to configure a 239 | particular machine. 240 | 241 | In our case, this project provides a module at the /attribute path/ 242 | =direnv-nix-lorelei-home=. To configure a machine with Lorelei using Home 243 | Manager, we'll import this module, and then enable the provided options. Here's 244 | an commented example of such a configuration: 245 | 246 | #+begin_src nix :eval no 247 | { config, pkgs, lib, ... }: 248 | 249 | let 250 | 251 | # First we have to get the Lorelei source code from GitHub. 252 | 253 | # Unfortunately, can't use pkgs from above (infinite recursion) 254 | pkgs-bootstrap = import { config = {}; overlays = []; }; 255 | 256 | lorelei-source = pkgs-bootstrap.fetchFromGitHub { 257 | owner = "shajra"; 258 | repo = "direnv-nix-lorelei"; 259 | 260 | # This is example Git commit ID to pin to. Choose another to upgrade to 261 | # a later version of Lorelei. 262 | rev = "8310119578f9bcedb1e4ca2580d3b11bd7d214f2"; 263 | 264 | # Use pkgs.lib.fakeSha256 the first time using a new rev with Home 265 | # Manager, which will then report back the real value to use. A real 266 | # value will look something like this: sha256 = 267 | # "198h7ryqdv0h9lv3sixqxzdl8wf57lsvzzm8viipmk4pb0lsyckh"; 268 | sha256 = lib.fakeSha256; 269 | }; 270 | 271 | # Then we access the module it provides. 272 | module-lorelei = (import lorelei-source).direnv-nix-lorelei-home; 273 | 274 | in 275 | 276 | # Here's where we configure options provided by imported modules. As is typical, 277 | # the final modules used to configure a machine don't create more options. 278 | { 279 | # Here our configuration module imports the module Lorelei provides. 280 | imports = [ module-lorelei ]; 281 | 282 | # Home manager already has a module that allows us to include Direnv on our 283 | # user's PATH. 284 | programs.direnv.enable = true; 285 | 286 | # Here we enable the option to have Home Manager set up the symlink under 287 | # $XDG_CONFIG_HOME/direnv/lib to enable Lorelei's usage with Direnv. 288 | programs.direnv-nix-lorelei.enable = true; 289 | } 290 | #+end_src 291 | 292 | Not completely illustrated in the above example, the Lorelei Home Manager module 293 | provides two options: 294 | - =programs.direnv-nix-lorelei.enable=: to install Lorelei and configure Direnv 295 | to use it. 296 | - =programs.direnv-nix-lorelei.package=: in case you want to specify another 297 | version of Lorelei to use on the machine. 298 | 299 | If you're curious, you can read [[file:nix/home.nix][the source code of the module]] to see the 300 | specifications for these options. 301 | 302 | The example above has you going through a step to use =lib.fakeSha256= to get 303 | the real hash for Lorelei. These hashes are an important part of Nix's model of 304 | trusted code, but managing them when updating dependencies can be a chore. 305 | Eventually [[nix-flakes][Nix Flakes]] will release, which will help with that. In the meantime, 306 | you may be interested in the [[niv][Niv]] project to manage these hashes when updating 307 | dependencies. 308 | 309 | If further interested, you may like looking at [[shajra-provisioning-base][a larger example]] of Home Manager 310 | configuration of much more than just Lorelei. 311 | 312 | * Configuration and usage 313 | 314 | ** Terminal and editor configuration 315 | 316 | If you're absolutely new to Direnv, we won't get any benefit from the 317 | configuration described in this document until we integrate Direnv with either 318 | our terminal's shell, our editor of choice, or both. 319 | 320 | We delegate to the [[direnv-docs][official Direnv documentation]] on how to do this 321 | configuration. Specifically, have a look at 322 | - [[direnv-shell][hooking Direnv into your preferred shell]] 323 | - the [[direnv-editor][Direnv wiki for pages about editor integration]]. 324 | 325 | ** Per-project configuration 326 | 327 | If you have a project that can be used to enter a Nix shell with a call like 328 | 329 | #+begin_src sh :eval no 330 | nix-shell "$NIX_FILE" 331 | #+end_src 332 | 333 | for some file =$NIX_FILE=, then at the root of the project you can create a 334 | =.envrc= to get started with Direnv: 335 | 336 | #+begin_src sh :eval no 337 | echo "use_nix_gcrooted -a \"$NIX_FILE\"" > .envrc 338 | #+end_src 339 | 340 | As with =nix-shell= specifying a Nix file as a positional argument is optional 341 | if you're file is called =shell.nix=. Furthermore, if you don't use =shell.nix=, 342 | but use =default.nix= it is also optional. 343 | 344 | Finally, we can activate the configuration (Direnv has some security measures to 345 | prevent abuse from running arbitrary scripts): 346 | 347 | #+begin_src sh :eval no 348 | direnv allow 349 | #+end_src 350 | 351 | At this point, if you have your terminal and editor configured to use Direnv, 352 | you should experience per-project environments serviced by Direnv. 353 | 354 | To learn more more about Lorelei's options, we can source the script and run the 355 | function outside Direnv. However, we need to be in a Bash shell: 356 | 357 | #+begin_src sh :eval no 358 | bash -c " 359 | . ~/.nix-profile/share/direnv-nix-lorelei/nix-lorelei.bash 360 | use_nix_gcrooted --help 361 | " 362 | #+end_src 363 | 364 | #+name: help 365 | #+begin_src sh :session env :results output :exports results :post drop(text=*this*, n-dropped=2) 366 | # DESIGN: dropping lines with post processing, and echoing a blank line is a 367 | # hack to deal with the PS2 prompt confusing Org evaluation 368 | bash -c " 369 | . \"$NIX_PROFILE/share/direnv-nix-lorelei/nix-lorelei.bash\" 370 | echo; use_nix_gcrooted --help 371 | " 372 | #+end_src 373 | 374 | #+results: help 375 | #+begin_example 376 | USAGE: use_nix_gcrooted [OPTION]... [FILE] 377 | 378 | DESCRIPTION: 379 | 380 | A replacement for Direnv's use_nix. This function, will make 381 | sure calculated Nix expressions are GC rooted with Nix. By 382 | default the calculated environment is also cached, which is 383 | useful for Nix expressions that have costly evaluations. To 384 | invalidate the cache, files can be watched either by their 385 | content hash or their modification time. You can also delete 386 | .direnv/delete_to_rebuild to invalidate the cache. 387 | 388 | OPTIONS: 389 | 390 | -h --help print this help message 391 | -a --auto-watch-content watch autodetected files for contect 392 | changes 393 | -A --auto-watch-mtime watch autodetected files for 394 | modification times 395 | -d --auto-watch-deep deeper searching for -a and -A options 396 | -w --watch-content PATH watch a file's content for changes 397 | -W --watch-mtime PATH watch a file's modification time 398 | -C --ignore-cache recompute new environment every time 399 | -k --keep-last NUM protect last N caches from GC 400 | (default 5) 401 | #+end_example 402 | 403 | Direnv needs to know when to consider recalculating an environment's variables. 404 | To do this, we need to register files to watch for changes. This is what the 405 | "watch" switches above help specify. 406 | 407 | With the =--auto-watch-content= and =--auto-watch-mtime= switches, you don't 408 | have to worry about which files to watch for changes. You can either watch these 409 | files when their modifications time change, or when their content actually 410 | changes (touching a file changes its modification time, but not its content). 411 | 412 | The =--auto-watch-content= and =--auto-watch-mtime= switches catch a good amount 413 | of Nix files, but won't catch everything you might have the idea to watch. If 414 | you want to specify files to watch explicitly, you can use the =--watch-content= 415 | and =--watch-mtime= switches. 416 | 417 | You can use the =--auto-watch-deep= switch to have the auto-watching features 418 | look a little deeper for files to watch. However, the evaluation time you'll 419 | face for an not-yet-cached environment will be notably longer for this deeper 420 | search (possibly twice as long). Note auto-watching without the 421 | =--auto-watch-deep= switch shouldn't add much evaluation overhead, so you should 422 | be able to use the normal shallower auto-detection without worrying about a 423 | slowdown. 424 | 425 | If for some (unlikely) reason, you want the benefits of protection from Nix 426 | garbage collection, but not cache the evaluation of environments, you can use 427 | =--ignore-cache=. Note, that you still need to specify files to watch for 428 | changes. With =--ignore-cache=, you'll recalculate the Nix expression for your 429 | project every time these watched files trigger Direnv to recalculate an 430 | environment. 431 | 432 | Lorelei keeps the last five environments from being garbage collected. You can 433 | change this with =--keep-last=. 434 | 435 | And finally, if you ever feel like you want to dump your cached environment and 436 | recalculate everything, just delete =.direnv/delete_to_rebuild=, which will be 437 | next to your project's =.envrc= file. 438 | 439 | Lorelei's metadata for your project is in two places: 440 | - your project's =.direnv= directory 441 | - your user's GC root directory: =/nix/var/nix/gcroots/per-user/$USER= 442 | 443 | You can delete this data to start fresh. 444 | 445 | The symlinks in the GC root directory have human readable names to assist manual 446 | curation if you need it. 447 | 448 | * Prior art 449 | 450 | There are four projects that were considered before writing Lorelei: 451 | - [[lorri][Lorri]] 452 | - [[sorri][Sorri]] 453 | - [[nixdirenv][Nix-direnv]] 454 | - [[nixify][Nixify]] 455 | 456 | Lorelei should subsume the features of all of these projects with the exception 457 | of Lorri's approach to calculating Direnv environments as a background process. 458 | You can think of the name "Lorelei" as a pun of "Lorri-lite," but "Lorelei" is 459 | also the name of a [[lorelei-song][Pogue's song]] you may enjoy. 460 | 461 | All of these different projects can save on the evaluation time of calculating a 462 | Nix expression by caching the Direnv environment. And all of these projects have 463 | some facility to protect dependencies referenced by Direnv environments from 464 | Nix's garbage collection. 465 | 466 | Lorri is the heaviest of these options. To use it, you start a daemon process 467 | that in the background watches files for changes and evaluates/builds 468 | environments. This way, the environment is ready before you actually enter the 469 | project. 470 | 471 | Also Lorri inspects Nix's build log to automatically detect which files need to 472 | be watched for changes. Unfortunately, this often misses useful files to watch 473 | in a project. 474 | 475 | Running a background process can be a heavy extra process, and introduces the 476 | surface area of complexity and exposure to defects (though the Lorri committers 477 | have been committed to fixing them). All of the other projects are 478 | lighter-weight than Lorri in this regard. They are just scripts with no 479 | requirements on a background process. 480 | 481 | Sorri copies a lot of code from Lorri, but removes the background process. So 482 | when you enter a Direnv directory, you will always experience the evaluation 483 | time of calculating a not-yet-cached Direnv environment. With Lorri this 484 | evaluation occurs in the background. 485 | 486 | Lorelei is different from Sorri in two main ways: 487 | 488 | - Lorelei gives much more control of cache invalidation beyond the 489 | auto-detection of files to watch for changes. These approaches are inspired by 490 | Nix-direnv and Nixify. 491 | 492 | - Rather than copying code from Lorri, we actually call Lorri code directly as a 493 | library. 494 | 495 | Lorri has been relatively active about refining the approach to calculating a 496 | Direnv environment, more so than any of the other projects. Sorri copies code, 497 | but leads to more work porting changes from Lorri to Sorri. Lorelei uses Nix to 498 | use Lorri's code directly. This eases maintenance, but does mean that you /have/ 499 | to install Lorelei with Nix. However, this is not a bad idea, because Lorelei 500 | rigorously pins all of its dependencies, all the way down to =coreutils=. So by 501 | installing Lorelei with Nix, we get more precision. 