├── .gitignore
├── .npmignore
├── .vscode
    └── settings.json
├── CHANGES.md
├── README.md
├── etc
    ├── eslint.mts
    ├── logo.ai
    ├── logo.png
    ├── logo.svg
    ├── nps.yaml
    ├── tsc.json
    └── vite.mts
├── package.json
├── src
    ├── traits.spec.ts
    └── traits.ts
└── tsconfig.json


/.gitignore:
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1 | dst
2 | node_modules
3 | 


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/.npmignore:
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1 | node_modules
2 | dst/traits.spec.*
3 | dst/traits.js
4 | 


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/.vscode/settings.json:
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1 | {
2 |     "typescript.tsdk": "./node_modules/typescript/lib"
3 | }
4 | 


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/CHANGES.md:
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 1 | 
 2 | CHANGES
 3 | =======
 4 | 
 5 | 1.1.3 (2023-05-31)
 6 | ------------------
 7 | 
 8 | - UPDATE: update package dependencies
 9 | - CLEANUP: cleanup Vite configuration
10 | 
11 | 1.1.2 (2023-05-06)
12 | ------------------
13 | 
14 | - UPDATE: update package dependencies
15 | 
16 | 1.1.1 (2023-04-06)
17 | ------------------
18 | 
19 | - UPDATE: update package dependencies
20 | 
21 | 1.1.0 (2023-03-08)
22 | ------------------
23 | 
24 | - IMPROVEMENT: add support to derive() for a single trailing regular class
25 | 
26 | 1.0.9 (2023-03-07)
27 | ------------------
28 | 
29 | - CLEANUP: improve test suite
30 | - CLEANUP: improve project description
31 | 
32 | 1.0.8 (2023-03-07)
33 | ------------------
34 | 
35 | - CLEANUP: remove obsolete entries from package.json
36 | 
37 | 1.0.7 (2023-03-06)
38 | ------------------
39 | 
40 | - CLEANUP: improve test suite
41 | - CLEANUP: improve project description
42 | 
43 | 1.0.6 (2023-03-06)
44 | ------------------
45 | 
46 | - CLEANUP: improve test suite
47 | - CLEANUP: improve project description
48 | 
49 | 1.0.5 (2023-03-06)
50 | ------------------
51 | 
52 | - CLEANUP: improve project description
53 | 
54 | 1.0.3 (2023-03-06)
55 | ------------------
56 | 
57 | - REFACTORING: switch to new @traits-ts namespacing
58 | 
59 | 1.0.2 (2023-02-26)
60 | ------------------
61 | 
62 | - UPDATE: update package dependencies
63 | 
64 | 1.0.1 (2023-02-22)
65 | ------------------
66 | 
67 | - BUGFIX: fix constructor parameter merging
68 | - UPDATE: update package dependencies
69 | 
70 | 1.0.0 (2023-01-26)
71 | ------------------
72 | 
73 | (first stable release)
74 | 
75 | 


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/README.md:
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  1 | 
  2 | <img src="https://raw.githubusercontent.com/traits-ts/core/refs/heads/master/etc/logo.svg" width="200" style="float: right" align="right" alt=""/>
  3 | 
  4 | @traits-ts/core
  5 | ===============
  6 | 
  7 | **Traits for TypeScript Classes (Core)**
  8 | 
  9 | <p/>
 10 | <a href="https://traits-ts.org">Project Home</a> |
 11 | <a href="https://github.com/traits-ts/core">Github Repository</a> |
 12 | <a href="https://npmjs.com/@traits-ts/core">NPM Distribution</a>
 13 | 
 14 | <p/>
 15 | <img src="https://nodei.co/npm/@traits-ts/core.png?downloads=true&stars=true" alt=""/>
 16 | 
 17 | [![github (author stars)](https://img.shields.io/github/stars/rse?logo=github&label=author%20stars&color=%233377aa)](https://github.com/rse)
 18 | [![github (author followers)](https://img.shields.io/github/followers/rse?label=author%20followers&logo=github&color=%234477aa)](https://github.com/rse)
 19 | <br/>
 20 | [![npm (project release)](https://img.shields.io/npm/v/@traits-ts/core?logo=npm&label=npm%20release&color=%23cc3333)](https://npmjs.com/@traits-ts/core)
 21 | [![npm (project downloads)](https://img.shields.io/npm/dm/@traits-ts/core?logo=npm&label=npm%20downloads&color=%23cc3333)](https://npmjs.com/@traits-ts/core)
 22 | 
 23 | About
 24 | -----
 25 | 
 26 | This is a TypeScript library providing a *trait* (aka *mixin*)
 27 | facility for extending classes with *multiple* base functionalities,
 28 | although TypeScript/JavaScript technically do not allow multiple
 29 | inheritance.
 30 | 
 31 | For this, it internally leverages the regular `class extends` mechanism
 32 | and "linearizes" the trait hierarchy at the JavaScript level, so it
 33 | is does not have to manipulate the run-time objects at all. At the
 34 | TypeScript level, it is fully type-safe and recursively derives all
 35 | properties of the traits a class is derived from.
 36 | 
 37 | This library consists of just three API functions: `trait` for defining
 38 | a trait (or sub-trait), the API function `derive` for deriving a base
 39 | class from one or more defined traits, and the API type-guard function
 40 | `derived` to ensure an object has the functionality of a trait under
 41 | run-time.
 42 | 
 43 | See also [@traits-ts/stdlib](https://github.com/traits-ts/stdlib) for
 44 | a companion library of standard, reusable, generic, typed traits (aka mixins),
 45 | based on this base library. Currently, this standard library consists
 46 | of the reusable traits *Identifiable*, *Configurable*, *Bindable*,
 47 | *Subscribable*, *Hookable*, *Finalizable*, *Traceable*, and
 48 | *Serializable*.
 49 | 
 50 | Installation
 51 | ------------
 52 | 
 53 | ```sh
 54 | $ npm install --save @traits-ts/core
 55 | ```
 56 | 
 57 | API
 58 | ---
 59 | 
 60 | The Application Programming Interface (API) of **@traits-ts/core** consists
 61 | of just three API functions and can be used in the following way:
 62 | 
 63 | ```ts
 64 | //  Import API functions.
 65 | import { trait, derive, derived } from "@traits-ts/core"
 66 | //       =====  ======  =======
 67 | 
 68 | //  Define regular trait Foo.
 69 | const Foo = trait((base) => class Foo extends base { ... })
 70 | //          =====================     ============
 71 | 
 72 | //  Define regular sub-trait Foo, inheriting from super-traits Bar and Qux.
 73 | const Foo = trait([ Bar, Qux ], (base) => class Foo extends base { ... })
 74 | //                ============
 75 | 
 76 | //  Define generic trait Foo.
 77 | const Foo = <T>() => trait((base) => class Foo extends base { ... <T> ... })
 78 | //          =====                                                 ===
 79 | 
 80 | //  Define generic sub-trait Foo, inheriting from super-traits Bar and Qux.
