├── .github └── workflows │ └── rust.yml ├── .gitignore ├── CHANGELOG.md ├── Cargo.toml ├── LICENSE-APACHE ├── LICENSE-MIT ├── README.md ├── examples ├── basic.rs ├── file.rs └── json │ ├── bad.json │ └── good.json └── src ├── context.rs ├── culprit.rs ├── lib.rs ├── result.rs ├── src_location.rs └── trace.rs /.github/workflows/rust.yml: -------------------------------------------------------------------------------- 1 | name: Rust 2 | 3 | on: 4 | push: 5 | branches: [ "main" ] 6 | pull_request: 7 | branches: [ "main" ] 8 | 9 | env: 10 | CARGO_TERM_COLOR: always 11 | 12 | jobs: 13 | build: 14 | 15 | runs-on: ubuntu-latest 16 | 17 | steps: 18 | - uses: actions/checkout@v4 19 | - name: Build 20 | run: cargo build --verbose 21 | - name: Run tests 22 | run: cargo test --verbose 23 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | # Generated by Cargo 2 | # will have compiled files and executables 3 | debug/ 4 | target/ 5 | 6 | # Remove Cargo.lock from gitignore if creating an executable, leave it for libraries 7 | # More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html 8 | Cargo.lock 9 | 10 | # These are backup files generated by rustfmt 11 | **/*.rs.bk 12 | 13 | # MSVC Windows builds of rustc generate these, which store debugging information 14 | *.pdb 15 | 16 | # RustRover 17 | # JetBrains specific template is maintained in a separate JetBrains.gitignore that can 18 | # be found at https://github.com/github/gitignore/blob/main/Global/JetBrains.gitignore 19 | # and can be added to the global gitignore or merged into this file. For a more nuclear 20 | # option (not recommended) you can uncomment the following to ignore the entire idea folder. 21 | #.idea/ 22 | 23 | # Added by cargo 24 | 25 | /target 26 | -------------------------------------------------------------------------------- /CHANGELOG.md: -------------------------------------------------------------------------------- 1 | # Changelog 2 | 3 | All notable changes to culprit will be documented in this file. 4 | 5 | ## [0.4.0] - 2025-03-01 6 | 7 | - Culprit derives Clone when Context derives Clone 8 | 9 | ## [0.3.0] - 2025-01-06 10 | 11 | - Rename Fingerprint to Context 12 | - Rename what used to be Context to Trace 13 | - More idiomatic naming across the board 14 | - Exported optional Result type alias 15 | 16 | ## [0.2.0] - 2025-01-01 17 | 18 | - First working release on crates.io 19 | 20 | 21 | 22 | [0.3.0]: https://github.com/carlsverre/tryiter/compare/v0.2.0...v0.3.0 23 | [0.2.0]: https://github.com/carlsverre/tryiter/compare/3c27380...v0.2.0 24 | -------------------------------------------------------------------------------- /Cargo.toml: -------------------------------------------------------------------------------- 1 | [package] 2 | name = "culprit" 3 | version = "0.4.0" 4 | edition = "2021" 5 | authors = ["Carl Sverre"] 6 | description = "A Rust error crate with the goal of identifying precisely where and in which context an error occurs." 7 | repository = "https://github.com/carlsverre/culprit" 8 | license = "MIT OR Apache-2.0" 9 | keywords = ["error", "error-handling", "result"] 10 | readme = "README.md" 11 | 12 | [dependencies] 13 | smallvec = { version = "1.14", features = ["union"] } 14 | 15 | [dev-dependencies] 16 | serde = "1.0" 17 | serde_json = "1.0" 18 | -------------------------------------------------------------------------------- /LICENSE-APACHE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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Culprit

2 |

3 | 4 | docs.rs 5 | 6 | 7 | crates.io 8 | 9 | 10 | Build Status 11 | 12 |