502 | 503 | * Known limitations 504 | 505 | There's two known limitations of Lorelei: 506 | - Your project must have a Nix file that can be run with =nix-shell=. 507 | - Nix flakes aren't supported (yet). 508 | 509 | Lorelei delegates strongly to Lorri, so the limitation of requiring an explicit 510 | Nix file to import stems from that. This is not to say that this limitation 511 | can't be improved upon in the future. 512 | 513 | However, we probably don't want to support something like =nix-shell='s 514 | =--packages= switch. This feature of =nix-shell= is generally discouraged by the 515 | Nix community because its implementation has a lot of non-intuitive warts. Nix 516 | will soon release a =nix shell= command that has the potential to more properly 517 | replace the functionality that =nix-shell='s =--packages= switch provides. When 518 | this occurs, both the Lorri and Lorelei can reevaluate their respective 519 | implementation strategies. 520 | 521 | Also, soon to be released in a new version of Nix are [[nix-flakes][Nix flakes]]. If you don't 522 | know what flakes are, you may want to wait until they stabilize and are 523 | officially released. If you're an early adopter of flakes, the [[nixdirenv][Nix-direnv]] 524 | project has support for Nix flakes with it's =use_flake= function. Lorelei can 525 | be installed and used concurrently with other projects offering similar 526 | functionality (Lorri, Nix-direnv, and the rest). You just make different calls 527 | in your project's =.envrc= files. No core contributor of Lorelei is using this 528 | unreleased version of Nix supporting flakes, so we didn't want to provide 529 | something we had not tested ourselves. 530 | 531 | * Release 532 | 533 | The "main" branch of the repository on GitHub has the latest released version 534 | of this code. There is currently no commitment to either forward or backward 535 | compatibility. 536 | 537 | "user/shajra" branches are personal branches that may be force-pushed to. The 538 | "main" branch should not experience force-pushes and is recommended for 539 | general use. 540 | 541 | * License 542 | 543 | All files in this "direnv-nix-lorelei" project are licensed under the terms of 544 | GPLv3 or (at your option) any later version. 545 | 546 | Please see the [[./COPYING.md][./COPYING.md]] file for more details. 547 | 548 | * Contribution 549 | 550 | Feel free to file issues and submit pull requests with GitHub. 551 | 552 | There is only one author to date, so the following copyright covers all files in 553 | this project: 554 | 555 | Copyright © 2020 Sukant Hajra 556 | 557 | * Org-mode teardown :noexport: 558 | 559 | #+call: cleanup() 560 | -------------------------------------------------------------------------------- /default.nix: -------------------------------------------------------------------------------- 1 | (import ./nix {}).distribution 2 | -------------------------------------------------------------------------------- /doc/links.org: -------------------------------------------------------------------------------- 1 | #+link: cachix https://cachix.org 2 | #+link: direnv https://direnv.net 3 | #+link: direnv-docs https://direnv.net/#docs 4 | #+link: direnv-editor https://github.com/direnv/direnv/wiki#editor-integration 5 | #+link: direnv-shell https://direnv.net/docs/hook.html 6 | #+link: github-actions https://github.com/shajra/direnv-nix-lorelei/actions 7 | #+link: homemanager https://github.com/nix-community/home-manager 8 | #+link: homemanager-manual https://rycee.gitlab.io/home-manager/ 9 | #+link: lorelei-song https://www.youtube.com/watch?v=VDw81PRP2SQ 10 | #+link: lorri https://github.com/target/lorri 11 | #+link: niv https://github.com/nmattia/niv 12 | #+link: nix https://nixos.org/nix 13 | #+link: nix-darwin https://daiderd.com/nix-darwin 14 | #+link: nixdirenv https://github.com/nix-community/nix-direnv 15 | #+link: nix-env https://nixos.org/nix/manual/#sec-nix-env 16 | #+link: nix-expr https://nixos.org/nix/manual/#ch-expression-language 17 | #+link: nix-flakes https://nixos.wiki/wiki/Flakes 18 | #+link: nixify https://github.com/kalbasit/nur-packages/blob/master/pkgs/nixify/envrc 19 | #+link: nix-install https://nixos.org/nix/manual/#chap-installation 20 | #+link: nix-learn https://nixos.org/learn.html 21 | #+link: nixos https://nixos.org 22 | #+link: nixpkgs https://github.com/NixOS/nixpkgs 23 | #+link: nixpkgs-manual https://nixos.org/nixpkgs/manual 24 | #+link: nix-tutorial https://github.com/shajra/example-nix/tree/master/tutorials/0-nix-intro 25 | #+link: shajra-provisioning-base https://github.com/shajra/shajra-provisioning/blob/master/home/modules/base/default.nix 26 | #+link: sorri https://github.com/nmattia/sorri 27 | -------------------------------------------------------------------------------- /doc/nix.mac.org: -------------------------------------------------------------------------------- 1 | * About this file 2 | 3 | Though =nix.org= is copied across all my Nix projects, not all of the projects 4 | support MacOS. So this file has any snippets that reference Macs, which can then 5 | be commented out as necessary. 6 | 7 | * Mac installation 8 | 9 | If you're on a recent release of MacOS, you will need an extra switch: 10 | 11 | #+begin_src bash :eval no 12 | sh <(curl -L https://nixos.org/nix/install) --daemon \ 13 | --darwin-use-unencrypted-nix-store-volume 14 | #+end_src 15 | -------------------------------------------------------------------------------- /doc/nix.md: -------------------------------------------------------------------------------- 1 | - [About this document](#sec-1) 2 | - [How this project uses Nix](#sec-2) 3 | - [Motivation to use Nix](#sec-3) 4 | - [Level of commitment/risk](#sec-4) 5 | - [Installation and setup](#sec-5) 6 | - [Nix package manager setup](#sec-5-1) 7 | - [Cache setup](#sec-5-2) 8 | - [Working with Nix](#sec-6) 9 | - [Searching Nix files](#sec-6-1) 10 | - [Building Nix expressions](#sec-6-2) 11 | - [Running commands](#sec-6-3) 12 | - [Installing and uninstalling programs](#sec-6-4) 13 | - [Garbage collection](#sec-6-5) 14 | - [Understanding derivations](#nix-drv) 15 | - [Lazy evaluation](#sec-6-7) 16 | - [Next steps](#sec-7) 17 | 18 | 19 | # About this document 20 | 21 | This document is included for people somewhat new to Nix. Although the [official Nix documentation](https://nixos.org/learn.html) has gotten substantially better with time, this is an embedded guide to help get started with Nix so it's easier to use the rest of the project. 22 | 23 | Note that this document only covers the Nix package manager, not [NixOS](https://nixos.org) (a full Linux operating system built on top of Nix) or [Nix-Darwin](https://daiderd.com/nix-darwin) (a project that gives the benefits of NixOS for MacOS). 24 | 25 | # How this project uses Nix 26 | 27 | This project uses the [Nix package manager](https://nixos.org/nix) to download all necessary dependencies and build everything from source. In this regard, Nix is helpful as not just a package manager, but also a build tool. Nix helps us get from raw source files to not only built executables, but all the way to a Nix package, which we can install with Nix if we like. 28 | 29 | [This project's continuous integration (using GitHub Actions)](https://github.com/shajra/direnv-nix-lorelei/actions) caches built packages at [Cachix](https://cachix.org), a service for caching pre-built Nix packages. If you don't want to wait for a full local build when first using this project, setting up Nix to pull from Cachix is recommended. 30 | 31 | Within this project, the various files with a ".nix" extension are Nix files, each of which contains an expression written in the [Nix expression language](https://nixos.org/nix/manual/#ch-expression-language) used by the Nix package manager to specify packages. If you get proficient with this language, you can use these expressions as a starting point to compose your own packages beyond what's provided in this project. 32 | 33 | # Motivation to use Nix 34 | 35 | When making a new software project, wrangling dependencies can be a chore. For instance, GNU Make's makefiles often depend on executables and libraries that may not yet be available on a system. The makefiles in most projects don't assist with getting these dependencies at usable versions. And when projects document how to get and install dependencies, there can be a lot of room for error. 36 | 37 | Nix can build and install projects in a way that's precise, repeatable, and guaranteed not to conflict with anything already installed. Every single dependency needed to build a package is specified in Nix expressions. For each dependency needed to build a package, Nix will download the dependency, build it, and install it as a Nix package for use as a dependency. Nix can even concurrently install multiple versions of any dependency without conflicts. 38 | 39 | Every dependency of a Nix package is itself a Nix package. And Nix supports building packages for a variety of languages. Nix picks up where language-specific tooling stops, layering on top of the tools and techniques native to those ecosystems. Since each package is specified by a Nix expression, and because Nix expressions are designed to be composed together to make new ones, we can make our own expressions to specify new packages with dependencies that may not all come from the same language ecosystem. 40 | 41 | To underscore how repeatable and precise Nix builds are, it helps to know that Nix uniquely identifies packages by a hash derived from the hashes of requisite dependencies and configuration. This is a recursive hash calculation that assures that the smallest change to even a distant transitive dependency of a package changes its hash. When dependencies are downloaded, they are checked against the expected hash. Most Nix projects (this one included) are careful to pin dependencies to specific versions/hashes. Because of this, when building the same project with Nix on two different systems, we get an extremely high confidence we will get the same output, often bit-for-bit. This is a profound degree of precision relative to other popular package managers. 42 | 43 | The repeatability and precision of Nix enables caching services, which for Nix are called *substitutors*. Cachix is one such substitutor. Before building a package, the hash for the package is calculated. If any configured substitutor has a build for the hash, it's pulled down as a substitute. A certificate-based protocol is used to establish trust of substitutors. Between this protocol, and the algorithm for calculating hashes in Nix, you can have confidence that a package pulled from a substitutor will be identical to what you would have built locally. 44 | 45 | All of this makes Nix an attractive tool for managing almost any software project. 46 | 47 | # Level of commitment/risk 48 | 49 | Unless you're on NixOS, you're likely already using another package manager for your operating system already (APT, Yum, etc.). You don't have to worry about Nix or packages installed by Nix conflicting with anything already on your system. Running Nix along side other package managers is safe. 50 | 51 | All the files of a Nix package are located under `/nix` a directory, well isolated from any other package manager. Nix won't touch any directories like `/etc` or `/usr/local`. Nix then symlinks files under `/nix` to your home directory under dot-files like `~/.nix-profile`. 52 | 53 | Hopefully, this alleviates any worry about installing a complex program on your machine. Uninstallation is nearly as easy as deleting everything under `/nix`. 