 81 | const Foo = <T>() => trait([ Bar, Qux<T> ], (base) => class Foo extends base { ... <T> ... })
 82 | //          =====          ===============                                         ===
 83 | 
 84 | //  Define application class with features derived from traits Foo, Bar and Qux.
 85 | class Sample extends derive(Foo, Bar<Baz>, Qux) { ... }
 86 | //                   ==========================
 87 | 
 88 | //  Define application class with features derived from traits and a trailing regular class
 89 | class Sample extends derive(Foo, Bar<Baz>, Qux, EventEmitter) { ... }
 90 | //                                              ============
 91 | 
 92 | //  Call super constructor from application class constructor.
 93 | class Sample extends derive(...) { constructor () { super(); ... } ... }
 94 | //                                                  =======
 95 | 
 96 | //  Call super method from application class method.
 97 | class Sample extends derive(...) { foo () { ...; super.foo(...); ... } ... }
 98 | //                                               ==============
 99 | 
100 | //  Check whether application class is derived from a trait.
101 | const sample = new Sample(); if (derived(sample, Foo)) ...
102 | //                               ====================
103 | ```
104 | 
105 | Examples
106 | -------
107 | 
108 | ### Regular, Orthogonal/Independent Traits
109 | 
110 | ```ts
111 | import { trait, derive } from "@traits-ts/core"
112 | 
113 | const Duck = trait((base) => class extends base {
114 |     squeak () { return "squeak" }
115 | })
116 | const Parrot = trait((base) => class extends base {
117 |     talk () { return "talk" }
118 | })
119 | const Animal = class Animal extends derive(Duck, Parrot) {
120 |     walk () { return "walk" }
121 | }
122 | 
123 | const animal = new Animal()
124 | 
125 | animal.squeak() // -> "squeak"
126 | animal.talk()   // -> "talk"
127 | animal.walk()   // -> "walk"
128 | ```
129 | 
130 | ### Regular, Bounded/Dependent Traits
131 | 
132 | ```ts
133 | import { trait, derive } from "@traits-ts/core"
134 | 
135 | const Queue = trait((base) => class extends base {
136 |     private buf: Array<number> = []
137 |     get () { return this.buf.pop() }
138 |     put (x: number) { this.buf.unshift(x) }
139 | })
140 | const Doubling = trait([ Queue ], (base) => class extends base {
141 |     put (x: number) { super.put(2 * x) }
142 | })
143 | const Incrementing = trait([ Queue ], (base) => class extends base {
144 |     put (x: number) { super.put(x + 1) }
145 | })
146 | const Filtering = trait([ Queue ], (base) => class extends base {
147 |     put (x: number) { if (x >= 0) super.put(x) }
148 | })
149 | 
150 | const MyQueue = class MyQueue extends
151 |     derive(Filtering, Doubling, Incrementing, Queue) {}
152 | 
153 | const queue = new MyQueue()
154 | 
155 | queue.get()    // -> undefined
156 | queue.put(-1)
157 | queue.get()    // -> undefined
158 | queue.put(1)
159 | queue.get()    // -> 3
160 | queue.put(10)
161 | queue.get()    // -> 21
162 | ```
163 | 
164 | ### Generic, Bounded/Dependent Traits
165 | 
166 | ```ts
167 | import { trait, derive } from "@traits-ts/core"
168 | 
169 | const Queue = <T>() => trait((base) => class extends base {
170 |     private buf: Array<T> = []
171 |     get ()     { return this.buf.pop() }
172 |     put (x: T) { this.buf.unshift(x) }
173 | })
174 | const Tracing = <T>() => trait([ Queue<T> ], (base) => class extends base {
175 |     private trace (ev: string, x?: T) { console.log(ev, x) }
176 |     get ()     { const x = super.get(); this.trace("get", x); return x }
177 |     put (x: T) { this.trace("put", x); super.put(x) }
178 | })
179 | 
180 | const MyTracingQueue = class MyTracingQueue extends
181 |     derive(Tracing<string>, Queue<string>) {}
182 | 
183 | const queue = new MyTracingQueue()
184 | 
185 | queue.put("foo")  // -> console: put foo
186 | queue.get()       // -> console: get foo
187 | queue.put("bar")  // -> console: put bar
188 | queue.put("qux")  // -> console: put qux
189 | queue.get()       // -> console: get bar
190 | queue.get()       // -> console: get qux
191 | ```
192 | 
193 | History
194 | -------
195 | 
196 | The **@traits-ts/core** library was developed in January 2025 by Dr. Ralf
197 | S. Engelschall. It is heavily inspired by Scala traits and the API
198 | of **@ddd-ts/traits**, although **@traits-ts/core** is a "from scratch"
199 | implementation for TypeScript.
200 | 
201 | Support
202 | -------
203 | 
204 | The work on this Open Source Software was financially supported by the
205 | german non-profit organisation *SEA Software Engineering Academy gGmbH*.
206 | 
207 | License
208 | -------
209 | 
210 | Copyright &copy; 2025 Dr. Ralf S. Engelschall (http://engelschall.com/)
211 | 
212 | Permission is hereby granted, free of charge, to any person obtaining
213 | a copy of this software and associated documentation files (the
214 | "Software"), to deal in the Software without restriction, including
215 | without limitation the rights to use, copy, modify, merge, publish,
216 | distribute, sublicense, and/or sell copies of the Software, and to
217 | permit persons to whom the Software is furnished to do so, subject to
218 | the following conditions:
219 | 
220 | The above copyright notice and this permission notice shall be included
221 | in all copies or substantial portions of the Software.