13 | 14 | A Rust error crate with the goal of identifying precisely where and in which context an error occurs. 15 | 16 | **Goals:** 17 | 1. Context both in the logical control flow as well as physical space in files 18 | 2. Unique public facing errors 19 | 3. Minimal error sets per function/module 20 | 4. Aligning errors to error codes for external handling (i.e. outside of rust) 21 | 22 | > [!WARNING] 23 | > Culprit is extremely-alpha and may dramatically change at any point. It's currently undergoing design and testing within some projects. Ideas and discussion is welcome during this process. 24 | 25 | **Table of Contents**: 26 | - [Getting started](#getting-started) 27 | - [Concept and comparison to other crates](#concept-and-comparison-to-other-crates) 28 | - [Outstanding Work](#outstanding-work) 29 | 30 | # Getting started 31 | 32 | **First**, define some context types which must implement Debug and Display. A Context represents the unique error cases that can occur in your app. Context types may wrap context from other abstraction layers such as modules or crates. Context types should be small and represent the most relevant context of a given error state. 33 | 34 | ```rust 35 | #[derive(Debug)] 36 | enum StorageCtx { 37 | Io(std::io::ErrorKind), 38 | Corrupt, 39 | } 40 | impl Display for StorageCtx { ... } 41 | 42 | #[derive(Debug)] 43 | enum CalcCtx { 44 | NotANumber, 45 | Storage(StorageCtx 46 | ), 47 | } 48 | impl Display for CalcCtx { ... } 49 | ``` 50 | 51 | **Next**, Implement `From` conversions to build `Contexts` from `Errors` and other `Contexts`: 52 | 53 | ```rust 54 | impl From for StorageCtx { 55 | fn from(e: std::io::Error) -> Self { 56 | StorageCtx::Io(e.kind()) 57 | } 58 | } 59 | 60 | impl From for CalcCtx { 61 | fn from(f: StorageCtx) -> Self { 62 | CalcCtx::Storage(f) 63 | } 64 | } 65 | ``` 66 | 67 | **Next**, use `Culprit` as the error type in a Result: 68 | 69 | ```rust 70 | fn read_file(file: &str) -> Result> { 71 | Ok(std::fs::read_to_string(file)?) 72 | } 73 | 74 | fn sum_file(file: &str) -> Result> { 75 | // calling `or_ctx` or `or_into_ctx` is required when the result already contains a Culprit but you want to change the context. 76 | let data = read_file(&req.file).or_into_ctx()?; 77 | ... 78 | } 79 | ``` 80 | 81 | **Finally**, check out your fancy new Culprit error message when you debug or display a Culprit: 82 | 83 | ``` 84 | Error: Calc(NotANumber) 85 | 0: not a number, at examples/file.rs:136:37 86 | 1: expected number; got String("hello"), at examples/file.rs:100:32 87 | ``` 88 | 89 | > [!NOTE] 90 | > For the full example please visit [file.rs](./examples/file.rs) 91 | 92 | # Concept and comparison to other crates 93 | 94 | Culprit came around while I was exploring various error handling patterns and crates in Rust. I roughly categorize them in the following way: 95 | 96 | 1. New Type: A new type per abstraction boundary (often an enum) often wraps the source error from lower layers directly, providing additional context via the type's `Display/Debug impl` and associated fields. Example: [thiserror] 97 | 98 | 2. Accumulator: A single type that consumes an error and then allows additional context to be attached to it as it flows up the stack. Example: [anyhow] 99 | 100 | 3. Hybrid: An Accumulator type which is generic, allowing it to be specialized with a New Type (often an enum). Provides context via the New Type as well as dynamic attachments. Example: [culprit] 101 | 102 | Each of these patterns are able to capture errors as well as the **logical trace** of an erroneous program state. 103 | 104 | 105 | > [!TIP] 106 | > I define **logical trace** as the path the error takes through a program. The path is made up of steps, which primarily correlate with an error passing between modules, crates, threads, or async tasks. The developer may add context to points on the path to further illuminate the error's path. It's important to note that while they share similar properties, a logical trace is not the same as a backtrace. The former captures the error's flow through the codebase while the latter captures the state of the stack at a particular point in time. 107 | 108 | Here is a table comparing common Rust error crates to Culprit. _Please file an issue if I made a mistake or am missing a commonly used crate._ 109 | 110 | 111 | | crate | pattern | uses unsafe | logical trace | captured context | 112 | | --------------- | ----------- | ----------- | ------------------------------- | --------------------------------------------------------------- | 113 | | [anyhow] | Accumulator | yes | context | strings, Backtrace³, custom types¹, source error¹ | 114 | | [error-stack] | Hybrid | yes | context, enriched, [SpanTrace]³ | strings, Backtrace³, [SpanTrace]³, custom types¹, source error¹ | 115 | | [eyre] | Accumulator | yes | context, [SpanTrace]³ | strings, Backtrace³, [SpanTrace]³, custom types¹, source error¹ | 116 | | [thiserror] | New Type | no | context | Backtrace²⁺³, custom types, source error | 117 | | [tracing_error] | Hybrid | yes | [SpanTrace] | only [SpanTrace] | 118 | | [culprit] | Hybrid | no | context, enriched | strings, custom types, source error | 119 | 120 | ¹ Runtime retrieval requires `TypeId` lookup
121 | ² Requires Rust nightly
122 | ³ Optional feature 123 | 124 | The first thing you may notice is that most of the error handling crates use unsafe. They do this for varying reasons, but the most common use case I found is to support dynamic extraction of nested types at runtime. Examples: [anyhow:downcast_ref] and [error-stack:downcast_ref]. This is a perfectly fine decision, however I believe it comes with some important tradeoffs. The first is crate complexity. The machinery required to store and retrieve values by type involves a lot of very tricky unsafe usage and some clever typesystem shenanigans to keep the Rust compiler happy. The second tradeoff is that it obfuscates the set of possible erroneous states by hiding that information from the typesystem. 125 | 126 | > [!NOTE] 127 | > When [error_generic_member_access] finally stabilizes, these crates may choose to eliminate some or all of their unsafe usage by switching to `Error::provide`. However it's not clear if or when this feature will land as the error working group seems to be somewhat abandoned as of January 2025. 128 | 129 | Returning to the [table], the next interesting feature is how the crate captures the error's [logical-trace]. I've summarized this with three labels: **context**, **enriched**, and **[SpanTrace]**. 130 | 131 | * **context**: The logical-trace is captured as additional context is accumulated by the error type. 132 | * **enriched**: The logical-trace is automatically enriched with file names and line numbers as context is accumulated. 133 | * **[SpanTrace]**: The current [tracing]::Span is captured and can be used later to query or print out the tree of Spans that led to the instantiation of an error. See [tracing_error] for more details. 134 | 135 | Finally, the [table] outlines the various ways context can be captured: 136 | 137 | * **strings**: Strings may be attached as context as the error propagates. 138 | * **Backtrace**: A [Backtrace] is generated when the error is captured. 139 | * **custom types**: A user defined type is attached as context. In Accumulator style crates the type is erased and may only be retrieved through runtime reflection. 140 | * **source error**: An unenriched error is captured as the "source". For example an underlying `io::Error` is stored as context as the root cause. 141 | * **[SpanTrace]**: The current [tracing]::Span is stored as context when the error is captured. 142 | 143 | With these details in mind, we can finally discuss what makes Culprit unique. Per the table, Culprit is a Hybrid between the New Type and Accumulator model. It's generic over a `Context` type which is provided by the developer. Internally, Culprit builds a [logical-trace] of physical source code locations, context changes, and notes. The combination of a dynamic [logical-trace] with a custom `Context` type provides a best-of-both-worlds experience. 