54 | 55 | # Installation and setup 56 | 57 | ## Nix package manager setup 58 | 59 | > **NOTE:** You don't need this step if you're running NixOS, which comes with Nix baked in. 60 | 61 | If you don't already have Nix, [the official installation script](https://nixos.org/learn.html) should work on a variety of UNIX-like operating systems: 62 | 63 | ```bash 64 | sh <(curl -L https://nixos.org/nix/install) --daemon 65 | ``` 66 | 67 | If you're on a recent release of MacOS, you will need an extra switch: 68 | 69 | ```bash 70 | sh <(curl -L https://nixos.org/nix/install) --daemon \ 71 | --darwin-use-unencrypted-nix-store-volume 72 | ``` 73 | 74 | After installation, you may have to exit your terminal session and log back in to have environment variables configured to put Nix executables on your `PATH`. 75 | 76 | The `--daemon` switch installs Nix in the recommended multi-user mode. This requires the script to run commands with `sudo`. The script fairly verbosely reports everything it does and touches. If you later want to uninstall Nix, you can run the installation script again, and it will tell you what to do to get back to a clean state. 77 | 78 | The Nix manual describes [other methods of installing Nix](https://nixos.org/nix/manual/#chap-installation) that may suit you more. 79 | 80 | ## Cache setup 81 | 82 | It's recommended to configure Nix to use shajra.cachix.org as a Nix *substitutor*. This project pushes built Nix packages to [Cachix](https://cachix.org) as part of its continuous integration. Once configured, Nix will pull down these pre-built packages instead of building them locally (potentially saving a lot of time). This augments the default substitutor that pulls from cache.nixos.org. 83 | 84 | You can configure shajra.cachix.org as a substitutor with the following command: 85 | 86 | ```sh 87 | nix run \ 88 | --file https://cachix.org/api/v1/install \ 89 | cachix \ 90 | --command cachix use shajra 91 | ``` 92 | 93 | Cachix is a service that anyone can use. You can call this command later to add substitutors for someone else using Cachix, replacing "shajra" with their cache's name. 94 | 95 | If you've just run a multi-user Nix installation and are not yet a trusted user in `/etc/nix/nix.conf`, this command may not work. But it will report back some options to proceed. 96 | 97 | One option sets you up as a trusted user, and installs Cachix configuration for Nix locally at `~/.config/nix/nix.conf`. This configuration will be available immediately, and any subsequent invocation of Nix commands will take advantage of the Cachix cache. 98 | 99 | You can alternatively configure Cachix as a substitutor globally by running the above command as a root user (say with `sudo`), which sets up Cachix directly in `/etc/nix/nix.conf`. The invocation may give further instructions upon completion. 100 | 101 | # Working with Nix 102 | 103 | Though covering Nix comprehensively is beyond the scope of this document, we'll go over a few commands illustrating some usage of Nix with this project. 104 | 105 | ## Searching Nix files 106 | 107 | Each of the Nix files in this project (files with a ".nix" extension) contains exactly one Nix expression. This expression evaluates to one of the following values: 108 | 109 | - simple primitives and functions 110 | - *derivations* of packages that can be built and installed with Nix 111 | - containers of values, allowing a single value to provide multiple values of different types, including more containers of values. 112 | 113 | Once you learn the Nix language, you can read these files to see what kind of values they build. We can use the `nix search` command to see what package derivations a Nix expression contains. For example from the root directory of this project, we can execute: 114 | 115 | ```sh 116 | nix search --file default.nix --no-cache 117 | ``` 118 | 119 | * direnv (direnv) 120 | A shell extension that manages your environment 121 | 122 | * direnv-nix-lorelei (direnv-nix-lorelei) 123 | Alternative Nix functions for Direnv 124 | 125 | If you don't get the results above, see the [section on understanding derivations](#nix-drv) for an explanation of a likely problem and workaround. 126 | 127 | Note that because for extremely large Nix expressions, searching can be slow, `nix search` by default returns results from searching an indexed cache. This cache is updated explicitly (with an `--update-cache` switch) but may be inconsistent with what you really want to search. It can be confusing to get incorrect results due to an inconsistent cache. However, because small local projects rarely have that many package derivations we don't really need the cache, and can bypass it with the `--no-cache` switch, as used above. This guarantees accurate results that are fast enough. So for the purposes of this project, it's recommended to always use `--no-cache`. 128 | 129 | The output of `nix search` is formatted as 130 | 131 | * attribute-path (name-of-package) 132 | Short description of package 133 | 134 | *Attribute paths* are used to select values from Nix sets that might be nested. A dot delimits *attributes* in the path. For instance an attribute path of `a.b` selects a value from a set with an `a` attribute that has set with a `b` attribute, that then has the value to select. 135 | 136 | If the Nix expression we're searching evaluates to a single derivation (not in a container), the attribute path will be missing from the `nix search` result. 137 | 138 | Many Nix commands evaluate Nix files. If you specify a directory instead, the command will look for a `default.nix` file within to evaluate. So from the root directory of this project, we could use `.` instead of `default.nix`: 139 | 140 | ```sh 141 | nix search --file . --no-cache 142 | ``` 143 | 144 | In the remainder of this document, we'll use `.` instead of `default.nix` since this is conventional for Nix. 145 | 146 | ## Building Nix expressions 147 | 148 | The following result is one returned by our prior execution of `nix search --no-cache --file .`: 149 | 150 | * direnv-nix-lorelei (direnv-nix-lorelei) 151 | Alternative Nix functions for Direnv 152 | 153 | We can see that a package named "direnv-nix-lorelei" can be accessed with the `direnv-nix-lorelei` attribute path in the Nix expression in the project root's `default.nix`. Not shown in the search results above, this package happens to provide the library `nix-alt.sh`. 154 | 155 | We can build this package with `nix build` from the project root: 156 | 157 | ```sh 158 | nix build --file . direnv-nix-lorelei 159 | ``` 160 | 161 | The positional arguments to `nix build` are *installables*, which can be referenced by attribute paths. If you supply none then all derivations found are built by default. 162 | 163 | All packages built by Nix are stored in `/nix/store`. Nix won't rebuild packages found there. Once a package is built, its content in `/nix/store` is read-only (until the package is garbage collected, discussed later). 164 | 165 | After a successful call of `nix build`, you'll see one or more symlinks for each package requested in the current working directory. These symlinks by default have a name prefixed with "result" and point back to the respective build in `/nix/store`: 166 | 167 | ```sh 168 | readlink result* 169 | ``` 170 | 171 | /nix/store/q44il55npbs3pj2zpg0f828hy6miysn0-direnv-nix-lorelei 172 | 173 | Following these symlinks, we can see the files the project provides: 174 | 175 | ```sh 176 | tree -l result* 177 | ``` 178 | 179 | result 180 | └── share 181 | └── direnv-nix-lorelei 182 | └── nix-lorelei.bash 183 | 184 | 2 directories, 1 file 185 | 186 | It's common to configure these "result" symlinks as ignored in source control tools (for instance, for Git within a `.gitignore` file). 187 | 188 | `nix build` has a `--no-link` switch in case you want to build packages without creating "result" symlinks. To get the paths where your packages are located, you can use `nix path-info` after a successful build: 189 | 190 | ```sh 191 | nix path-info --file . direnv-nix-lorelei 192 | ``` 193 | 194 | /nix/store/q44il55npbs3pj2zpg0f828hy6miysn0-direnv-nix-lorelei 195 | 196 | ## Running commands 197 | 198 | We can run commands in Nix-curated environments with `nix run`. Nix will take executables found in packages, put them in an environment's `PATH`, and then execute a user-specified command. 199 | 200 | With `nix run`, you don't even have to build the package first with `nix build` or mess around with "result" symlinks. `nix run` will build the project if it's not yet been built. 201 | 202 | For example, to get the help message for the `direnv` executable provided by the `direnv` package selected by the `direnv` attribute path from `.`, we can call the following: 203 | 204 | ```sh 205 | nix run \ 206 | --file . \ 207 | direnv \ 208 | --command direnv --help 209 | ``` 210 | 211 | direnv v2.28.0 212 | Usage: direnv COMMAND [...ARGS] 213 | 214 | Available commands 215 | ------------------ 216 | … 217 | 218 | Thus far, the argument of the `--file` switch has always referenced a Nix file on our local filesystem. However, it's possible to reference a Nix expression downloaded from the internet. The Nix ecosystem is supported by a giant GitHub repository of Nix expressions called [Nixpkgs](https://github.com/NixOS/nixpkgs). Special branches of this repository are considered *channels* in the Nix ecosystem. A Nixpkgs branch of "nixos-21.05" can be referenced by "channel:nixos-21.05" for `nix` subcommands that accept a `--file` switch. 219 | 220 | Again, as with `nix build`, attribute paths are specified as positional arguments to select packages. 221 | 222 | The command to run is specified after the `--command` switch. `nix run` runs the command in a shell set up with a `PATH` environment variable including all the `bin` directories provided by the selected packages. 223 | 224 | `nix run` also supports an `--ignore-environment` flag that restricts `PATH` to only packages selected, rather than extending the `PATH` of the caller's environment. With `--ignore-environment`, the invocation is more sandboxed. 225 | 226 | ## Installing and uninstalling programs 227 | 228 | We've seen that we can build programs with `nix build` and then execute them using the "result" symlink (`result/bin/*`). Additionally, we've seen that you can run programs with `nix run`. But these additional steps and switches/arguments can feel extraneous. It would be nice if we could just have the programs on our `PATH`. This is what `nix-env` is for. 229 | 230 | `nix-env` maintains a symlink tree, called a *profile*, of installed programs. The active profile is pointed to by a symlink at `~/.nix-profile`. By default, this profile points to `/nix/var/nix/profiles/per-user/$USER/profile`. But you can point your `~/.nix-profile` to any writable location with the `--switch-profile` switch: 231 | 232 | ```sh 233 | nix-env --switch-profile /nix/var/nix/profiles/per-user/$USER/another-profile 234 | ``` 235 | 236 | This way, you can just put `~/.nix-profile/bin` on your `PATH`, and any programs installed in your currently active profile will be available for interactive use or scripts. 237 | 238 | We can query what's installed in the active profile with the `--query` switch: 239 | 240 | ```sh 241 | nix-env --query 242 | ``` 243 | 244 | To install the `nix-alt.sh` library, which is accessed by the `direnv-nix-lorelei` in our top-level `default.nix` file, we'd run the following: 245 | 246 | ```sh 247 | nix-env --install --file . --attr direnv-nix-lorelei 2>&1 248 | ``` 249 | 250 | installing 'direnv-nix-lorelei' 251 | 252 | We can see this installation by querying what's been installed: 253 | 254 | ```sh 255 | nix-env --query 256 | ``` 257 | 258 | direnv-nix-lorelei 259 | 260 | And if we want to uninstall a program from our active profile, we do so by its name, in this case "direnv-nix-lorelei": 261 | 262 | ```sh 263 | nix-env --uninstall direnv-nix-lorelei 2>&1 264 | ``` 265 | 266 | uninstalling 'direnv-nix-lorelei' 267 | 268 | Note that we've installed our package using its attribute path (`direnv-nix-lorelei`) within the referenced Nix expression. But we uninstall it using the package name ("direnv-nix-lorelei"), which may or may not be the same as the attribute path. When a package is installed, Nix keeps no reference to the expression that evaluated to the derivation of the installed package. The attribute path is only relevant to this expression. In fact, two different expressions could evaluate to the same derivation, but use different attribute paths. This is why we uninstall packages by their package name. 269 | 270 | Also, if you look at the location for your profile, you'll see that Nix retains the symlink trees of previous generations of your profile. In fact you can even rollback to a previous profile with the `--rollback` switch. You can delete old generations of your profile with the `--delete-generations` switch. 