222 | 
223 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
224 | EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
225 | MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
226 | IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
227 | CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
228 | TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
229 | SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
230 | 
231 | 


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/etc/eslint.mts:
--------------------------------------------------------------------------------
 1 | /*
 2 | **  @rse/traits - Traits for TypeScript Classes
 3 | **  Copyright (c) 2025 Dr. Ralf S. Engelschall <rse@engelschall.com>
 4 | **  Licensed under MIT license <https://spdx.org/licenses/MIT>
 5 | */
 6 | 
 7 | import pluginJs      from "@eslint/js"
 8 | import pluginStd     from "neostandard"
 9 | import pluginN       from "eslint-plugin-n"
10 | import pluginImport  from "eslint-plugin-import"
11 | import pluginPromise from "eslint-plugin-promise"
12 | import pluginMocha   from "eslint-plugin-mocha"
13 | import pluginChai    from "eslint-plugin-chai-expect"
14 | import pluginTS      from "typescript-eslint"
15 | import globals       from "globals"
16 | import parserTS      from "@typescript-eslint/parser"
17 | 
18 | export default [
19 |     pluginJs.configs.recommended,
20 |     pluginMocha.configs.recommended,
21 |     pluginChai.configs["recommended-flat"],
22 |     ...pluginTS.configs.strict,
23 |     ...pluginTS.configs.stylistic,
24 |     ...pluginStd({
25 |         ignores: pluginStd.resolveIgnoresFromGitignore()
26 |     }),
27 |     {
28 |         plugins: {
29 |             "n":       pluginN,
30 |             "import":  pluginImport,
31 |             "promise": pluginPromise
32 |         },
33 |         files: [ "src/**/*.ts" ],
34 |         languageOptions: {
35 |             ecmaVersion: 2022,
36 |             sourceType:  "module",
37 |             parser: parserTS,
38 |             parserOptions: {
39 |                 ecmaFeatures: {
40 |                     jsx: false
41 |                 }
42 |             },
43 |             globals: {
44 |                 ...globals.node,
45 |                 ...globals.browser,
46 |                 ...globals.commonjs
47 |             }
48 |         },
49 |         rules: {
50 |             "curly":                                              "off",
51 |             "require-atomic-updates":                             "off",
52 |             "dot-notation":                                       "off",
53 |             "no-labels":                                          "off",
54 |             "no-useless-constructor":                             "off",
55 |             "no-unused-vars":                                     "off",
56 | 
57 |             "@stylistic/indent":                                  [ "error", 4, { SwitchCase: 1 } ],
58 |             "@stylistic/linebreak-style":                         [ "error", "unix" ],
59 |             "@stylistic/semi":                                    [ "error", "never" ],
60 |             "@stylistic/operator-linebreak":                      [ "error", "after", { overrides: { "&&": "before", "||": "before", ":": "after" } } ],
61 |             "@stylistic/brace-style":                             [ "error", "stroustrup", { allowSingleLine: true } ],
62 |             "@stylistic/quotes":                                  [ "error", "double" ],
63 | 
64 |             "@stylistic/no-multi-spaces":                         "off",
65 |             "@stylistic/no-multi-spaces":                         "off",
66 |             "@stylistic/no-multiple-empty-lines":                 "off",
67 |             "@stylistic/key-spacing":                             "off",
68 |             "@stylistic/object-property-newline":                 "off",
69 |             "@stylistic/space-in-parens":                         "off",
70 |             "@stylistic/array-bracket-spacing":                   "off",
71 |             "@stylistic/lines-between-class-members":             "off",
72 |             "@stylistic/multiline-ternary":                       "off",
73 |             "@stylistic/quote-props":                             "off",
74 |             "@stylistic/indent":                                  "off",
75 | 
76 |             "@typescript-eslint/no-empty-function":               "off",
77 |             "@typescript-eslint/no-explicit-any":                 "off",
78 |             "@typescript-eslint/no-unused-vars":                  "off",
79 |             "@typescript-eslint/ban-ts-comment":                  "off",
80 |             "@typescript-eslint/no-this-alias":                   "off",
81 |             "@typescript-eslint/no-non-null-assertion":           "off",
82 |             "@typescript-eslint/consistent-type-definitions":     "off",
83 |             "@typescript-eslint/array-type":                      "off",
84 |             "@typescript-eslint/no-extraneous-class":             "off",
85 |             "@typescript-eslint/consistent-indexed-object-style": "off",
86 |             "@typescript-eslint/prefer-function-type":            "off",
87 |             "@typescript-eslint/no-unnecessary-type-constraint":  "off",
88 |             "@typescript-eslint/no-empty-object-type":            "off",
89 | 
90 |             "mocha/no-mocha-arrows":                              "off"
91 |         }
92 |     }
93 | ]
94 | 
95 | 


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29 |   <g>
30 |     <rect class="st2" x="413.5" y="402.7" width="161.4" height="161.4" rx="28.2" ry="28.2"/>
31 |     <path class="st1" d="M513.4,531.1v15.8c2.6,1.3,5.6,2.3,9.1,3s7.2,1,11.1,1,7.4-.4,10.8-1.1c3.4-.7,6.4-1.9,9-3.6,2.6-1.7,4.6-3.8,6.1-6.5s2.2-6,2.2-9.9-.4-5.4-1.3-7.5-2.1-4.1-3.7-5.7c-1.6-1.7-3.5-3.2-5.8-4.5s-4.8-2.6-7.6-3.8c-2.1-.9-3.9-1.7-5.6-2.5-1.6-.8-3-1.6-4.2-2.5-1.2-.8-2-1.7-2.7-2.7-.6-.9-.9-2-.9-3.2s.3-2.1.8-2.9,1.3-1.6,2.4-2.2c1-.6,2.3-1.1,3.7-1.5,1.5-.3,3.1-.5,4.9-.5s2.7,0,4.2.3c1.5.2,2.9.5,4.4.9,1.5.4,2.9.9,4.3,1.6,1.4.6,2.7,1.3,3.9,2.2v-14.7c-2.4-.9-5-1.6-7.9-2s-6.1-.7-9.8-.7-7.3.4-10.7,1.2-6.3,2.1-8.9,3.8c-2.5,1.7-4.6,3.9-6,6.5-1.5,2.6-2.2,5.8-2.2,9.5s1.4,8.7,4.1,12c2.7,3.3,6.8,6.1,12.4,8.4,2.2.9,4.2,1.8,6.1,2.6s3.5,1.7,4.9,2.7c1.4.9,2.4,1.9,3.2,3,.8,1.1,1.2,2.3,1.2,3.7s-.2,2-.7,2.8-1.2,1.6-2.2,2.3-2.3,1.1-3.7,1.5c-1.5.4-3.2.5-5.3.5-3.4,0-6.8-.6-10.2-1.8-3.4-1.2-6.5-3-9.3-5.4h0ZM486.9,492.3h20.2v-13h-56.4v13h20.1v57.7h16v-57.7Z"/>
32 |   </g>
33 |   <g>
34 |     <path class="st2" d="M82.8,104.4h-18.7v-13.2h53.5v13.2h-19v56.4h-15.8v-56.4Z"/>
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40 |   </g>
41 | </svg>


--------------------------------------------------------------------------------
/etc/nps.yaml:
--------------------------------------------------------------------------------
 1 | ##
 2 | ##  @rse/traits - Traits for TypeScript Classes
 3 | ##  Copyright (c) 2025 Dr. Ralf S. Engelschall <rse@engelschall.com>
 4 | ##  Licensed under MIT license <https://spdx.org/licenses/MIT>
 5 | ##
 6 | 
 7 | scripts:
 8 |     #   all-in-one development