144 | 145 | When using Culprit, the highest level `Context` types should represent all the erroneous states a program can be in. These higher level types will wrap lower level `Context` types all the way down to the root cause of each error state. Because Culprit automatically captures human-readable details in the [logical-trace], the `Context` types are free to only capture what the program needs to handle error states. This allows `Context` types to be closer to a pure representation of the various error states a program can be in. 146 | 147 | One of Culprit's goals is to make it easier for the developer to map erroneous states to error codes. This is useful when writing developer facing binaries or APIs. Culprit suggests that by keeping the `Context` as simple as possible, error codes can be defined as a mapping between paths through the `Context` type and a set of error codes. I accept that you can also achieve this statically with [thiserror] or dynamically via reflection in the other error libraries. However, I believe Culprit is the first crate to make this an explicit design goal and I hope to develop methods to make managing this error code mapping easier. 148 | 149 | # Outstanding Work 150 | 151 | - [x] prefix result extension fns with `or_` to be more idiomatic 152 | - [x] context fns should return `Into` 153 | - [ ] implement `#[derive(CulpritContext)]` 154 | - [ ] provides `Display` attr and impl 155 | - [ ] provides `From` impls for deriving Contexts from Errors or other Contexts. Would be nice to support mapping/extraction. 156 | - [ ] provides `Into>` impl for raising new errors 157 | - [x] rename `Fingerprint` to `Context` 158 | - [ ] add [SpanTrace] support behind a featureflag 159 | - [x] add `type Result = Result>` 160 | - [ ] `bail!` or similar macro for easy error generation 161 | - [ ] document all methods and modules 162 | 163 | [table]: #comparison-table 164 | [logical-trace]: #logical-trace 165 | 166 | [anyhow]:https://docs.rs/anyhow/latest/anyhow/ 167 | [error-stack]: https://docs.rs/error-stack/0.5.0/error_stack/ 168 | [eyre]: https://docs.rs/eyre/latest/eyre/ 169 | [thiserror]:https://docs.rs/thiserror/latest/thiserror/ 170 | [tracing_error]: https://docs.rs/tracing-error/latest/tracing_error/ 171 | [culprit]: https://docs.rs/culprit/latest/culprit/ 172 | [SpanTrace]: https://docs.rs/tracing-error/latest/tracing_error/struct.SpanTrace.html 173 | [anyhow:downcast_ref]: https://docs.rs/anyhow/1.0.95/anyhow/struct.Error.html#method.downcast_ref 174 | [error-stack:downcast_ref]: https://docs.rs/error-stack/0.5.0/error_stack/struct.Report.html 175 | [error_generic_member_access]: https://github.com/rust-lang/rust/issues/99301 176 | [tracing]: https://docs.rs/tracing/latest/tracing/index.html 177 | [Backtrace]: https://doc.rust-lang.org/std/backtrace/index.html -------------------------------------------------------------------------------- /examples/basic.rs: -------------------------------------------------------------------------------- 1 | use std::{error::Error, fmt::Display}; 2 | 3 | use culprit::{Culprit, ResultExt}; 4 | 5 | #[derive(Debug)] 6 | struct SimpleError; 7 | impl Error for SimpleError {} 8 | impl Display for SimpleError { 9 | fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { 10 | write!(f, "SimpleError") 11 | } 12 | } 13 | 14 | #[derive(Debug)] 15 | enum Context { 16 | A, 17 | } 18 | 19 | impl Display for Context { 20 | fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { 21 | write!(f, "Context::A") 22 | } 23 | } 24 | 25 | impl From for Context { 26 | fn from(_: SimpleError) -> Self { 27 | Context::A 28 | } 29 | } 30 | 31 | #[derive(Debug)] 32 | enum Context2 { 33 | Wrapped(Context), 34 | } 35 | 36 | impl Display for Context2 { 37 | fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { 38 | match self { 39 | Context2::Wrapped(x) => write!