271 | 272 | See the [documentation for `nix-env`](https://nixos.org/nix/manual/#sec-nix-env) for more details. 273 | 274 | ## Garbage collection 275 | 276 | Every time you build a new version of your code, it's stored in `/nix/store`. There is a command called `nix-collect-garbage` that purges unneeded packages. Programs that should not be removed by `nix-collect-garbage` can by found by starting with symlinks stored as *garbage collection (GC) roots* under three locations: 277 | 278 | - `/nix/var/nix/gcroots` 279 | - `/nix/var/nix/profiles` 280 | - `/nix/var/nix/manifests`. 281 | 282 | For each package, Nix is aware of all references back to other packages in `/nix/store`, whether in text files or binaries. This helps Nix assure that dependencies of packages linked as GC roots won't be deleted. 283 | 284 | Each "result" symlink created by a `nix build` invocation has a symlink in `/nix/var/nix/gcroots/auto` pointing back it. So we've got symlinks in `/nix/var/nix/gcroots/auto` pointing to "result" symlinks in our projects, which then reference the actual built project in `/nix/store`. These chains of symlinks prevent packages built by `nix build` from being garbage collected. 285 | 286 | If you want a package you've built with `nix build` to be garbage collected, delete the "result" symlink created before calling `nix-collect-garbage`. Breaking symlink chains under `/nix/var/nix/gcroots` removes protection from garbage collection. `nix-collect-garbage` will clean up broken symlinks when it runs. 287 | 288 | Note that everything under `/nix/var/nix/profiles` is considered a GC root as well. This is why users by convention use this location to store their `nix-env` profiles. 289 | 290 | Also, note if you delete a “result\*” link and call `nix-collect-garbage`, though some garbage may be reclaimed, you may find that an old `nix-env` profile is keeping the program alive. As a convenience, `nix-collect-garbage` has a `--delete-old` switch that will delete these old profiles (it just calls `nix-env --delete-generations` on your behalf). 291 | 292 | It's also good to know that `nix-collect-garbage` won't delete packages referenced by any running processes. In the case of `nix run` no garbage collection root symlink is created under `/nix/var/nix/gcroots`, but while `nix run` is running `nix-collect-garbage` won't delete packages needed by the running command. However, once the `nix run` call exits, any packages pulled from a substitutor or built locally are candidates for deletion by `nix-collect-garbage`. If you called `nix run` again after garbage collecting, those packages may be pulled or built again. 293 | 294 | ## Understanding derivations 295 | 296 | We haven't detailed what happens when we build a Nix expression that evaluates to a package derivation. There are two important steps: 297 | 298 | 1. *instantiating* the derivation 299 | 2. *realizing* the instantiated derivation, which builds the final package. 300 | 301 | An instantiated derivation is effectively a script stored in `/nix/store` that Nix can run to build the final package (which also ends up in `/nix/store`). These instantiated derivations have a ".drv" extension, and if you look in `/nix/store` you may find some. Instantiated derivations have references to all necessary build dependencies, also in `/nix/store`, which means that everything is physically in place in `/nix/store` to build the package (no network connectivity is needed to realize an instantiated derivation). 302 | 303 | Note that both `nix build` and `nix run` perform both instantiation and realization of a derivation, so for the most part, we don't have to worry about the difference between instantiating and realizing a derivation. 304 | 305 | However, you may encounter a Nix expression where `nix search` returns nothing, though you're sure that there are derivations to select out. In this case, the Nix expression is using an advanced technique that unfortunately hides attributes from `nix search` until some derivations are instantiated into `/nix/store`. We can force the instantiation of these derivations without realizing their packages with the following command: 306 | 307 | ```sh 308 | nix show-derivation --file default.nix 309 | ``` 310 | 311 | Once these derivations are instantiated, you may get more results with `nix search` for the occasional Nix expression that uses some advanced techniques. 312 | 313 | ## Lazy evaluation 314 | 315 | We haven't made a big deal of it, but the Nix language is *lazily evaluated*. This allows a single Nix expression to refer to several thousand packages, but without requiring us to evaluate everything when selecting out packages by attribute paths. In fact, the entire NixOS operating system is based heavily on a single single expression managed in a Git repository called [Nixpkgs](https://github.com/NixOS/nixpkgs). 316 | 317 | # Next steps 318 | 319 | This document has covered a fraction of Nix usage, hopefully enough to introduce Nix in the context of [this project](../README.md). 320 | 321 | An obvious place to start learning more about Nix is [the official documentation](https://nixos.org/learn.html). The author of this project also maintains another project with [a small tutorial on Nix](https://github.com/shajra/example-nix/tree/master/tutorials/0-nix-intro). This tutorial covers the Nix expression language in more detail. 322 | 323 | All the commands we've covered have more switches and options. See the respective man pages for more. Also, we didn't cover `nix-shell`, which can be used for setting up development environments. And we didn't cover much of [Nixpkgs](https://github.com/NixOS/nixpkgs), the gigantic repository of community-curated Nix expressions. 324 | 325 | The Nix ecosystem is vast. This project and documentation illustrates just a small sample of what Nix can do. 326 | -------------------------------------------------------------------------------- /doc/nix.org: -------------------------------------------------------------------------------- 1 | #+title: Nix Setup and Usage 2 | #+setupfile: links.org 3 | 4 | * Org-mode setup :noexport: 5 | 6 | This document is written in a project-agnostic way so it can be copied to other 7 | projects that use Nix. 8 | 9 | ** Variables 10 | 11 | We set variables in =nix.org.el= and access those settings with the following 12 | macros and source code blocks (using Noweb). 13 | 14 | #+name: get 15 | #+begin_src emacs-lisp :var arg="" :eval yes :results silent 16 | (alist-get (intern arg) (car (read-from-string (f-read "nix.org.el")))) 17 | #+end_src 18 | 19 | #+macro: get (eval (concat $2 (alist-get (intern $1) (car (read-from-string (f-read "nix.org.el")))) $2)) 20 | #+macro: package-attr {{{get(package-attr,=)}}} 21 | #+macro: package-name {{{get(package-name,")}}} 22 | #+macro: package-type {{{get(package-type)}}} 23 | #+macro: package-target {{{get(package-target,=)}}} 24 | #+macro: run-src {{{get(run-src,=)}}} 25 | #+macro: run-attr {{{get(run-attr,=)}}} 26 | #+macro: run-name {{{get(run-name,=)}}} 27 | #+macro: run-target {{{get(run-target,=)}}} 28 | #+macro: nixos-release {{{get(nixos-release)}}} 29 | 30 | ** Formatting help 31 | 32 | This snippet can be used as a post-processing step to crop down the results from 33 | an evaluation of a source code block. 34 | 35 | #+name: crop 36 | #+begin_src emacs-lisp :var text="" :var first-n=5 :var last-n=5 :results silent 37 | (let* ((ls (split-string text "\n")) 38 | (first-ls (-take first-n ls)) 39 | (rest-first (-drop first-n ls)) 40 | (rest-last (-drop-last (+ 1 last-n) rest-first)) 41 | (last-ls (-take-last (+ 1 last-n) rest-first))) 42 | (string-join 43 | (if rest-last 44 | (append first-ls '("…") last-ls) 45 | (append first-ls last-ls)) 46 | "\n")) 47 | #+end_src 48 | 49 | ** Setup action 50 | 51 | The following helps (using Noweb) set up Nix environment variables for source 52 | block evaluation. 53 | 54 | #+name: nix-init 55 | #+begin_src sh :eval no 56 | export NIX_PROFILE=$(pwd)/nix-profile 57 | export NIX_PAGER=cat 58 | export PATH="$NIX_PROFILE/bin:$PATH" 59 | #+end_src 60 | 61 | Next we perform some side-effects to set up the evaluation of the whole 62 | document. 63 | 64 | #+name: cleanup 65 | #+begin_src sh :dir .. :results output silent :noweb yes 66 | <> 67 | rm --force result* 68 | rm --force "$NIX_PROFILE"* 69 | #+end_src 70 | 71 | This is just a hack to deal with the fact that we never know what directory a 72 | session will start in, so we need a way to calculate the PWD to jump to it. 73 | 74 | #+name: pwd-parent 75 | #+begin_src sh :results output silent 76 | echo cd "$(pwd)/.." 77 | #+end_src 78 | 79 | This begins a session with environment variables initialized. 80 | 81 | #+name: session-init 82 | #+begin_src sh :session env :results output silent :noweb yes 83 | <> 84 | <> 85 | #+end_src 86 | 87 | * About this document 88 | 89 | This document is included for people somewhat new to Nix. Although the [[nix-learn][official 90 | Nix documentation]] has gotten substantially better with time, this is an embedded 91 | guide to help get started with Nix so it's easier to use the rest of the 92 | project. 93 | 94 | Note that this document only covers the Nix package manager, not [[nixos][NixOS]] (a full 95 | Linux operating system built on top of Nix) or [[nix-darwin][Nix-Darwin]] (a project that gives 96 | the benefits of NixOS for MacOS). 97 | 98 | * How this project uses Nix 99 | 100 | This project uses the [[nix][Nix package manager]] to download all necessary dependencies 101 | and build everything from source. In this regard, Nix is helpful as not just a 102 | package manager, but also a build tool. Nix helps us get from raw source files 103 | to not only built executables, but all the way to a Nix package, which we can 104 | install with Nix if we like. 105 | 106 | [[github-actions][This project's continuous integration (using GitHub Actions)]] caches built 107 | packages at [[cachix][Cachix]], a service for caching pre-built Nix packages. If you don't 108 | want to wait for a full local build when first using this project, setting up 109 | Nix to pull from Cachix is recommended. 110 | 111 | Within this project, the various files with a ".nix" extension are Nix files, 112 | each of which contains an expression written in the [[nix-expr][Nix expression language]] used 113 | by the Nix package manager to specify packages. If you get proficient with this 114 | language, you can use these expressions as a starting point to compose your own 115 | packages beyond what's provided in this project. 116 | 117 | * Motivation to use Nix 118 | 119 | When making a new software project, wrangling dependencies can be a chore. For 120 | instance, GNU Make's makefiles often depend on executables and libraries that 121 | may not yet be available on a system. The makefiles in most projects don't 122 | assist with getting these dependencies at usable versions. And when projects 123 | document how to get and install dependencies, there can be a lot of room for 124 | error. 125 | 126 | Nix can build and install projects in a way that's precise, repeatable, and 127 | guaranteed not to conflict with anything already installed. Every single 128 | dependency needed to build a package is specified in Nix expressions. For each 129 | dependency needed to build a package, Nix will download the dependency, build 130 | it, and install it as a Nix package for use as a dependency. Nix can even 131 | concurrently install multiple versions of any dependency without conflicts. 