 9 |     dev:                  nodemon --exec "npm start lint build test" --watch src --ext ts,1
10 | 
11 |     #   static code analysis (linting)
12 |     lint:                 eslint --config etc/eslint.mts src/**/*.ts
13 |     lint-watch:           nodemon --exec "npm start lint" --watch src --ext ts,1
14 | 
15 |     #   code compilation/transpiling (building)
16 |     build:                npm start lint build-esm build-umd
17 |     build-esm:            VITE_BUILD_FORMATS=esm,cjs vite --config etc/vite.mts build --mode production
18 |     build-umd:            VITE_BUILD_FORMATS=umd     vite --config etc/vite.mts build --mode production
19 |     build-watch:          nodemon --exec "npm start build" --watch src --ext ts,1
20 | 
21 |     #   test
22 |     test:                 NODE_OPTIONS="--import=tsx" mocha src/traits.spec.ts
23 | 
24 |     #   cleanup
25 |     clean:                shx rm -rf dst-stage1 dst-stage2
26 |     clean-dist:           npm start clean && shx rm -rf node_modules
27 | 
28 | 


--------------------------------------------------------------------------------
/etc/tsc.json:
--------------------------------------------------------------------------------
 1 | {
 2 |     "compilerOptions": {
 3 |         "outDir":                  "../dst",
 4 |         "target":                  "es2022",
 5 |         "module":                  "ESNext",
 6 |         "moduleResolution":        "Bundler",
 7 |         "useDefineForClassFields": false,
 8 |         "composite":               false,
 9 |         "strict":                  true,
10 |         "strictFunctionTypes":     true,
11 |         "resolveJsonModule":       false,
12 |         "isolatedModules":         false,
13 |         "esModuleInterop":         false,
14 |         "lib":                     [ "es2022" ],
15 |         "skipLibCheck":            false,
16 |         "declaration":             true,
17 |         "noEmit":                  false,
18 |         "types":                   [ "mocha" ],
19 |         "rootDir":                 "../src"
20 |     },
21 | 	"include": [
22 | 		"../src/**/*.ts",
23 | 		"../src/**/*.d.ts",
24 | 		"../package.json"
25 |     ],
26 |     "exclude": [
27 |         "../node_modules"
28 |     ]
29 | }
30 | 


--------------------------------------------------------------------------------
/etc/vite.mts:
--------------------------------------------------------------------------------
 1 | /*
 2 | **  @rse/traits - Traits for TypeScript Classes
 3 | **  Copyright (c) 2025 Dr. Ralf S. Engelschall <rse@engelschall.com>
 4 | **  Licensed under MIT license <https://spdx.org/licenses/MIT>
 5 | */
 6 | 
 7 | import fs                    from "node:fs"
 8 | import * as Vite             from "vite"
 9 | import { tscPlugin }         from "@wroud/vite-plugin-tsc"
10 | import { viteSingleFile }    from "vite-plugin-singlefile"
11 | import { nodePolyfills }     from "vite-plugin-node-polyfills"
12 | 
13 | const formats = process.env.VITE_BUILD_FORMATS ?? "esm"
14 | 
15 | export default Vite.defineConfig(({ command, mode }) => ({
16 |     logLevel: "info",
17 |     appType:  "custom",
18 |     base:     "",
19 |     root:     "",
20 |     plugins: [
21 |         tscPlugin({
22 |             tscArgs:        [ "--project", "etc/tsc.json" ],
23 |             packageManager: "npx",
24 |             prebuild:       true
25 |         }),
26 |         ...(formats === "umd" ? [ nodePolyfills() ] : []),
27 |         viteSingleFile()
28 |     ],
29 |     build: {
30 |         lib: {
31 |             entry:    "dst/traits.js",
32 |             formats:  formats.split(","),
33 |             name:     "Traits",
34 |             fileName: (format) => `traits.${format === "es" ? "esm" : format}.js`
35 |         },
36 |         target:                 "es2022",
37 |         outDir:                 "dst",
38 |         assetsDir:              "",
39 |         emptyOutDir:            (mode === "production") && formats !== "umd",
40 |         chunkSizeWarningLimit:  5000,
41 |         assetsInlineLimit:      0,
42 |         sourcemap:              (mode === "development"),
43 |         minify:                 (mode === "production") && formats === "umd",
44 |         reportCompressedSize:   (mode === "production")
45 |     }
46 | }))
47 | 
48 | 


--------------------------------------------------------------------------------
/package.json:
--------------------------------------------------------------------------------
 1 | {
 2 |     "name":                              "@traits-ts/core",
 3 |     "publishConfig":                     { "access": "public" },
 4 |     "description":                       "Traits for TypeScript Classes",
 5 |     "keywords":                          [ "traits", "class", "mixin" ],
 6 |     "homepage":                          "https://traits-ts.org",
 7 |     "repository":                        { "url": "git+https://github.com/traits-ts/core.git", "type": "git" },
 8 |     "bugs":                              { "url": "http://github.com/traits-ts/core/issues" },
 9 |     "version":                           "1.1.3",
10 |     "license":                           "MIT",
11 |     "author": {
12 |         "name":                          "Dr. Ralf S. Engelschall",
13 |         "email":                         "rse@engelschall.com",
14 |         "url":                           "http://engelschall.com"
15 |     },
16 |     "types":                             "./dst/traits.d.ts",
17 |     "module":                            "./dst/traits.esm.js",
18 |     "main":                              "./dst/traits.cjs.js",
19 |     "browser":                           "./dst/traits.umd.js",
20 |     "exports": {
21 |         ".": {
22 |             "import":                    { "types": "./dst/traits.d.ts", "default": "./dst/traits.esm.js" },
23 |             "require":                   { "types": "./dst/traits.d.ts", "default": "./dst/traits.cjs.js" }
24 |         }
25 |     },
26 |     "devDependencies": {
27 |         "eslint":                        "9.28.0",
28 |         "@eslint/js":                    "9.28.0",
29 |         "eslint-plugin-n":               "17.18.0",
30 |         "eslint-plugin-promise":         "7.2.1",
31 |         "eslint-plugin-import":          "2.31.0",
32 |         "eslint-plugin-mocha":           "11.1.0",
33 |         "eslint-plugin-chai-expect":     "3.1.0",
34 |         "neostandard":                   "0.12.1",
35 |         "globals":                       "16.2.0",
36 | 
37 |         "vite":                          "6.3.5",
38 |         "vite-plugin-singlefile":        "2.2.0",
39 |         "vite-plugin-node-polyfills":    "0.23.0",
40 |         "@wroud/vite-plugin-tsc":        "0.11.6",
41 |         "typescript":                    "5.8.3",
42 |         "tsx":                           "4.19.4",
43 |         "jiti":                          "2.4.2",
44 |         "mocha":                         "11.5.0",
45 |         "chai":                          "5.2.0",
46 |         "chai-as-promised":              "8.0.1",
47 |         "sinon-chai":                    "4.0.0",
48 |         "sinon":                         "20.0.0",
49 | 
50 |         "nps":                           "5.10.0",