(f, "Context2::Wrapped({x})"), 40 | } 41 | } 42 | } 43 | 44 | impl From for Context2 { 45 | fn from(_: Context) -> Self { 46 | Context2::Wrapped(Context::A) 47 | } 48 | } 49 | 50 | fn raise_simple_error() -> Result<(), SimpleError> { 51 | Err(SimpleError) 52 | } 53 | 54 | fn wrap_in_culprit() -> Result<(), Culprit> { 55 | raise_simple_error()?; 56 | Ok(()) 57 | } 58 | 59 | fn map_context() -> Result<(), Culprit> { 60 | wrap_in_culprit().or_into_ctx()?; 61 | Ok(()) 62 | } 63 | 64 | fn add_note() -> Result<(), Culprit> { 65 | map_context().or_into_culprit("This is a note")?; 66 | Ok(()) 67 | } 68 | 69 | fn map_context_without_changing() -> Result<(), Culprit> { 70 | add_note().or_into_ctx()?; 71 | Ok(()) 72 | } 73 | 74 | pub fn main() { 75 | let culprit = map_context_without_changing().unwrap_err(); 76 | println!("{:?}", culprit); 77 | 78 | assert!(matches!(culprit.ctx(), &Context2::Wrapped(Context::A))); 79 | let context = culprit.trace(); 80 | assert_eq!(context.len(), 4); 81 | } 82 | -------------------------------------------------------------------------------- /examples/file.rs: -------------------------------------------------------------------------------- 1 | //! A simple example program which parses a file as a JSON array and then sums 2 | //! the values. All errors are handled by Culprit. 3 | //! 4 | //! This program is overengineered on purpose to demonstrate multiple 5 | //! abstraction layers and showcase more of Culprit's functionality. 6 | //! 7 | //! Here are some example invocations: 8 | //! 9 | //! ```sh 10 | //! # missing an argument 11 | //! cargo run --example file 12 | //! 13 | //! # missing file 14 | //! cargo run --example file missing.json 15 | //! 16 | //! # bad JSON array contents 17 | //! cargo run --example file examples/json/bad.json 18 | //! 19 | //! # good JSON array contents 20 | //! cargo run --example file examples/json/good.json 21 | //! ``` 22 | 23 | use culprit::{Culprit, ResultExt}; 24 | 25 | mod file { 26 | use culprit::{Culprit, ResultExt}; 27 | use std::{ 28 | fmt::{Display, Formatter}, 29 | path::Path, 30 | }; 31 | 32 | #[derive(Debug)] 33 | pub enum FileCtx { 34 | Io(std::io::ErrorKind), 35 | Corrupt, 36 | } 37 | 38 | impl Display for FileCtx { 39 | fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result { 40 | match self { 41 | FileCtx::Io(kind) => write!(f, "I/O error: {}", kind), 42 | FileCtx::Corrupt => write!(f, "corrupt data"), 43 | } 44 | } 45 | } 46 | 47 | impl From for FileCtx { 48 | fn from(err: std::io::Error) -> Self { 49 | FileCtx::Io(err.kind()) 50 | } 51 | } 52 | 53 | pub fn read_file>(path: P) -> Result, Culprit> { 54 | let file = std::fs::File::open(&path)?; 55 | let reader = std::io::BufReader::new(file); 56 | let data = serde_json::from_reader(reader).or_ctx(|_| FileCtx::Corrupt)?; 57 | Ok(data) 58 | } 59 | } 60 | 61 | mod calc { 62 | use crate::file; 63 | use culprit::{Culprit, ResultExt}; 64 | use std::path::Path; 65 | 66 | #[derive(Debug)] 67 | pub enum CalcCtx { 68 | NotANumber, 69 | File(file::FileCtx), 70 | } 71 | 72 | impl std::fmt::Display for CalcCtx { 73 | fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { 74 | match self { 75 | CalcCtx::NotANumber => write!(f, "not a number"), 76 | CalcCtx::File(fp) => write!(f, "{}", fp), 77 | } 78 | } 79 | } 80 | 81 | impl From for CalcCtx { 82 | fn from(fp: file::FileCtx) -> Self { 83 | CalcCtx::File(fp) 84 | } 85 | } 86 | 87 | pub fn sum_file>(path: P) -> Result> { 88 | let data = file::read_file(&path).or_into_ctx()?; 89 | let mut sum = 0f64; 90 | for value in data { 91 | match value { 92 | serde_json::Value::Number(n) => { 93 | sum += n 94 | .as_f64() 95 | .ok_or_else(|| Culprit::new(CalcCtx::NotANumber))? 96 | } 97 | other => { 98 | return Err(Culprit::new_with_note( 99 | CalcCtx::NotANumber, 100 | format!("expected number; got {:?}", other), 101 | )) 102 | } 103 | } 104 | } 105 | Ok(sum) 106 | } 107 | } 108 | 109 | #[derive(Debug)] 110 | pub enum Ctx { 111 | Calc(calc::CalcCtx), 112 | Usage, 113 | } 114 | 115 | impl std::fmt::Display for Ctx { 116 | fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { 117 | match self { 118 | Ctx::Calc(fp) => write!(f, "{}", fp), 119 | Ctx::Usage => write!