132 | 133 | Every dependency of a Nix package is itself a Nix package. And Nix supports 134 | building packages for a variety of languages. Nix picks up where 135 | language-specific tooling stops, layering on top of the tools and techniques 136 | native to those ecosystems. Since each package is specified by a Nix expression, 137 | and because Nix expressions are designed to be composed together to make new 138 | ones, we can make our own expressions to specify new packages with dependencies 139 | that may not all come from the same language ecosystem. 140 | 141 | To underscore how repeatable and precise Nix builds are, it helps to know that 142 | Nix uniquely identifies packages by a hash derived from the hashes of requisite 143 | dependencies and configuration. This is a recursive hash calculation that 144 | assures that the smallest change to even a distant transitive dependency of a 145 | package changes its hash. When dependencies are downloaded, they are checked 146 | against the expected hash. Most Nix projects (this one included) are careful to 147 | pin dependencies to specific versions/hashes. Because of this, when building the 148 | same project with Nix on two different systems, we get an extremely high 149 | confidence we will get the same output, often bit-for-bit. This is a profound 150 | degree of precision relative to other popular package managers. 151 | 152 | The repeatability and precision of Nix enables caching services, which for Nix 153 | are called /substitutors/. Cachix is one such substitutor. Before building a 154 | package, the hash for the package is calculated. If any configured substitutor 155 | has a build for the hash, it's pulled down as a substitute. A certificate-based 156 | protocol is used to establish trust of substitutors. Between this protocol, and 157 | the algorithm for calculating hashes in Nix, you can have confidence that a 158 | package pulled from a substitutor will be identical to what you would have built 159 | locally. 160 | 161 | All of this makes Nix an attractive tool for managing almost any software 162 | project. 163 | 164 | * Level of commitment/risk 165 | 166 | Unless you're on NixOS, you're likely already using another package manager for 167 | your operating system already (APT, Yum, etc.). You don't have to worry about 168 | Nix or packages installed by Nix conflicting with anything already on your 169 | system. Running Nix along side other package managers is safe. 170 | 171 | All the files of a Nix package are located under =/nix= a directory, well 172 | isolated from any other package manager. Nix won't touch any directories like 173 | =/etc= or =/usr/local=. Nix then symlinks files under =/nix= to your home 174 | directory under dot-files like =~/.nix-profile=. 175 | 176 | Hopefully, this alleviates any worry about installing a complex program on your 177 | machine. Uninstallation is nearly as easy as deleting everything under =/nix=. 178 | 179 | * Installation and setup 180 | 181 | ** Nix package manager setup 182 | 183 | #+begin_quote 184 | *_NOTE:_* You don't need this step if you're running NixOS, which comes with Nix 185 | baked in. 186 | #+end_quote 187 | 188 | If you don't already have Nix, [[nix-learn][the official installation script]] should work on a 189 | variety of UNIX-like operating systems: 190 | 191 | #+begin_src bash :eval no 192 | sh <(curl -L https://nixos.org/nix/install) --daemon 193 | #+end_src 194 | 195 | #+include: "nix.mac.org::*Mac installation" :only-contents t 196 | 197 | After installation, you may have to exit your terminal session and log back in 198 | to have environment variables configured to put Nix executables on your =PATH=. 199 | 200 | The =--daemon= switch installs Nix in the recommended multi-user mode. This 201 | requires the script to run commands with =sudo=. The script fairly verbosely 202 | reports everything it does and touches. If you later want to uninstall Nix, you 203 | can run the installation script again, and it will tell you what to do to get 204 | back to a clean state. 205 | 206 | The Nix manual describes [[nix-install][other methods of installing Nix]] that may suit you more. 207 | 208 | ** Cache setup 209 | 210 | It's recommended to configure Nix to use shajra.cachix.org as a Nix 211 | /substitutor/. This project pushes built Nix packages to [[cachix][Cachix]] as part of its 212 | continuous integration. Once configured, Nix will pull down these pre-built 213 | packages instead of building them locally (potentially saving a lot of time). 214 | This augments the default substitutor that pulls from cache.nixos.org. 215 | 216 | You can configure shajra.cachix.org as a substitutor with the following command: 217 | 218 | #+begin_src sh :eval no 219 | nix run \ 220 | --file https://cachix.org/api/v1/install \ 221 | cachix \ 222 | --command cachix use shajra 223 | #+end_src 224 | 225 | Cachix is a service that anyone can use. You can call this command later to add 226 | substitutors for someone else using Cachix, replacing "shajra" with their 227 | cache's name. 228 | 229 | If you've just run a multi-user Nix installation and are not yet a trusted user 230 | in =/etc/nix/nix.conf=, this command may not work. But it will report back some 231 | options to proceed. 232 | 233 | One option sets you up as a trusted user, and installs Cachix configuration for 234 | Nix locally at =~/.config/nix/nix.conf=. This configuration will be available 235 | immediately, and any subsequent invocation of Nix commands will take advantage 236 | of the Cachix cache. 237 | 238 | You can alternatively configure Cachix as a substitutor globally by running the 239 | above command as a root user (say with =sudo=), which sets up Cachix directly in 240 | =/etc/nix/nix.conf=. The invocation may give further instructions upon 241 | completion. 242 | 243 | * Working with Nix 244 | 245 | Though covering Nix comprehensively is beyond the scope of this document, we'll 246 | go over a few commands illustrating some usage of Nix with this project. 247 | 248 | ** Searching Nix files 249 | 250 | Each of the Nix files in this project (files with a ".nix" extension) contains 251 | exactly one Nix expression. This expression evaluates to one of the following 252 | values: 253 | 254 | - simple primitives and functions 255 | - /derivations/ of packages that can be built and installed with Nix 256 | - containers of values, allowing a single value to provide multiple values of 257 | different types, including more containers of values. 258 | 259 | Once you learn the Nix language, you can read these files to see what kind of 260 | values they build. We can use the =nix search= command to see what package 261 | derivations a Nix expression contains. For example from the root directory of 262 | this project, we can execute: 263 | 264 | #+name: nix-derivation-show 265 | #+begin_src sh :dir .. :results output silent :exports none 266 | nix show-derivation --file default.nix >/dev/null 2>&1 267 | #+end_src 268 | 269 | #+begin_src sh :eval no 270 | nix search --file default.nix --no-cache 271 | #+end_src 272 | 273 | #+name: nix-search 274 | #+begin_src sh :dir .. :results output :exports results :post crop(text=*this*, first-n=9, last-n=0) 275 | nix search --file default.nix --no-cache | ansifilter 276 | #+end_src 277 | 278 | #+results: nix-search 279 | : * direnv (direnv) 280 | : A shell extension that manages your environment 281 | : 282 | : * direnv-nix-lorelei (direnv-nix-lorelei) 283 | : Alternative Nix functions for Direnv 284 | : 285 | 286 | If you don't get the results above, see the [[#nix-drv][section on understanding derivations]] 287 | for an explanation of a likely problem and workaround. 288 | 289 | Note that because for extremely large Nix expressions, searching can be slow, 290 | =nix search= by default returns results from searching an indexed cache. This 291 | cache is updated explicitly (with an =--update-cache= switch) but may be 292 | inconsistent with what you really want to search. It can be confusing to get 293 | incorrect results due to an inconsistent cache. However, because small local 294 | projects rarely have that many package derivations we don't really need the 295 | cache, and can bypass it with the =--no-cache= switch, as used above. This 296 | guarantees accurate results that are fast enough. So for the purposes of this 297 | project, it's recommended to always use =--no-cache=. 298 | 299 | The output of =nix search= is formatted as 300 | 301 | #+begin_example 302 | ,* attribute-path (name-of-package) 303 | Short description of package 304 | #+end_example 305 | 306 | /Attribute paths/ are used to select values from Nix sets that might be nested. 307 | A dot delimits /attributes/ in the path. For instance an attribute path of =a.b= 308 | selects a value from a set with an =a= attribute that has set with a =b= 309 | attribute, that then has the value to select. 310 | 311 | If the Nix expression we're searching evaluates to a single derivation (not in a 312 | container), the attribute path will be missing from the =nix search= result. 313 | 314 | Many Nix commands evaluate Nix files. If you specify a directory instead, the 315 | command will look for a =default.nix= file within to evaluate. So from the root 316 | directory of this project, we could use =.= instead of =default.nix=: 317 | 318 | #+name: nix-search-alt 319 | #+begin_src sh :dir .. :results output silent 320 | nix search --file . --no-cache 321 | #+end_src 322 | 323 | In the remainder of this document, we'll use =.= instead of =default.nix= since 324 | this is conventional for Nix. 325 | 326 | ** Building Nix expressions 327 | 328 | The following result is one returned by our prior execution of ~nix search 329 | --no-cache --file .~: 330 | 331 | #+name: nix-search-specific 332 | #+begin_src sh :dir .. :results output :exports results :noweb yes 333 | nix search --no-cache --file . | ansifilter \ 334 | | grep --color=never --after-context=1 '* <> (' 335 | #+end_src 336 | 337 | #+results: nix-search-specific 338 | : * direnv-nix-lorelei (direnv-nix-lorelei) 339 | : Alternative Nix functions for Direnv 340 | 341 | We can see that a package named {{{package-name}}} can be accessed with the 342 | {{{package-attr}}} attribute path in the Nix expression in the project root's 343 | =default.nix=. Not shown in the search results above, this package happens to 344 | provide the {{{package-type}}} {{{package-target}}}. 345 | 346 | We can build this package with =nix build= from the project root: 347 | 348 | #+name: nix-build 349 | #+begin_src sh :dir .. :results output silent :noweb yes 350 | nix build --file . <> 351 | #+end_src 352 | 353 | The positional arguments to =nix build= are /installables/, which can be 354 | referenced by attribute paths. If you supply none then all derivations found are 355 | built by default. 356 | 357 | All packages built by Nix are stored in =/nix/store=. Nix won't rebuild packages 358 | found there. Once a package is built, its content in =/nix/store= is read-only 359 | (until the package is garbage collected, discussed later). 360 | 361 | After a successful call of =nix build=, you'll see one or more symlinks for each 362 | package requested in the current working directory. These symlinks by default 363 | have a name prefixed with "result" and point back to the respective build in 364 | =/nix/store=: 365 | 366 | #+name: nix-build-link 367 | #+begin_src sh :dir .. :results output :exports both 368 | readlink result* 369 | #+end_src 370 | 371 | #+results: nix-build-link 372 | : /nix/store/q44il55npbs3pj2zpg0f828hy6miysn0-direnv-nix-lorelei 373 | 374 | Following these symlinks, we can see the files the project provides: 375 | 376 | #+name: nix-build-tree 377 | #+begin_src sh :dir .. :results output :exports both :post crop(text=*this*, first-n=10, last-n=0) 378 | tree -l result* 379 | #+end_src 380 | 381 | #+results: nix-build-tree 382 | : result 383 | : └── share 384 | : └── direnv-nix-lorelei 385 | : └── nix-lorelei.bash 386 | : 387 | : 2 directories, 1 file 388 | 389 | It's common to configure these "result" symlinks as ignored in source control 390 | tools (for instance, for Git within a =.gitignore= file). 