51 |         "nodemon":                       "3.1.10",
52 |         "shx":                           "0.4.0",
53 | 
54 |         "@types/node":                   "22.15.29",
55 |         "@types/chai":                   "5.2.2",
56 |         "@types/mocha":                  "10.0.10",
57 |         "@types/sinon":                  "17.0.4",
58 |         "@types/sinon-chai":             "4.0.0",
59 |         "@types/chai-as-promised":       "8.0.2"
60 |     },
61 |     "scripts": {
62 |         "start":                         "nps -c etc/nps.yaml"
63 |     }
64 | }
65 | 


--------------------------------------------------------------------------------
/src/traits.spec.ts:
--------------------------------------------------------------------------------
  1 | /*
  2 | **  @traits-ts/core - Traits for TypeScript Classes
  3 | **  Copyright (c) 2025 Dr. Ralf S. Engelschall <rse@engelschall.com>
  4 | **  Licensed under MIT license <https://spdx.org/licenses/MIT>
  5 | */
  6 | 
  7 | import * as chai from "chai"
  8 | import sinon     from "sinon"
  9 | import sinonChai from "sinon-chai"
 10 | 
 11 | import { trait, derive, derived } from "./traits"
 12 | 
 13 | const expect = chai.expect
 14 | chai.config.includeStack = true
 15 | chai.use(sinonChai)
 16 | 
 17 | describe("@traits-ts/traits", () => {
 18 |     it("exposed API", () => {
 19 |         expect(trait).to.be.a("function")
 20 |         expect(derive).to.be.a("function")
 21 |         expect(derived).to.be.a("function")
 22 |     })
 23 | 
 24 |     it("basic derivation", () => {
 25 |         const Trait1 = trait((base) => class extends base {
 26 |             trait1 () {}
 27 |         })
 28 |         const Trait2 = <T>() => trait((base) => class extends base {
 29 |             trait2 () {}
 30 |         })
 31 |         class Clazz {
 32 |             clazz () {}
 33 |         }
 34 |         class Clazz2 {
 35 |             clazz2 () {}
 36 |         }
 37 |         const Sample = class Sample extends
 38 |             derive(Trait1, Clazz) {}
 39 |         const sample = new Sample()
 40 |         expect(sample.trait1).to.be.a("function")
 41 |         expect(sample.clazz).to.be.a("function")
 42 |         expect(derived(sample, Trait1)).to.be.equal(true)
 43 |         expect(derived(sample, Trait2)).to.be.equal(false)
 44 |         expect(derived(sample, Clazz)).to.be.equal(true)
 45 |         expect(derived(sample, Clazz2)).to.be.equal(false)
 46 |     })
 47 | 
 48 |     it("basic usage", () => {
 49 |         const Swim = trait((base) => class Swim extends base {
 50 |             static swimmers = 1
 51 |             swimming = 0
 52 |             swim () { return this.swimming++ }
 53 |         })
 54 |         const Walk = trait((base) => class Walk extends base {
 55 |             static walkers = 2
 56 |             static fastWalk () { return "fastWalk" }
 57 |             walking = 0
 58 |             walk () { return this.walking++ }
 59 |         })
 60 |         class Sample extends derive(Swim, Walk) {
 61 |             static samplers = 3
 62 |             sampling = 0
 63 |             perform () {
 64 |                 expect(this.sampling).to.be.equal(0)
 65 |                 expect(this.swimming).to.be.equal(0)
 66 |                 expect(this.walking).to.be.equal(0)
 67 |                 expect(this.swim()).to.be.equal(0)
 68 |                 expect(this.walk()).to.be.equal(0)
 69 |                 expect(this.swim()).to.be.equal(1)
 70 |                 expect(this.walk()).to.be.equal(1)
 71 |                 expect(this.swim()).to.be.equal(2)
 72 |                 expect(this.walk()).to.be.equal(2)
 73 |             }
 74 |         }
 75 |         const sample = new Sample()
 76 |         expect(Sample.swimmers).to.be.equal(1)
 77 |         expect(Sample.walkers).to.be.equal(2)
 78 |         expect(Sample.samplers).to.be.equal(3)
 79 |         expect(Sample.fastWalk()).to.be.equal("fastWalk")
 80 |         sample.perform()
 81 |     })
 82 | 
 83 |     it("complex usage", () => {
 84 |         const spy = sinon.spy()
 85 |         const Foo = trait((base) => class Foo extends base {
 86 |             constructor () { super(); spy("Foo") }
 87 |         })
 88 |         const Bar = <T extends any>() => trait((base) => class Bar extends base {
 89 |             constructor () { super(); spy("Bar") }
 90 |         })
 91 |         const Baz = trait([ Bar<string>, Foo ], (base) => class Baz extends base {
 92 |             constructor () { super(); spy("Baz") }
 93 |         })
 94 |         class App extends derive(Baz) {
 95 |             constructor () { super(); spy("App") }
 96 |         }
 97 |         const app = new App()
 98 |         expect(derived(app, Foo)).to.be.equal(true)
 99 |         expect(spy.getCalls().map((x) => x.args[0]))
100 |             .to.be.deep.equal([ "Foo", "Bar", "Baz", "App" ])
101 |     })
102 | 
103 |     it("double derivation", () => {
104 |         const spy = sinon.spy()
105 |         const Foo = trait((base) => class extends base {
106 |             constructor () { super(); spy("Foo") }
107 |         })
108 |         const Bar = trait([ Foo ], (base) => class extends base {
109 |             constructor () { super(); spy("Bar") }
110 |         })
111 |         const Baz = trait([ Bar, Foo ], (base) => class Baz extends base {
112 |             constructor () { super(); spy("Baz") }
113 |         })
114 |         class App extends derive(Baz, Foo, Foo) {
115 |             constructor () { super(); spy("App") }
116 |         }
117 |         const app = new App()
118 |         expect(spy.getCalls().map((x) => x.args[0]))
119 |             .to.be.deep.equal([ "Foo", "Bar", "Baz", "App" ])
120 |     })
121 | 
122 |     it("super usage", () => {
123 |         const Foo = trait((base) => class Foo extends base {
124 |             quux (arg: string) {
125 |                 return `foo.quux(${arg})`
126 |             }
127 |         })
128 |         const Bar = trait((base) => class Bar extends base {
129 |             quux (arg: string) {
130 |                 return `bar.quux(${super.quux(arg)})`
131 |             }
132 |         })
133 |         class App extends derive(Bar, Foo) {
134 |             quux (arg: string) {
135 |                 return `app.quux(${super.quux(arg)})`
136 |             }
137 |         }
138 |         const app = new App()
139 |         expect(app.quux("start")).to.be.equal("app.quux(bar.quux(foo.quux(start)))")
140 |     })
141 | 
142 |     it("constructor super usage", () => {
143 |         const spy = sinon.spy()
144 |         interface Sample {
145 |             foo1: string
146 |             foo2: number
147 |         }
148 |         const Foo = <T extends Sample>() => trait((base) => class Foo extends base {
149 |             constructor (params: { [ key: string ]: unknown; foo?: T } | undefined) {
150 |                 super(params)
151 |                 spy("Foo", params?.foo?.foo1 === "foo" && params?.foo?.foo2 === 7)
152 |             }
153 |         })
154 |         const Bar = trait([ Foo<Sample> ], (base) => class Bar extends base {
155 |             constructor (params: { [key: string ]: unknown; bar?: number } | undefined) {