(f, "usage error; expected one argument"), 120 | } 121 | } 122 | } 123 | 124 | impl From for Ctx { 125 | fn from(fp: calc::CalcCtx) -> Self { 126 | Ctx::Calc(fp) 127 | } 128 | } 129 | 130 | pub fn main() -> Result<(), Culprit> { 131 | let path = std::env::args() 132 | .nth(1) 133 | .ok_or_else(|| Culprit::new(Ctx::Usage))?; 134 | let sum = calc::sum_file(&path).or_into_ctx()?; 135 | println!("Sum: {}", sum); 136 | Ok(()) 137 | } 138 | -------------------------------------------------------------------------------- /examples/json/bad.json: -------------------------------------------------------------------------------- 1 | [ 2 | 1, 3 | "hello", 4 | 3.5 5 | ] -------------------------------------------------------------------------------- /examples/json/good.json: -------------------------------------------------------------------------------- 1 | [ 2 | 1, 3 | 2, 4 | 3.5 5 | ] -------------------------------------------------------------------------------- /src/context.rs: -------------------------------------------------------------------------------- 1 | use core::fmt::Debug; 2 | use core::fmt::Display; 3 | 4 | pub trait Context: Display + Debug + Send + Sync + 'static {} 5 | 6 | impl Context for T {} 7 | -------------------------------------------------------------------------------- /src/culprit.rs: -------------------------------------------------------------------------------- 1 | use alloc::borrow::Cow; 2 | use alloc::string::ToString; 3 | use core::{ 4 | error::Error, 5 | fmt::{Debug, Display, Formatter}, 6 | }; 7 | 8 | use crate::{ 9 | context::Context, 10 | trace::{Trace, TracePoint}, 11 | }; 12 | 13 | #[derive(Clone)] 14 | pub struct Culprit { 15 | ctx: C, 16 | stack: Trace, 17 | } 18 | 19 | impl Culprit { 20 | #[inline] 21 | #[track_caller] 22 | pub fn new(ctx: C) -> Self { 23 | let stack = Trace::from_ctx(TracePoint::new(ctx.to_string())); 24 | Self { ctx, stack } 25 | } 26 | 27 | #[inline] 28 | #[track_caller] 29 | pub fn new_with_note>>(ctx: C, note: N) -> Self { 30 | let stack = Trace::from_ctx(TracePoint::new(note)); 31 | Self { ctx, stack } 32 | } 33 | 34 | #[inline] 35 | pub fn new_with_stack(ctx: impl Into, stack: Trace) -> Self { 36 | Self { 37 | ctx: ctx.into(), 38 | stack, 39 | } 40 | } 41 | 42 | #[inline] 43 | #[track_caller] 44 | pub fn from_err>(err: E) -> Self { 45 | let stack = Trace::from_err(&err); 46 | let ctx = err.into(); 47 | Self { ctx, stack } 48 | } 49 | 50 | #[inline] 51 | #[track_caller] 52 | pub fn with_note>>(mut self, note: I) -> Self { 53 | self.stack.push(TracePoint::new(note)); 54 | self 55 | } 56 | 57 | #[inline] 58 | #[track_caller] 59 | pub fn map_ctx(self, map: F) -> Culprit 60 | where 61 | C2: Context + From, 62 | F: FnOnce(C) -> I, 63 | { 64 | Culprit { 65 | ctx: map(self.ctx).into(), 66 | stack: self.stack, 67 | } 68 | } 69 | 70 | #[inline] 71 | pub fn ctx(&self) -> &C { 72 | &self.ctx 73 | } 74 | 75 | #[inline] 76 | pub fn trace(&self) -> &Trace { 77 | &self.stack 78 | } 79 | 80 | #[inline] 81 | pub fn into_err(self) -> CulpritErr { 82 | CulpritErr(self) 83 | } 84 | } 85 | 86 | impl> From for Culprit { 87 | #[inline] 88 | #[track_caller] 89 | fn from(source: E) -> Self { 90 | Self::from_err(source) 91 | } 92 | } 93 | 94 | impl From> for (C, Trace) { 95 | #[inline] 96 | fn from(culprit: Culprit) -> Self { 97 | (culprit.ctx, culprit.stack) 98 | } 99 | } 100 | 101 | impl Debug for Culprit { 102 | fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result { 103 | write!(f, "{:?}\n{}", self.ctx, self.stack)?; 104 | Ok(()) 105 | } 106 | } 107 | 108 | impl Display for Culprit { 109 | fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result { 110 | write!(f, "{}\n{}", self.ctx, self.stack)?; 111 | Ok(()) 112 | } 113 | } 114 | 115 | pub struct CulpritErr(Culprit); 116 | 117 | impl CulpritErr { 118 | #[inline] 119 | pub fn into_culprit(self) -> Culprit { 120 | self.0 121 | } 122 | } 123 | 124 | impl Display for CulpritErr { 125 | fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result { 126 | Display::fmt(&self.0, f) 127 | } 128 | } 129 | 130 | impl Debug for CulpritErr { 131 | fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result { 132 | Debug::fmt(&self.0, f) 133 | } 134 | } 135 | 136 | impl Error for CulpritErr {} 137 | 138 | #[cfg(test)] 139 | mod tests { 140 | use core::error::Error; 141 | use core::fmt::Display; 142 | 143 | use super::Culprit; 144 | 145 | #[derive(Debug, Clone)] 146 | struct Ctx; 147 | 148 | impl Display for Ctx { 149 | fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { 150 | write!