391 | 392 | =nix build= has a =--no-link= switch in case you want to build packages without 393 | creating "result" symlinks. To get the paths where your packages are located, 394 | you can use =nix path-info= after a successful build: 395 | 396 | #+name: nix-build-path 397 | #+begin_src sh :dir .. :results output :exports both :noweb yes 398 | nix path-info --file . <> 399 | #+end_src 400 | 401 | #+results: nix-build-path 402 | : /nix/store/q44il55npbs3pj2zpg0f828hy6miysn0-direnv-nix-lorelei 403 | 404 | ** Running commands 405 | 406 | We can run commands in Nix-curated environments with =nix run=. Nix will take 407 | executables found in packages, put them in an environment's =PATH=, and then 408 | execute a user-specified command. 409 | 410 | With =nix run=, you don't even have to build the package first with =nix build= 411 | or mess around with "result" symlinks. =nix run= will build the project if it's 412 | not yet been built. 413 | 414 | For example, to get the help message for the {{{run-target}}} executable 415 | provided by the {{{run-name}}} package selected by the {{{run-attr}}} attribute 416 | path from {{{run-src}}}, we can call the following: 417 | 418 | #+name: nix-run 419 | #+begin_src sh :dir .. :results output :exports both :noweb yes :post crop(text=*this*, first-n=5, last-n=0) 420 | nix run \ 421 | --file <> \ 422 | <> \ 423 | --command <> --help 424 | #+end_src 425 | 426 | #+results: nix-run 427 | : direnv v2.28.0 428 | : Usage: direnv COMMAND [...ARGS] 429 | : 430 | : Available commands 431 | : ------------------ 432 | : … 433 | 434 | Thus far, the argument of the =--file= switch has always referenced a Nix file 435 | on our local filesystem. However, it's possible to reference a Nix expression 436 | downloaded from the internet. The Nix ecosystem is supported by a giant GitHub 437 | repository of Nix expressions called [[nixpkgs][Nixpkgs]]. Special branches of this 438 | repository are considered /channels/ in the Nix ecosystem. A Nixpkgs branch of 439 | "{{{nixos-release}}}" can be referenced by "channel:{{{nixos-release}}}" for 440 | =nix= subcommands that accept a =--file= switch. 441 | 442 | Again, as with =nix build=, attribute paths are specified as positional 443 | arguments to select packages. 444 | 445 | The command to run is specified after the =--command= switch. =nix run= runs the 446 | command in a shell set up with a =PATH= environment variable including all the 447 | =bin= directories provided by the selected packages. 448 | 449 | =nix run= also supports an =--ignore-environment= flag that restricts =PATH= to 450 | only packages selected, rather than extending the =PATH= of the caller's 451 | environment. With =--ignore-environment=, the invocation is more sandboxed. 452 | 453 | ** Installing and uninstalling programs 454 | 455 | We've seen that we can build programs with =nix build= and then execute them 456 | using the "result" symlink (=result/bin/*=). Additionally, we've seen that you 457 | can run programs with =nix run=. But these additional steps and 458 | switches/arguments can feel extraneous. It would be nice if we could just have 459 | the programs on our =PATH=. This is what =nix-env= is for. 460 | 461 | =nix-env= maintains a symlink tree, called a /profile/, of installed programs. 462 | The active profile is pointed to by a symlink at =~/.nix-profile=. By default, 463 | this profile points to =/nix/var/nix/profiles/per-user/$USER/profile=. But you 464 | can point your =~/.nix-profile= to any writable location with the 465 | =--switch-profile= switch: 466 | 467 | #+begin_src sh :eval no 468 | nix-env --switch-profile /nix/var/nix/profiles/per-user/$USER/another-profile 469 | #+end_src 470 | 471 | This way, you can just put =~/.nix-profile/bin= on your =PATH=, and any programs 472 | installed in your currently active profile will be available for interactive use 473 | or scripts. 474 | 475 | We can query what's installed in the active profile with the =--query= switch: 476 | 477 | #+name: nix-env-query-1 478 | #+begin_src sh :session env :results output silent 479 | nix-env --query 480 | #+end_src 481 | 482 | To install the {{{package-target}}} {{{package-type}}}, which is accessed by the 483 | {{{package-attr}}} in our top-level =default.nix= file, we'd run the following: 484 | 485 | #+name: nix-env-install 486 | #+begin_src sh :session env :results output :exports both :noweb yes :post crop(text=*this*, first-n=1, last-n=3) 487 | nix-env --install --file . --attr <> 2>&1 488 | #+end_src 489 | 490 | #+results: nix-env-install 491 | : installing 'direnv-nix-lorelei' 492 | 493 | We can see this installation by querying what's been installed: 494 | 495 | #+name: nix-env-query-2 496 | #+begin_src sh :session env :results output :exports both 497 | nix-env --query 498 | #+end_src 499 | 500 | #+results: nix-env-query-2 501 | : direnv-nix-lorelei 502 | 503 | And if we want to uninstall a program from our active profile, we do so by its 504 | name, in this case {{{package-name}}}: 505 | 506 | #+name: nix-env-uninstall 507 | #+begin_src sh :session env :results output :exports both :noweb yes 508 | nix-env --uninstall <> 2>&1 509 | #+end_src 510 | 511 | #+results: nix-env-uninstall 512 | : uninstalling 'direnv-nix-lorelei' 513 | 514 | Note that we've installed our package using its attribute path 515 | ({{{package-attr}}}) within the referenced Nix expression. But we uninstall it 516 | using the package name ({{{package-name}}}), which may or may not be the same as 517 | the attribute path. When a package is installed, Nix keeps no reference to the 518 | expression that evaluated to the derivation of the installed package. The 519 | attribute path is only relevant to this expression. In fact, two different 520 | expressions could evaluate to the same derivation, but use different attribute 521 | paths. This is why we uninstall packages by their package name. 522 | 523 | Also, if you look at the location for your profile, you'll see that Nix retains 524 | the symlink trees of previous generations of your profile. In fact you can even 525 | rollback to a previous profile with the =--rollback= switch. You can delete old 526 | generations of your profile with the =--delete-generations= switch. 527 | 528 | See the [[nix-env][documentation for =nix-env=]] for more details. 529 | 530 | ** Garbage collection 531 | 532 | Every time you build a new version of your code, it's stored in =/nix/store=. 533 | There is a command called =nix-collect-garbage= that purges unneeded packages. 534 | Programs that should not be removed by =nix-collect-garbage= can by found by 535 | starting with symlinks stored as /garbage collection (GC) roots/ under three 536 | locations: 537 | 538 | - =/nix/var/nix/gcroots= 539 | - =/nix/var/nix/profiles= 540 | - =/nix/var/nix/manifests=. 541 | 542 | For each package, Nix is aware of all references back to other packages in 543 | =/nix/store=, whether in text files or binaries. This helps Nix assure that 544 | dependencies of packages linked as GC roots won't be deleted. 545 | 546 | Each "result" symlink created by a =nix build= invocation has a symlink in 547 | =/nix/var/nix/gcroots/auto= pointing back it. So we've got symlinks in 548 | =/nix/var/nix/gcroots/auto= pointing to "result" symlinks in our projects, which 549 | then reference the actual built project in =/nix/store=. These chains of 550 | symlinks prevent packages built by =nix build= from being garbage collected. 551 | 552 | If you want a package you've built with =nix build= to be garbage collected, 553 | delete the "result" symlink created before calling =nix-collect-garbage=. 554 | Breaking symlink chains under =/nix/var/nix/gcroots= removes protection from 555 | garbage collection. =nix-collect-garbage= will clean up broken symlinks when it 556 | runs. 557 | 558 | Note that everything under =/nix/var/nix/profiles= is considered a GC root as 559 | well. This is why users by convention use this location to store their =nix-env= 560 | profiles. 561 | 562 | Also, note if you delete a “result*” link and call =nix-collect-garbage=, though 563 | some garbage may be reclaimed, you may find that an old =nix-env= profile is 564 | keeping the program alive. As a convenience, =nix-collect-garbage= has a 565 | =--delete-old= switch that will delete these old profiles (it just calls 566 | ~nix-env --delete-generations~ on your behalf). 567 | 568 | It's also good to know that =nix-collect-garbage= won't delete packages 569 | referenced by any running processes. In the case of =nix run= no garbage 570 | collection root symlink is created under =/nix/var/nix/gcroots=, but while =nix 571 | run= is running =nix-collect-garbage= won't delete packages needed by the 572 | running command. However, once the =nix run= call exits, any packages pulled 573 | from a substitutor or built locally are candidates for deletion by 574 | =nix-collect-garbage=. If you called =nix run= again after garbage collecting, 575 | those packages may be pulled or built again. 576 | 577 | ** Understanding derivations 578 | :PROPERTIES: 579 | :CUSTOM_ID: nix-drv 580 | :END: 581 | 582 | We haven't detailed what happens when we build a Nix expression that evaluates 583 | to a package derivation. There are two important steps: 584 | 585 | 1. /instantiating/ the derivation 586 | 2. /realizing/ the instantiated derivation, which builds the final package. 587 | 588 | An instantiated derivation is effectively a script stored in =/nix/store= that 589 | Nix can run to build the final package (which also ends up in =/nix/store=). 590 | These instantiated derivations have a ".drv" extension, and if you look in 591 | =/nix/store= you may find some. Instantiated derivations have references to all 592 | necessary build dependencies, also in =/nix/store=, which means that everything 593 | is physically in place in =/nix/store= to build the package (no network 594 | connectivity is needed to realize an instantiated derivation). 595 | 596 | Note that both =nix build= and =nix run= perform both instantiation and 597 | realization of a derivation, so for the most part, we don't have to worry about 598 | the difference between instantiating and realizing a derivation. 599 | 600 | However, you may encounter a Nix expression where =nix search= returns nothing, 601 | though you're sure that there are derivations to select out. In this case, the 602 | Nix expression is using an advanced technique that unfortunately hides 603 | attributes from =nix search= until some derivations are instantiated into 604 | =/nix/store=. We can force the instantiation of these derivations without 605 | realizing their packages with the following command: 606 | 607 | #+name: nix-derivation-show-again 608 | #+begin_src sh :eval no 609 | nix show-derivation --file default.nix 610 | #+end_src 611 | 612 | Once these derivations are instantiated, you may get more results with =nix 613 | search= for the occasional Nix expression that uses some advanced techniques. 614 | 615 | ** Lazy evaluation 616 | 617 | We haven't made a big deal of it, but the Nix language is /lazily evaluated/. 618 | This allows a single Nix expression to refer to several thousand packages, but 619 | without requiring us to evaluate everything when selecting out packages by 620 | attribute paths. In fact, the entire NixOS operating system is based heavily on 621 | a single single expression managed in a Git repository called [[nixpkgs][Nixpkgs]]. 622 | 623 | * Next steps 624 | 625 | This document has covered a fraction of Nix usage, hopefully enough to introduce 626 | Nix in the context of [[file:../README.org][this project]]. 627 | 628 | An obvious place to start learning more about Nix is [[nix-learn][the official documentation]]. 629 | The author of this project also maintains another project with [[nix-tutorial][a small tutorial 630 | on Nix]]. This tutorial covers the Nix expression language in more detail. 631 | 632 | All the commands we've covered have more switches and options. See the 633 | respective man pages for more. Also, we didn't cover =nix-shell=, which can be 634 | used for setting up development environments. And we didn't cover much of 635 | [[nixpkgs][Nixpkgs]], the gigantic repository of community-curated Nix expressions. 