156 |                 super(params)
157 |                 spy("Bar", params?.bar === 42)
158 |             }
159 |         })
160 |         class App extends derive(Bar) {
161 |             constructor () {
162 |                 super({ foo: { foo1: "foo", foo2: 7 }, bar: 42 })
163 |                 spy("App")
164 |             }
165 |         }
166 |         const app = new App()
167 |         expect(spy.getCalls().map((x) => x.args.join(":")))
168 |             .to.be.deep.equal([ "Foo:true", "Bar:true", "App" ])
169 |     })
170 | 
171 |     it("sample traits: regular, orthogonal", () => {
172 |         const Duck = trait((base) => class extends base {
173 |             squeak () { return "squeak" }
174 |         })
175 |         const Parrot = trait((base) => class extends base {
176 |             talk () { return "talk" }
177 |         })
178 |         const Animal = class Animal extends derive(Duck, Parrot) {
179 |             walk () { return "walk" }
180 |         }
181 |         const animal = new Animal()
182 |         expect(animal.squeak()).to.be.equal("squeak")
183 |         expect(animal.talk()).to.be.equal("talk")
184 |         expect(animal.walk()).to.be.equal("walk")
185 |     })
186 | 
187 |     it("sample traits: regular, bounded", () => {
188 |         const Queue = trait((base) => class extends base {
189 |             private buf: Array<number> = []
190 |             get () { return this.buf.pop() }
191 |             put (x: number) { this.buf.unshift(x) }
192 |         })
193 |         const Doubling = trait([ Queue ], (base) => class extends base {
194 |             put (x: number) { super.put(2 * x) }
195 |         })
196 |         const Incrementing = trait([ Queue ], (base) => class extends base {
197 |             put (x: number) { super.put(x + 1) }
198 |         })
199 |         const Filtering = trait([ Queue ], (base) => class extends base {
200 |             put (x: number) { if (x >= 0) super.put(x) }
201 |         })
202 | 
203 |         const MyQueue = class MyQueue extends
204 |             derive(Filtering, Doubling, Incrementing, Queue) {}
205 |         const queue = new MyQueue()
206 |         expect(queue.get()).to.be.equal(undefined)
207 |         queue.put(-1)
208 |         expect(queue.get()).to.be.equal(undefined)
209 |         queue.put(1)
210 |         expect(queue.get()).to.be.equal(3)
211 |         queue.put(10)
212 |         expect(queue.get()).to.be.equal(21)
213 |     })
214 | 
215 |     it("sample traits: generic, bounded", () => {
216 |         const Queue = <T>() => trait((base) => class extends base {
217 |             private buf: Array<T> = []
218 |             get () { return this.buf.pop() }
219 |             put (x: T) { this.buf.unshift(x) }
220 |         })
221 |         const Tracing = <T>() => trait([ Queue<T> ], (base) => class extends base {
222 |             public onTrace = (ev: string, x?: T) => {}
223 |             get () { const x = super.get(); this.onTrace("get", x); return x }
224 |             put (x: T) { this.onTrace("put", x); super.put(x) }
225 |         })
226 | 
227 |         const MyTracingQueue = class MyTracingQueue extends
228 |             derive(Tracing<string>, Queue<string>) {}
229 |         const spy = sinon.spy()
230 |         const queue = new MyTracingQueue()
231 |         queue.onTrace = (ev: string, x?: string) => { spy(ev, x) }
232 |         queue.put("foo")
233 |         queue.get()
234 |         queue.put("bar")
235 |         queue.put("qux")
236 |         queue.get()
237 |         queue.get()
238 |         expect(spy.getCalls().map((x) => x.args.join(":"))).to.be.deep.equal([
239 |             "put:foo", "get:foo", "put:bar", "put:qux", "get:bar", "get:qux"
240 |         ])
241 |     })
242 | })
243 | 


--------------------------------------------------------------------------------
/src/traits.ts:
--------------------------------------------------------------------------------
  1 | /*
  2 | **  @traits-ts/core - Traits for TypeScript Classes
  3 | **  Copyright (c) 2025 Dr. Ralf S. Engelschall <rse@engelschall.com>
  4 | **  Licensed under MIT license <https://spdx.org/licenses/MIT>
  5 | */
  6 | 
  7 | /* eslint no-use-before-define: off */
  8 | 
  9 | /*  ==== UTILITY DEFINITIONS ====  */
 10 | 
 11 | /*  utility function: CRC32-hashing a string into a unique identifier  */
 12 | const crcTable = [] as number[]
 13 | for (let n = 0; n < 256; n++) {
 14 |     let c = n
 15 |     for (let k = 0; k < 8; k++)
 16 |         c = ((c & 1) ? (0xEDB88320 ^ (c >>> 1)) : (c >>> 1))
 17 |     crcTable[n] = c
 18 | }
 19 | const crc32 = (str: string) => {
 20 |     let crc = 0 ^ (-1)
 21 |     for (let i = 0; i < str.length; i++)
 22 |         crc = (crc >>> 8) ^ crcTable[(crc ^ str.charCodeAt(i)) & 0xFF]
 23 |     return (crc ^ (-1)) >>> 0
 24 | }
 25 | 
 26 | /*  utility type and function: regular function  */
 27 | type Func<T extends any = any> =
 28 |     (...args: any[]) => T
 29 | const isFunc =
 30 |     <T extends any = any>
 31 |     (fn: unknown): fn is Func<T> =>
 32 |     typeof fn === "function" && !!fn.prototype && !!fn.prototype.constructor
 33 | 
 34 | /*  utility type and function: constructor (function)  */
 35 | type Cons<T extends any = any> =
 36 |     new (...args: any[]) => T
 37 | const isCons =
 38 |     <T extends any = any>
 39 |     (fn: unknown): fn is Cons<T> =>
 40 |     typeof fn === "function" && !!fn.prototype && !!fn.prototype.constructor
 41 | 
 42 | /*  utility type and function: constructor factory (function)  */
 43 | type ConsFactory<T extends Cons = Cons, B extends any = any> =
 44 |     (base: B) => T
 45 | const isConsFactory =
 46 |     <T extends Cons = Cons, B extends any = any>
 47 |     (fn: unknown): fn is ConsFactory<T, B> =>
 48 |     typeof fn === "function" && !fn.prototype && fn.length === 1
 49 | 
 50 | /*  utility type and function: type factory (function)  */
 51 | type TypeFactory<T extends any = any> =
 52 |     () => T
 53 | const isTypeFactory =
 54 |     <T extends any = any>
 55 |     (fn: unknown): fn is TypeFactory<T> =>
 56 |     typeof fn === "function" && !fn.prototype && fn.length === 0
 57 | 
 58 | /*  utility type: map an object type into a bare properties type  */
 59 | type Explode<T extends any> =
 60 |     { [ P in keyof T ]: T[P] }
 61 | 
 62 | /*  utility type: convert a union type to an intersection type  */
 63 | type UnionToIntersection<U> =
 64 |     (U extends any ? (k: U) => void : never) extends
 65 |     (k: infer I) => void ? I : never
 66 | 
 67 | /*  utility type: convert an array type to a union type  */
 68 | type ArrayToUnion<T extends any[]> =
 69 |     T[number]
 70 | 
 71 | /*  utility type: ensure that an array contains at least one element  */
 72 | type ArrayNonEmpty<T extends any[]> =
 73 |     [ T, ...T[] ]
 74 | 
 75 | /*  utility type: convert two arrays of types into an array of union types  */
 76 | type MixParams<T1 extends any[], T2 extends any[]> =
 77 |     T1 extends [] ? (
 78 |         T2 extends [] ? [] : T2
 79 |     ) : (
 80 |         T2 extends [] ? T1 : (
 81 |             T1 extends [ infer H1, ...infer R1 ] ? (
 82 |                 T2 extends [ infer H2, ...infer R2 ] ?