(f, "Ctx") 151 | } 152 | } 153 | 154 | impl Error for Ctx {} 155 | 156 | #[test] 157 | fn test_clone() { 158 | let culprit = Culprit::new(Ctx); 159 | let _ = culprit.clone(); 160 | } 161 | } 162 | -------------------------------------------------------------------------------- /src/lib.rs: -------------------------------------------------------------------------------- 1 | #![cfg_attr(not(test), no_std)] 2 | #![forbid(unsafe_code)] 3 | 4 | extern crate alloc; 5 | 6 | mod context; 7 | mod culprit; 8 | mod result; 9 | mod src_location; 10 | mod trace; 11 | 12 | pub use context::Context; 13 | pub use culprit::{Culprit, CulpritErr}; 14 | pub use result::ResultExt; 15 | pub use trace::TracePoint; 16 | 17 | pub type Result = core::result::Result>; 18 | -------------------------------------------------------------------------------- /src/result.rs: -------------------------------------------------------------------------------- 1 | use alloc::borrow::Cow; 2 | use alloc::string::ToString; 3 | use core::error::Error; 4 | 5 | use crate::{context::Context, culprit::Culprit, trace::Trace}; 6 | 7 | pub trait ResultExt { 8 | type Ok; 9 | type Residual; 10 | 11 | #[track_caller] 12 | fn or_ctx(self, op: F) -> Result> 13 | where 14 | F: FnOnce(Self::Residual) -> I, 15 | C: Context + From; 16 | 17 | #[inline] 18 | #[track_caller] 19 | fn or_into_ctx(self) -> Result> 20 | where 21 | Self: Sized, 22 | C: Context + From, 23 | { 24 | self.or_ctx(C::from) 25 | } 26 | 27 | #[inline] 28 | #[track_caller] 29 | fn or_culprit(self, note: N, op: F) -> Result> 30 | where 31 | N: Into>, 32 | F: FnOnce(Self::Residual) -> I, 33 | C: Context + From, 34 | Self: Sized, 35 | { 36 | self.or_ctx(op).map_err(|culprit| culprit.with_note(note)) 37 | } 38 | 39 | #[inline] 40 | #[track_caller] 41 | fn or_into_culprit(self, note: N) -> Result> 42 | where 43 | Self: Sized, 44 | C: Context + From, 45 | N: Into>, 46 | { 47 | self.or_culprit(note, C::from) 48 | } 49 | } 50 | 51 | impl ResultExt for core::result::Result { 52 | type Ok = Ok; 53 | type Residual = Err; 54 | 55 | #[track_caller] 56 | fn or_ctx(self, op: F) -> Result> 57 | where 58 | F: FnOnce(Err) -> I, 59 | C: Context + From, 60 | { 61 | match self { 62 | Ok(t) => Ok(t), 63 | Err(e) => { 64 | let stack = Trace::from_err(&e); 65 | Err(Culprit::new_with_stack(op(e), stack)) 66 | } 67 | } 68 | } 69 | } 70 | 71 | impl ResultExt for core::result::Result> { 72 | type Ok = Ok; 73 | type Residual = C1; 74 | 75 | #[track_caller] 76 | fn or_ctx(self, op: F) -> Result> 77 | where 78 | F: FnOnce(C1) -> I, 79 | C2: Context + From, 80 | { 81 | match self { 82 | Ok(t) => Ok(t), 83 | Err(culprit) => { 84 | let note = culprit.ctx().to_string(); 85 | Err(culprit.map_ctx(op).with_note(note)) 86 | } 87 | } 88 | } 89 | 90 | fn or_culprit(self, note: N, op: F) -> Result> 91 | where 92 | N: Into>, 93 | F: FnOnce(C1) -> I, 94 | Self: Sized, 95 | C2: Context + From, 96 | { 97 | match self { 98 | Ok(t) => Ok(t), 99 | Err(culprit) => Err(culprit.map_ctx(op).with_note(note)), 100 | } 101 | } 102 | 103 | fn or_into_culprit(self, note: N) -> Result> 104 | where 105 | Self: Sized, 106 | C2: Context + From, 107 | N: Into>, 108 | { 109 | match self { 110 | Ok(t) => Ok(t), 111 | Err(culprit) => Err(culprit.map_ctx(C2::from).with_note(note)), 112 | } 113 | } 114 | } 115 | -------------------------------------------------------------------------------- /src/src_location.rs: -------------------------------------------------------------------------------- 1 | use core::{ 2 | fmt::{Debug, Display, Formatter, Result}, 3 | panic::Location, 4 | }; 