636 | 637 | The Nix ecosystem is vast. This project and documentation illustrates just a 638 | small sample of what Nix can do. 639 | 640 | * Org-mode teardown :noexport: 641 | 642 | #+call: cleanup() 643 | -------------------------------------------------------------------------------- /doc/nix.org.el: -------------------------------------------------------------------------------- 1 | ((package-attr . "direnv-nix-lorelei") 2 | (package-name . "direnv-nix-lorelei") 3 | (package-type . "library") 4 | (package-target . "nix-alt.sh") 5 | (run-src . ".") 6 | (run-attr . "direnv") 7 | (run-name . "direnv") 8 | (run-target . "direnv") 9 | (nixos-release . "nixos-21.05")) 10 | -------------------------------------------------------------------------------- /nix/ci.nix: -------------------------------------------------------------------------------- 1 | import ../. 2 | -------------------------------------------------------------------------------- /nix/default.nix: -------------------------------------------------------------------------------- 1 | { externalOverrides ? {} 2 | }: 3 | 4 | let 5 | 6 | external = import ./external // externalOverrides; 7 | 8 | nix-project = import external.nix-project; 9 | 10 | nixpkgs = import external.nixpkgs-stable { 11 | config = {}; 12 | overlays = [overlay]; 13 | }; 14 | 15 | lorri-stock = nixpkgs.applyPatches { 16 | name = "lorri-stock"; 17 | src = external.lorri; 18 | patches = [./env_name_cleanup.patch]; 19 | }; 20 | 21 | lorri-patched = nixpkgs.applyPatches { 22 | name = "lorri-patched"; 23 | src = external.lorri; 24 | patches = [ 25 | ./remove_trace.patch 26 | ./env_name_cleanup.patch 27 | ]; 28 | }; 29 | 30 | overlay = self: _super: nix-project // rec { 31 | lorri-runtime = 32 | self.callPackage 33 | (import "${lorri-stock}/nix/runtime.nix") 34 | {}; 35 | lorri-eval-stock = {src}: 36 | (import "${lorri-stock}/src/logged-evaluation.nix") 37 | { inherit src; runTimeClosure = lorri-runtime; }; 38 | lorri-eval-patched = {src}: 39 | (import "${lorri-patched}/src/logged-evaluation.nix") 40 | { inherit src; runTimeClosure = lorri-runtime; }; 41 | lorri-envrc = 42 | "${lorri-stock}/src/ops/direnv/envrc.bash"; 43 | direnv-nix-lorelei = 44 | self.callPackage (import ./direnv-nix-lorelei.nix) {}; 45 | direnv-nix-lorelei-home = ./home.nix; 46 | direnv-nix-lorelei-test = self.callPackage (import ./test/test.nix) {}; 47 | }; 48 | 49 | distribution = { 50 | inherit (nixpkgs) 51 | direnv 52 | direnv-nix-lorelei 53 | direnv-nix-lorelei-home; 54 | }; 55 | 56 | build = distribution // { 57 | inherit (nixpkgs) 58 | direnv-nix-lorelei-test 59 | lorri-eval-patched 60 | lorri-eval-stock 61 | ; 62 | }; 63 | 64 | in { inherit build distribution nix-project nixpkgs; } 65 | -------------------------------------------------------------------------------- /nix/direnv-nix-lorelei.nix: -------------------------------------------------------------------------------- 1 | { coreutils 2 | , findutils 3 | , gnused 4 | , jq 5 | , lib 6 | , lorri-envrc 7 | , lorri-eval-stock 8 | , lorri-eval-patched 9 | , nix-project-lib 10 | , path 11 | , xxHash 12 | }: 13 | 14 | let 15 | name = "direnv-nix-lorelei"; 16 | meta.description = "Alternative Nix functions for Direnv"; 17 | packagePath = "direnv-nix-lorelei"; 18 | baseName = "nix-lorelei"; 19 | buildSource = lib.sourceFilesBySuffices ./. [ 20 | ".json" 21 | ".nix" 22 | ".patch" 23 | ]; 24 | 25 | in 26 | 27 | nix-project-lib.writeShellCheckedShareLib name packagePath 28 | { 29 | inherit meta baseName; 30 | } 31 | '' 32 | # shellcheck shell=bash 33 | 34 | _nixgc_usage() 35 | { 36 | "${coreutils}/bin/cat" - < "$build_proof" 276 | } 277 | 278 | _nixgc_record_hashes() 279 | { 280 | "${xxHash}/bin/xxhsum" "$@" > "$hash_cache" 281 | } 282 | 283 | _nixgc_rebuild_needed_hash() 284 | { 285 | local hash_cache="$1"; shift 286 | if ! [ -f "$hash_cache" ] 287 | then 288 | log_status "initializing hashes: $hash_cache" 289 | return 0 290 | fi 291 | if ! "${xxHash}/bin/xxhsum" --check "$hash_cache" >/dev/null 292 | then 293 | log_status "hash check invalidated cache" 294 | return 0 295 | else 296 | log_status "no watched hashes changed" 297 | return 1 298 | fi 299 | } 300 | 301 | _nixgc_watched_from_file() 302 | { 303 | local build_proof="$1" 304 | local hash_cache="$2" 305 | "${coreutils}/bin/cat" "$build_proof" 306 | "${gnused}/bin/sed" -n 's/.*\s\+\(.*\)/\1/p' < "$hash_cache" 307 | } 308 | 309 | _nixgc_rebuild() 310 | { 311 | local env_cache="$1" 312 | local shell_file= 313 | shell_file="$("${coreutils}/bin/readlink" -f "$2")" 314 | local keep_last="$3" 315 | local auto_watch_eval="$4" 316 | # DESIGN: https://github.com/koalaman/shellcheck/issues/817 317 | # shellcheck disable=SC2034 318 | local -n _auto_watch="$5" 319 | 320 | local cache_root 321 | cache_root="$("${coreutils}/bin/dirname" "$env_cache")" 322 | 323 | log_status "rebuilding with Nix" 324 | "${coreutils}/bin/rm" --recursive --force "$env_cache" 325 | "${coreutils}/bin/mkdir" --parents "$cache_root" 326 | 327 | local store_path=() 328 | local build_err=() 329 | _nixgc_build_autowatching \ 330 | "$shell_file" "$auto_watch_eval" store_path _auto_watch build_err 331 | if [ -z "''${store_path[0]}" ] 332 | then 333 | for l in "''${build_err[@]}" 334 | do log_error "$l" 335 | done 336 | _nixgc_fail "ERROR: Nix build failed" 337 | fi 338 | 339 | local _pwd; 340 | _pwd="$(pwd)" 341 | _pwd="$("${coreutils}/bin/readlink" -f "$_pwd")" 342 | local pwd_hash 343 | pwd_hash="''${store_path[0]}" 344 | pwd_hash="''${pwd_hash#/nix/store/}" 345 | pwd_hash="''${pwd_hash%%-*}" 346 | local escaped_pwd="''${_pwd/\/}" 347 | escaped_pwd="''${escaped_pwd//\//:}" 348 | 349 | "${coreutils}/bin/ln" --force --symbolic --no-target-directory \ 350 | "''${store_path[0]}" \ 351 | "$env_cache-$pwd_hash" 352 | 353 | "${coreutils}/bin/ln" --force --symbolic --no-target-directory \ 354 | "$env_cache-$pwd_hash" \ 355 | "$env_cache" 356 | 357 | local gcroot="/nix/var/nix/gcroots/per-user/$USER" 358 | "${coreutils}/bin/ln" --force --symbolic --no-target-directory \ 359 | "$env_cache-$pwd_hash" \ 360 | "$gcroot/$escaped_pwd:$pwd_hash" 361 | 362 | "${findutils}/bin/find" "$cache_root" \ 363 | -type l -wholename "$env_cache-*" -printf "%T+/%p\n" \ 364 | | "${coreutils}/bin/sort" --reverse \ 365 | | "${coreutils}/bin/tail" --lines=+"$(("$keep_last" + 1))" \ 366 | | { 367 | while read -r line 368 | do 369 | local f="''${line#*/}" 370 | log_status "allowing GC (keeping last $keep_last): $f" 371 | "${coreutils}/bin/rm" "$f" 372 | done 373 | } 374 | 375 | "${findutils}/bin/find" -L "$gcroot" \ 376 | -type l \ 377 | -name "$escaped_pwd:*" \ 378 | -exec "${coreutils}/bin/rm" {} + 379 | } 380 | 381 | _nixgc_build_autowatching() 382 | { 383 | local shell_file="$1" 384 | local auto_watch_eval="$2" 385 | local -n _out="$3" 386 | local -n _watched="$4" 387 | local -n _build_err="$5" 388 | local both=() 389 | local err=() 390 | mapfile -t both < <({ 391 | { _nixgc_build "$shell_file" "$auto_watch_eval" \ 392 | | _nixgc_capture o ; 393 | } 3>&1 1>&2 2>&3 | _nixgc_capture e ; 394 | } 2>&1) 395 | # DESIGN: https://github.com/koalaman/shellcheck/issues/817 396 | # shellcheck disable=SC2034 397 | mapfile -t _out < <(printf "%s\n" "''${both[@]}" | _nixgc_select_line o) 398 | # DESIGN: https://github.com/koalaman/shellcheck/issues/817 399 | # shellcheck disable=SC2034 400 | mapfile -t err < <(printf "%s\n" "''${both[@]}" | _nixgc_select_line e) 401 | # DESIGN: https://github.com/koalaman/shellcheck/issues/817 402 | # shellcheck disable=SC2034 403 | mapfile -t _watched < <(printf "%s\n" "''${err[@]}" \ 404 | | _nixgc_capture_autowatchable) 405 | # DESIGN: https://github.com/koalaman/shellcheck/issues/817 406 | # shellcheck disable=SC2034 407 | mapfile -t _build_err < <(printf "%s\n" "''${err[@]}" \ 408 | | "${gnused}/bin/sed" -n '/^error:/,$p') 409 | } 410 | 411 | _nixgc_build() 412 | { 413 | local shell_file="$1" 414 | local auto_watch_eval="$2" 415 | IN_NIX_SHELL=1 \ 416 | nix-build \ 417 | --show-trace \ 418 | --verbose --verbose \ 419 | --no-out-link \ 420 | --arg src "$shell_file" \ 421 | --expr "((import ${buildSource} {}).build.lorri-eval-$auto_watch_eval)" 422 | } 423 | 424 | _nixgc_select_line() 425 | { 426 | local prefix="$1" 427 | "${gnused}/bin/sed" -n "s/^$prefix: \(.*\)$/\1/p" 428 | } 429 | 430 | _nixgc_capture() 431 | { 432 | local prefix="$1" 433 | "${coreutils}/bin/stdbuf" -oL \ 434 | "${gnused}/bin/sed" -n "s/\(.*\)/$prefix: \1/p" 435 | } 436 | 437 | _nixgc_capture_autowatchable() 438 | { 439 | "${gnused}/bin/sed" -n " 440 | # find paths and substitute the line for them 441 | s/\(copied source\|evaluating file\|trace: lorri read:\)[^']*'\([^']\+\)'.*/\2/; 442 | # delete /nix/store paths, lines with no found paths, and empty lines 443 | /^\(\/nix\/\|[^\/]\|$\)/d; 444 | # print paths found not in /nix/store 445 | p 446 | " | { 447 | while read -r f 448 | do 449 | if [ -d "$f" ] 450 | then echo "$f/default.nix" 451 | else echo "$f" 452 | fi 453 | done 454 | } | "${coreutils}/bin/sort" -u 455 | } 456 | 457 | _nixgc_import_env() 458 | { 459 | local EVALUATION_ROOT="$1" 460 | . "${lorri-envrc}" 461 | } 462 | 463 | _nixgc_fail() 464 | { 465 | log_error "$@" 466 | exit 1 467 | } 468 | '' 469 | -------------------------------------------------------------------------------- /nix/env_name_cleanup.patch: -------------------------------------------------------------------------------- 1 | diff --git a/src/logged-evaluation.nix b/src/logged-evaluation.nix 2 | --- a/src/logged-evaluation.nix 3 | +++ b/src/logged-evaluation.nix 4 | @@ -55,7 +55,7 @@ let 5 | # actual environment from being deleted. 6 | keep-env-hack = drv: derivation ( 7 | drv.drvAttrs // { 8 | - name = "lorri-keep-env-hack-${drv.name}"; 9 | + name = "lorelei-${drv.name}"; 10 | 11 | origExtraClosure = drv.extraClosure or []; 12 | extraClosure = runtimeCfg.closure; 13 | -------------------------------------------------------------------------------- /nix/external/default.nix: -------------------------------------------------------------------------------- 1 | let 2 | 3 | srcs = import ./sources.nix; 4 | 5 | nixpkgs-bootstrap = import srcs.nixpkgs { config = {}; overlays = []; }; 6 | isDarwin = nixpkgs-bootstrap.stdenv.isDarwin; 7 | 8 | nixpkgs-stable-linux = srcs.nixpkgs; 9 | nixpkgs-stable-darwin = srcs.nixpkgs-darwin; 10 | nixpkgs-stable = 11 | if isDarwin then nixpkgs-stable-darwin else nixpkgs-stable-linux; 12 | 13 | srcsMerged = srcs // { 14 | inherit nixpkgs-stable nixpkgs-stable-linux nixpkgs-stable-darwin; 15 | }; 16 | 17 | in builtins.removeAttrs srcsMerged ["nixpkgs" "nixpkgs-darwin"] 18 | -------------------------------------------------------------------------------- /nix/external/sources.json: -------------------------------------------------------------------------------- 1 | { 2 | "lorri": { 3 | "branch": "canon", 4 | "description": "Your project's nix-env", 5 | "homepage": "", 6 | "owner": "nix-community", 7 | "repo": "lorri", 8 | "rev": "780c9a9825969f1bd068690717341ba1d5a9538f", 9 | "sha256": "1njp38cvzkz1aq4nymdkxmwan8y17raqqq2qrclavdb2g492dwy7", 10 | "type": "tarball", 11 | "url": "https://github.com/nix-community/lorri/archive/780c9a9825969f1bd068690717341ba1d5a9538f.tar.gz", 12 | "url_template": "https://github.com///archive/.tar.gz" 13 | }, 14 | "nix-project": { 15 | "branch": "main", 16 | "description": "Tools to manage a Nix-based project", 17 | "homepage": "", 18 | "owner": "shajra", 19 | "repo": "nix-project", 20 | "rev": "1604510c6972465635408e3279e59b2fda0ef595", 21 | "sha256": "16zxags4rnlbc29wbwyqjfcfksnrjxw2n46n4v9jl2nal94qgha9", 22 | "type": "tarball", 23 | "url": "https://github.com/shajra/nix-project/archive/1604510c6972465635408e3279e59b2fda0ef595.tar.gz", 24 | "url_template": "https://github.com///archive/.tar.gz" 25 | }, 26 | "nixpkgs": { 27 | "branch": "nixos-21.05", 28 | "description": "A read-only mirror of NixOS/nixpkgs tracking the released channels. Send issues and PRs to", 29 | "homepage": "https://github.com/NixOS/nixpkgs", 30 | "owner": "NixOS", 31 | "repo": "nixpkgs", 32 | "rev": "6120ac5cd201f6cb593d1b80e861be0342495be9", 33 | "sha256": "04mrjxr1qsdcgcryx7yy72cgcw14c0770gfcgzrdfpnvmjdgbi9i", 34 | "type": "tarball", 35 | "url": "https://github.com/NixOS/nixpkgs/archive/6120ac5cd201f6cb593d1b80e861be0342495be9.tar.gz", 36 | "url_template": "https://github.com///archive/.tar.gz" 37 | }, 38 | "nixpkgs-darwin": { 39 | "branch": "nixpkgs-21.05-darwin", 40 | "description": "A read-only mirror of NixOS/nixpkgs tracking the released channels. Send issues and PRs to", 41 | "homepage": "https://github.com/NixOS/nixpkgs", 42 | "owner": "NixOS", 43 | "repo": "nixpkgs", 44 | "rev": "3397f0ede9ea2ded1f8b6fa689dda71a7a67b806", 45 | "sha256": "0dx5hbwjbwy404ng5m3dv2rdfbsw58gxblcxfgdwmpyn2qx14sip", 46 | "type": "tarball", 47 | "url": "https://github.com/NixOS/nixpkgs/archive/3397f0ede9ea2ded1f8b6fa689dda71a7a67b806.tar.gz", 48 | "url_template": "https://github.com///archive/.tar.gz" 49 | } 50 | } 51 | -------------------------------------------------------------------------------- /nix/external/sources.nix: -------------------------------------------------------------------------------- 1 | # This file has been generated by Niv. 2 | 3 | let 4 | 5 | # 6 | # The fetchers. fetch_ fetches specs of type . 