 83 |                     [ H1 & H2, ...MixParams<R1, R2> ]
 84 |                     : []
 85 |             ) : []
 86 |         )
 87 |     )
 88 | 
 89 | /*  ==== TRAIT DEFINITION ====  */
 90 | 
 91 | /*  API: trait type  */
 92 | type TraitDefTypeT  = ConsFactory<Cons>
 93 | type TraitDefTypeST = (Trait | TypeFactory<Trait>)[] | undefined
 94 | export type Trait<
 95 |     T  extends TraitDefTypeT  = TraitDefTypeT,
 96 |     ST extends TraitDefTypeST = TraitDefTypeST
 97 | > = {
 98 |     id:          number  /* unique id (primary,   for hasTrait)      */
 99 |     symbol:      symbol  /* unique id (secondary, currently unused)  */
100 |     factory:     T
101 |     superTraits: ST
102 | }
103 | 
104 | /*  API: generate trait (regular variant)  */
105 | /* eslint no-redeclare: off */
106 | export function trait<
107 |     T extends ConsFactory<Cons>
108 | > (factory: T): Trait<T, undefined>
109 | 
110 | /*  API: generate trait (super-trait variant)  */
111 | export function trait<
112 |     const ST extends (Trait | TypeFactory<Trait>)[],
113 |     T extends ConsFactory<Cons,
114 |         ST extends [ infer First, ...infer Rest ] ? (
115 |             First extends TypeFactory<Trait> ? ExtractFactory<ReturnType<First>> :
116 |             First extends Trait              ? ExtractFactory<First> :
117 |             any
118 |         ) : any
119 |     >
120 | > (superTraits: ST, factory: T): Trait<T, ST>
121 | 
122 | /*  API: generate trait (technical implementation)  */
123 | export function trait<
124 |     const ST extends (Trait | TypeFactory<Trait>)[],
125 |     T extends ConsFactory<Cons,
126 |         ST extends [ infer First, ...infer Rest ] ? (
127 |             First extends TypeFactory<Trait> ? ExtractFactory<ReturnType<First>> :
128 |             First extends Trait              ? ExtractFactory<First> :
129 |             any
130 |         ) : any
131 |     >
132 | > (...args: any[]): Trait<T, ST> {
133 |     const factory: T      = (args.length === 2 ? args[1] : args[0])
134 |     const superTraits: ST = (args.length === 2 ? args[0] : undefined)
135 |     return {
136 |         id: crc32(factory.toString()),
137 |         symbol: Symbol("trait"),
138 |         factory,
139 |         superTraits
140 |     }
141 | }
142 | 
143 | /*  ==== TRAIT DERIVATION ====  */
144 | 
145 | /*  ---- TRAIT PART EXTRACTION ----  */
146 | 
147 | /*  utility types: extract factory from a trait  */
148 | type ExtractFactory<
149 |     T extends Trait
150 | > =
151 |     T extends Trait<
152 |         ConsFactory<infer C>,
153 |         TraitDefTypeST
154 |     > ? C : never
155 | 
156 | /*  utility types: extract supertraits from a trait  */
157 | type ExtractSuperTrait<
158 |     T extends Trait
159 | > =
160 |     T extends Trait<
161 |         TraitDefTypeT,
162 |         infer ST extends TraitDefTypeST
163 |     > ? ST : never
164 | 
165 | /*  ---- TRAIT CONSTRUCTOR DERIVATION ----  */
166 | 
167 | /*  utility type: derive type constructor: merge two constructors  */
168 | type DeriveTraitsConsConsMerge<
169 |     A extends Cons,
170 |     B extends Cons
171 | > =
172 |     A extends (new (...args: infer ArgsA) => infer RetA) ? (
173 |         B extends (new (...args: infer ArgsB) => infer RetB) ? (
174 |             new (...args: MixParams<ArgsA, ArgsB>) => RetA & RetB
175 |         ) : never
176 |     ) : never
177 | 
178 | /*  utility type: derive type constructor: extract plain constructor  */
179 | type DeriveTraitsConsCons<
180 |     T extends Cons
181 | > =
182 |     new (...args: ConstructorParameters<T>) => InstanceType<T>
183 | 
184 | /*  utility type: derive type constructor: from trait parts  */
185 | type DeriveTraitsConsTraitParts<
186 |     C  extends Cons,
187 |     ST extends ((Trait | TypeFactory<Trait>)[] | undefined)
188 | > =
189 |     ST extends undefined ? DeriveTraitsConsCons<C> :
190 |     ST extends []        ? DeriveTraitsConsCons<C> :
191 |     DeriveTraitsConsConsMerge<
192 |         DeriveTraitsConsCons<C>,
193 |         DeriveTraitsConsAll<ST>> /* RECURSION */
194 | 
195 | /*  utility type: derive type constructor: from single trait  */
196 | type DeriveTraitsConsTrait<
197 |     T extends Trait
198 | > =
199 |     DeriveTraitsConsTraitParts<
200 |         ExtractFactory<T>,
201 |         ExtractSuperTrait<T>>
202 | 
203 | /*  utility type: derive type constructor: from single trait or trait factory  */
204 | type DeriveTraitsConsOne<
205 |     T extends (Trait | TypeFactory<Trait>)
206 | > =
207 |     T extends Trait              ? DeriveTraitsConsTrait<T>             :
208 |     T extends TypeFactory<Trait> ? DeriveTraitsConsTrait<ReturnType<T>> :
209 |     never
210 | 
211 | /*  utility type: derive type constructor: from one or more traits or trait factories  */
212 | type DeriveTraitsConsAll<
213 |     T extends (((Trait | TypeFactory<Trait>)[] | [ ...(Trait | TypeFactory<Trait>)[], Cons ]) | undefined)
214 | > =
215 |     T extends [ ...infer Others extends (Trait | TypeFactory<Trait>)[], infer Last extends Cons ] ? (
216 |         DeriveTraitsConsConsMerge<
217 |             DeriveTraitsConsAll<Others>, /* RECURSION */
218 |             DeriveTraitsConsCons<Last>>
219 |     ) :
220 |     T extends (Trait | TypeFactory<Trait>)[] ? (
221 |         T extends [ infer First extends (Trait | TypeFactory<Trait>) ] ? (
222 |             DeriveTraitsConsOne<First>
223 |         ) : (
224 |             T extends [
225 |                 infer    First extends (Trait | TypeFactory<Trait>),
226 |                 ...infer Rest  extends (Trait | TypeFactory<Trait>)[] ] ? (
227 |                 DeriveTraitsConsConsMerge<
228 |                     DeriveTraitsConsOne<First>,
229 |                     DeriveTraitsConsAll<Rest>> /* RECURSION */
230 |             ) : never
231 |         )
232 |     ) : never
233 | 
234 | /*  utility type: derive type constructor  */
235 | type DeriveTraitsCons<
236 |     T extends ((Trait | TypeFactory<Trait>)[] | [ ...(Trait | TypeFactory<Trait>)[], Cons ])