5 | 6 | #[derive(Copy, Clone, Eq, Hash, Ord, PartialEq, PartialOrd)] 7 | pub struct SrcLocation(&'static Location<'static>); 8 | 9 | impl SrcLocation { 10 | #[inline] 11 | #[track_caller] 12 | pub fn new() -> Self { 13 | Self(Location::caller()) 14 | } 15 | 16 | #[inline] 17 | pub fn file(&self) -> &'static str { 18 | self.0.file() 19 | } 20 | 21 | #[inline] 22 | pub fn line(&self) -> u32 { 23 | self.0.line() 24 | } 25 | 26 | #[inline] 27 | pub fn column(&self) -> u32 { 28 | self.0.column() 29 | } 30 | } 31 | 32 | impl From for &'static Location<'static> { 33 | #[inline] 34 | fn from(val: SrcLocation) -> Self { 35 | val.0 36 | } 37 | } 38 | 39 | impl Default for SrcLocation { 40 | #[inline] 41 | #[track_caller] 42 | fn default() -> Self { 43 | Self::new() 44 | } 45 | } 46 | 47 | impl Debug for SrcLocation { 48 | #[inline] 49 | fn fmt(&self, f: &mut Formatter<'_>) -> Result { 50 | f.debug_struct("StaticLocation") 51 | .field("file", &self.0.file()) 52 | .field("line", &self.0.line()) 53 | .field("column", &self.0.column()) 54 | .finish() 55 | } 56 | } 57 | 58 | impl Display for SrcLocation { 59 | #[inline] 60 | fn fmt(&self, f: &mut Formatter<'_>) -> Result { 61 | Display::fmt(&self.0, f) 62 | } 63 | } 64 | -------------------------------------------------------------------------------- /src/trace.rs: -------------------------------------------------------------------------------- 1 | use alloc::borrow::Cow; 2 | use alloc::string::ToString; 3 | use alloc::vec::Vec; 4 | use core::error::Error; 5 | use core::fmt::{Display, Formatter}; 6 | use smallvec::SmallVec; 7 | 8 | use crate::src_location::SrcLocation; 9 | 10 | #[derive(Clone)] 11 | pub struct TracePoint { 12 | location: Option, 13 | note: Cow<'static, str>, 14 | } 15 | 16 | impl TracePoint { 17 | #[track_caller] 18 | pub fn new>>(note: N) -> Self { 19 | Self { 20 | location: Some(SrcLocation::new()), 21 | note: note.into(), 22 | } 23 | } 24 | 25 | pub(crate) fn from_err_source(e: E) -> Self { 26 | Self { 27 | location: None, 28 | note: e.to_string().into(), 29 | } 30 | } 31 | } 32 | 33 | impl Display for TracePoint { 34 | fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result { 35 | let note = &self.note; 36 | match &self.location { 37 | None => write!(f, "{note}")?, 38 | Some(loc) => write!(f, "{note}, at {loc}")?, 39 | } 40 | Ok(()) 41 | } 42 | } 43 | 44 | #[derive(Default, Clone)] 45 | pub struct Trace(SmallVec<[TracePoint; 1]>); 46 | 47 | impl Trace { 48 | pub fn from_ctx(ctx: TracePoint) -> Self { 49 | Self(SmallVec::from_buf([ctx])) 50 | } 51 | 52 | #[track_caller] 53 | pub fn from_err(err: &E) -> Self { 54 | let ctx = TracePoint::new(err.to_string()); 55 | if err.source().is_none() { 56 | // fast path if there is no source 57 | return Self(SmallVec::from_buf([ctx])); 58 | } 59 | 60 | let mut stack = Vec::new(); 61 | stack.push(ctx); 62 | 63 | // add all error sources to the trace 64 | let mut source = err.source(); 65 | while let Some(err) = source { 66 | stack.push(TracePoint::from_err_source(err)); 67 | source = err.source(); 68 | } 69 | 70 | // reverse the stack so the the error is at the top 71 | stack.reverse(); 72 | 73 | Self(SmallVec::from_vec(stack)) 74 | } 75 | 76 | #[inline] 77 | pub fn push(&mut self, ctx: TracePoint) { 78 | self.0.push(ctx); 79 | } 80 | 81 | /// iterate over the trace from the top of the stack to the bottom 82 | #[inline] 83 | pub fn iter(&self) -> impl DoubleEndedIterator { 84 | self.0.iter().rev() 85 | } 86 | 87 | #[inline] 88 | pub fn len(&self) -> usize { 89 | self.0.len() 90 | } 91 | 92 | #[inline] 93 | pub fn is_empty(&self) -> bool { 94 | self.0.is_empty() 95 | } 96 | } 97 | 98 | impl Display for Trace { 99 | fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result { 100 | for (i, ctx) in self.iter().enumerate() { 101 | if i > 0 { 102 | writeln!(f)?; 103 | } 104 | write!(f, "{i}: {ctx}")?; 105 | } 106 | Ok(()) 107 | } 108 | } 109 | --------------------------------------------------------------------------------