7 | # 8 | 9 | fetch_file = pkgs: name: spec: 10 | let 11 | name' = sanitizeName name + "-src"; 12 | in 13 | if spec.builtin or true then 14 | builtins_fetchurl { inherit (spec) url sha256; name = name'; } 15 | else 16 | pkgs.fetchurl { inherit (spec) url sha256; name = name'; }; 17 | 18 | fetch_tarball = pkgs: name: spec: 19 | let 20 | name' = sanitizeName name + "-src"; 21 | in 22 | if spec.builtin or true then 23 | builtins_fetchTarball { name = name'; inherit (spec) url sha256; } 24 | else 25 | pkgs.fetchzip { name = name'; inherit (spec) url sha256; }; 26 | 27 | fetch_git = name: spec: 28 | let 29 | ref = 30 | if spec ? ref then spec.ref else 31 | if spec ? branch then "refs/heads/${spec.branch}" else 32 | if spec ? tag then "refs/tags/${spec.tag}" else 33 | abort "In git source '${name}': Please specify `ref`, `tag` or `branch`!"; 34 | in 35 | builtins.fetchGit { url = spec.repo; inherit (spec) rev; inherit ref; }; 36 | 37 | fetch_local = spec: spec.path; 38 | 39 | fetch_builtin-tarball = name: throw 40 | ''[${name}] The niv type "builtin-tarball" is deprecated. You should instead use `builtin = true`. 41 | $ niv modify ${name} -a type=tarball -a builtin=true''; 42 | 43 | fetch_builtin-url = name: throw 44 | ''[${name}] The niv type "builtin-url" will soon be deprecated. You should instead use `builtin = true`. 45 | $ niv modify ${name} -a type=file -a builtin=true''; 46 | 47 | # 48 | # Various helpers 49 | # 50 | 51 | # https://github.com/NixOS/nixpkgs/pull/83241/files#diff-c6f540a4f3bfa4b0e8b6bafd4cd54e8bR695 52 | sanitizeName = name: 53 | ( 54 | concatMapStrings (s: if builtins.isList s then "-" else s) 55 | ( 56 | builtins.split "[^[:alnum:]+._?=-]+" 57 | ((x: builtins.elemAt (builtins.match "\\.*(.*)" x) 0) name) 58 | ) 59 | ); 60 | 61 | # The set of packages used when specs are fetched using non-builtins. 62 | mkPkgs = sources: system: 63 | let 64 | sourcesNixpkgs = 65 | import (builtins_fetchTarball { inherit (sources.nixpkgs) url sha256; }) { inherit system; }; 66 | hasNixpkgsPath = builtins.any (x: x.prefix == "nixpkgs") builtins.nixPath; 67 | hasThisAsNixpkgsPath = == ./.; 68 | in 69 | if builtins.hasAttr "nixpkgs" sources 70 | then sourcesNixpkgs 71 | else if hasNixpkgsPath && ! hasThisAsNixpkgsPath then 72 | import {} 73 | else 74 | abort 75 | '' 76 | Please specify either (through -I or NIX_PATH=nixpkgs=...) or 77 | add a package called "nixpkgs" to your sources.json. 78 | ''; 79 | 80 | # The actual fetching function. 81 | fetch = pkgs: name: spec: 82 | 83 | if ! builtins.hasAttr "type" spec then 84 | abort "ERROR: niv spec ${name} does not have a 'type' attribute" 85 | else if spec.type == "file" then fetch_file pkgs name spec 86 | else if spec.type == "tarball" then fetch_tarball pkgs name spec 87 | else if spec.type == "git" then fetch_git name spec 88 | else if spec.type == "local" then fetch_local spec 89 | else if spec.type == "builtin-tarball" then fetch_builtin-tarball name 90 | else if spec.type == "builtin-url" then fetch_builtin-url name 91 | else 92 | abort "ERROR: niv spec ${name} has unknown type ${builtins.toJSON spec.type}"; 93 | 94 | # If the environment variable NIV_OVERRIDE_${name} is set, then use 95 | # the path directly as opposed to the fetched source. 96 | replace = name: drv: 97 | let 98 | saneName = stringAsChars (c: if isNull (builtins.match "[a-zA-Z0-9]" c) then "_" else c) name; 99 | ersatz = builtins.getEnv "NIV_OVERRIDE_${saneName}"; 100 | in 101 | if ersatz == "" then drv else 102 | # this turns the string into an actual Nix path (for both absolute and 103 | # relative paths) 104 | if builtins.substring 0 1 ersatz == "/" then /. + ersatz else /. + builtins.getEnv "PWD" + "/${ersatz}"; 105 | 106 | # Ports of functions for older nix versions 107 | 108 | # a Nix version of mapAttrs if the built-in doesn't exist 109 | mapAttrs = builtins.mapAttrs or ( 110 | f: set: with builtins; 111 | listToAttrs (map (attr: { name = attr; value = f attr set.${attr}; }) (attrNames set)) 112 | ); 113 | 114 | # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/lists.nix#L295 115 | range = first: last: if first > last then [] else builtins.genList (n: first + n) (last - first + 1); 116 | 117 | # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/strings.nix#L257 118 | stringToCharacters = s: map (p: builtins.substring p 1 s) (range 0 (builtins.stringLength s - 1)); 119 | 120 | # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/strings.nix#L269 121 | stringAsChars = f: s: concatStrings (map f (stringToCharacters s)); 122 | concatMapStrings = f: list: concatStrings (map f list); 123 | concatStrings = builtins.concatStringsSep ""; 124 | 125 | # https://github.com/NixOS/nixpkgs/blob/8a9f58a375c401b96da862d969f66429def1d118/lib/attrsets.nix#L331 126 | optionalAttrs = cond: as: if cond then as else {}; 127 | 128 | # fetchTarball version that is compatible between all the versions of Nix 129 | builtins_fetchTarball = { url, name ? null, sha256 }@attrs: 130 | let 131 | inherit (builtins) lessThan nixVersion fetchTarball; 132 | in 133 | if lessThan nixVersion "1.12" then 134 | fetchTarball ({ inherit url; } // (optionalAttrs (!isNull name) { inherit name; })) 135 | else 136 | fetchTarball attrs; 137 | 138 | # fetchurl version that is compatible between all the versions of Nix 139 | builtins_fetchurl = { url, name ? null, sha256 }@attrs: 140 | let 141 | inherit (builtins) lessThan nixVersion fetchurl; 142 | in 143 | if lessThan nixVersion "1.12" then 144 | fetchurl ({ inherit url; } // (optionalAttrs (!isNull name) { inherit name; })) 145 | else 146 | fetchurl attrs; 147 | 148 | # Create the final "sources" from the config 149 | mkSources = config: 150 | mapAttrs ( 151 | name: spec: 152 | if builtins.hasAttr "outPath" spec 153 | then abort 154 | "The values in sources.json should not have an 'outPath' attribute" 155 | else 156 | spec // { outPath = replace name (fetch config.pkgs name spec); } 157 | ) config.sources; 158 | 159 | # The "config" used by the fetchers 160 | mkConfig = 161 | { sourcesFile ? if builtins.pathExists ./sources.json then ./sources.json else null 162 | , sources ? if isNull sourcesFile then {} else builtins.fromJSON (builtins.readFile sourcesFile) 163 | , system ? builtins.currentSystem 164 | , pkgs ? mkPkgs sources system 165 | }: rec { 166 | # The sources, i.e. the attribute set of spec name to spec 167 | inherit sources; 168 | 169 | # The "pkgs" (evaluated nixpkgs) to use for e.g. non-builtin fetchers 170 | inherit pkgs; 171 | }; 172 | 173 | in 174 | mkSources (mkConfig {}) // { __functor = _: settings: mkSources (mkConfig settings); } 175 | -------------------------------------------------------------------------------- /nix/home.nix: -------------------------------------------------------------------------------- 1 | { config, lib, pkgs, ... }: 2 | 3 | with lib; 4 | 5 | let cfg = config.programs.direnv-nix-lorelei; 6 | 7 | in { 8 | options = { 9 | programs.direnv-nix-lorelei = { 10 | enable = mkOption { 11 | type = types.bool; 12 | default = false; 13 | defaultText = "false"; 14 | description = '' 15 | Whether to enable direnv-nix-lorelei. 16 | ''; 17 | }; 18 | package = mkOption { 19 | type = types.package; 20 | default = (import ./. {}).distribution.direnv-nix-lorelei; 21 | description = '' 22 | The direnv-nix-lorelei package to use. 23 | ''; 24 | }; 25 | }; 26 | }; 27 | 28 | config = mkIf cfg.enable { 29 | xdg.configFile."direnv/lib/nix-lorelei.sh".source = 30 | "${cfg.package}/share/direnv-nix-lorelei/nix-lorelei.bash"; 31 | }; 32 | } 33 | -------------------------------------------------------------------------------- /nix/remove_trace.patch: -------------------------------------------------------------------------------- 1 | diff -u a/src/logged-evaluation.nix b/src/logged-evaluation.nix 2 | --- a/src/logged-evaluation.nix 3 | +++ b/src/logged-evaluation.nix 4 | @@ -18,7 +18,7 @@ let 5 | 6 | imported = 7 | let 8 | - raw = overrides.scopedImport overrides src; 9 | + raw = import src; 10 | in 11 | if (builtins.isFunction raw) 12 | then raw {} 13 | -------------------------------------------------------------------------------- /nix/test/shell.nix: -------------------------------------------------------------------------------- 1 | let pkgs = import { config = {}; overlays = []; }; 2 | in pkgs.stdenv.mkDerivation rec { 3 | name = "direnv-nix-lorelei-testcase"; 4 | DIRENV_NIX_LORELEI = name; 5 | nativeBuildInputs = [ pkgs.hello ]; 6 | } 7 | -------------------------------------------------------------------------------- /nix/test/test.bats: -------------------------------------------------------------------------------- 1 | setup_file() 2 | { 3 | local testhome 4 | testhome="$(readlink --canonicalize "$BATS_RUN_TMPDIR/testhome")" 5 | 6 | export HOME="$testhome" 7 | export XDG_CONFIG_HOME="$testhome/.config" 8 | export XDG_DATA_HOME="$testhome/.local/share" 9 | export SRC="$testhome/src" 10 | 11 | local lib="$XDG_CONFIG_HOME/direnv/lib" 12 | 13 | mkdir --parents "$lib" "$XDG_DATA_HOME" "$SRC" 14 | cp "$LORELEI/share/direnv-nix-lorelei/nix-lorelei.bash" "$lib/nix-lorelei.sh" 15 | cp "$SHELL_NIX" "$SRC/shell.nix" 16 | echo "use_nix_gcrooted -a" > "$SRC/.envrc" 17 | 18 | direnv allow "$SRC" 19 | } 20 | 21 | @test "Lorelei PATH augmented from build inputs" { 22 | run dash -c 'direnv exec "$SRC" hello -g "_hello there_" 2>&1 | tail -1' 23 | [ "$status" -eq 0 ] 24 | [ "$output" = "_hello there_" ] 25 | } 26 | 27 | @test "Lorelei gets other environment variables too" { 28 | run dash -c 'direnv exec "$SRC" dash -c '"'"' echo "$DIRENV_NIX_LORELEI" '"'"' 2>&1 | tail -1' 29 | [ "$status" -eq 0 ] 30 | [ "$output" = "direnv-nix-lorelei-testcase" ] 31 | } 32 | 33 | @test "Lorelei watches .envrc" { 34 | run grep .envrc "$SRC/.direnv/hashes" 35 | [ "$status" -eq 0 ] 36 | } 37 | 38 | @test "Lorelei watches shell.nix" { 39 | run grep "$SRC/shell.nix" "$SRC/.direnv/hashes" 40 | [ "$status" -eq 0 ] 41 | } 42 | -------------------------------------------------------------------------------- /nix/test/test.nix: -------------------------------------------------------------------------------- 1 | { bats 2 | , coreutils 3 | , dash 4 | , direnv 5 | , direnv-nix-lorelei 6 | , gnugrep 7 | , ncurses 8 | , nix-project-lib 9 | , path 10 | }: 11 | 12 | let 13 | progName = "direnv-nix-lorelei-test"; 14 | meta.description = "Test of Lorelei"; 15 | in 16 | 17 | nix-project-lib.writeShellCheckedExe progName 18 | { 19 | inherit meta; 20 | path = [ 21 | bats 22 | coreutils 23 | dash 24 | direnv 25 | gnugrep 26 | ncurses # DESIGN: for fancy Bats output 27 | ]; 28 | } 29 | '' 30 | set -eu 31 | set -o pipefail 32 | 33 | 34 | . "${nix-project-lib.common}/share/nix-project/common.bash" 35 | 36 | 37 | NIX_EXE="$(command -v nix || true)" 38 | 39 | 40 | print_usage() 41 | { 42 | cat - <