237 | > =
238 |     DeriveTraitsConsAll<T>
239 | 
240 | /*  ---- TRAIT STATICS DERIVATION ----  */
241 | 
242 | /*  utility type: derive type statics: merge two objects with statics  */
243 | type DeriveTraitsStatsConsMerge<
244 |     T1 extends {},
245 |     T2 extends {}
246 | > =
247 |     T1 & T2
248 | 
249 | /*  utility type: derive type statics: extract plain statics  */
250 | type DeriveTraitsStatsCons<
251 |     T extends Cons
252 | > =
253 |     Explode<T>
254 | 
255 | /*  utility type: derive type statics: from trait parts  */
256 | type DeriveTraitsStatsTraitParts<
257 |     C  extends Cons,
258 |     ST extends ((Trait | TypeFactory<Trait>)[] | undefined)
259 | > =
260 |     ST extends undefined ? DeriveTraitsStatsCons<C> :
261 |     ST extends []        ? DeriveTraitsStatsCons<C> :
262 |     DeriveTraitsStatsConsMerge<
263 |         DeriveTraitsStatsCons<C>,
264 |         DeriveTraitsStatsAll<ST>> /* RECURSION */
265 | 
266 | /*  utility type: derive type statics: from single trait  */
267 | type DeriveTraitsStatsTrait<
268 |     T extends Trait
269 | > =
270 |     DeriveTraitsStatsTraitParts<
271 |         ExtractFactory<T>,
272 |         ExtractSuperTrait<T>>
273 | 
274 | /*  utility type: derive type statics: from single trait or trait factory  */
275 | type DeriveTraitsStatsOne<
276 |     T extends (Trait | TypeFactory<Trait>)
277 | > =
278 |     T extends Trait              ? DeriveTraitsStatsTrait<T>             :
279 |     T extends TypeFactory<Trait> ? DeriveTraitsStatsTrait<ReturnType<T>> :
280 |     never
281 | 
282 | /*  utility type: derive type statics: from one or more traits or trait factories  */
283 | type DeriveTraitsStatsAll<
284 |     T extends (((Trait | TypeFactory<Trait>)[] | [ ...(Trait | TypeFactory<Trait>)[], Cons ]) | undefined)
285 | > =
286 |     T extends [ ...infer Others extends (Trait | TypeFactory<Trait>)[], infer Last extends Cons ] ? (
287 |         DeriveTraitsStatsConsMerge<
288 |             DeriveTraitsStatsAll<Others>, /* RECURSION */
289 |             DeriveTraitsStatsCons<Last>>
290 |     ) :
291 |     T extends (Trait | TypeFactory<Trait>)[] ? (
292 |         T extends [ infer First extends (Trait | TypeFactory<Trait>) ] ? (
293 |             DeriveTraitsStatsOne<First>
294 |         ) : (
295 |             T extends [
296 |                 infer    First extends (Trait | TypeFactory<Trait>),
297 |                 ...infer Rest  extends (Trait | TypeFactory<Trait>)[] ] ? (
298 |                 DeriveTraitsStatsConsMerge<
299 |                     DeriveTraitsStatsOne<First>,
300 |                     DeriveTraitsStatsAll<Rest>> /* RECURSION */
301 |             ) : never
302 |         )
303 |     ) : never
304 | 
305 | /*  utility type: derive type statics  */
306 | type DeriveTraitsStats<
307 |     T extends ((Trait | TypeFactory<Trait>)[] | [ ...(Trait | TypeFactory<Trait>)[], Cons ])
308 | > =
309 |     DeriveTraitsStatsAll<T>
310 | 
311 | /*  ---- TRAIT DERIVATION ----  */
312 | 
313 | /*  utility type: derive type from one or more traits or trait type factories  */
314 | type DeriveTraits<
315 |     T extends ((Trait | TypeFactory<Trait>)[] | [ ...(Trait | TypeFactory<Trait>)[], Cons ])
316 | > =
317 |     DeriveTraitsCons<T> &
318 |     DeriveTraitsStats<T>
319 | 
320 | /*  ---- TRAIT DERIVATION RUNTIME ----  */
321 | 
322 | /*  utility function: add an additional invisible property to an object  */
323 | const extendProperties =
324 |     (cons: Cons, field: string | symbol, value: any) =>
325 |     Object.defineProperty(cons, field, { value, enumerable: false, writable: false })
326 | 
327 | /*  utility function: get raw trait  */
328 | const rawTrait = (x: (Trait | TypeFactory<Trait>)) =>
329 |     isTypeFactory(x) ? x() : x
330 | 
331 | /*  utility function: derive a trait  */
332 | const deriveTrait = (
333 |     trait$:  Trait | TypeFactory<Trait>,
334 |     baseClz: Cons<any>,
335 |     derived: Map<number, boolean>
336 | ) => {
337 |     /*  get real trait  */
338 |     const trait = rawTrait(trait$)
339 | 
340 |     /*  start with base class  */
341 |     let clz = baseClz
342 | 
343 |     /*  in case we still have not derived this trait...  */
344 |     if (!derived.has(trait.id)) {
345 |         derived.set(trait.id, true)
346 | 
347 |         /*  iterate over all of its super traits  */
348 |         if (trait.superTraits !== undefined)
349 |             for (const superTrait of reverseTraitList(trait.superTraits))
350 |                 clz = deriveTrait(superTrait, clz, derived) /*  RECURSION  */
351 | 
352 |         /*  derive this trait  */
353 |         clz = trait.factory(clz)
354 |         extendProperties(clz, "id", crc32(trait.factory.toString()))
355 |         extendProperties(clz, trait.symbol, true)
356 |     }
357 | 
358 |     return clz
359 | }
360 | 
361 | /*  utility function: get reversed trait list  */
362 | const reverseTraitList = (traits: (Trait | TypeFactory<Trait>)[]) =>
363 |     traits.slice().reverse() as (Trait | TypeFactory<Trait>)[]
364 | 
365 | /*  API: type derive  */
366 | export function derive
367 |     <T extends (
368 |         [ Trait | TypeFactory<Trait>, ...(Trait | TypeFactory<Trait>)[] ] |
369 |         [ ...(Trait | TypeFactory<Trait>)[], Cons ]
370 |     )>
371 |     (...traits: T): DeriveTraits<T> {
372 |     /*  run-time sanity check  */
373 |     if (traits.length === 0)
374 |         throw new Error("invalid number of parameters (expected one or more traits)")
375 | 
376 |     /*  determine the base class (clz) and the list of traits (lot)  */
377 |     let clz: Cons<any>
378 |     let lot: (Trait | TypeFactory<Trait>)[]
379 |     const last = traits[traits.length - 1]
380 |     if (isCons(last) && !isTypeFactory(last)) {
381 |         /*  case 1: with trailing regular class  */
382 |         clz = last
383 |         lot = traits.slice(0, traits.length - 1) as (Trait | TypeFactory<Trait>)[]
384 |     }
385 |     else {
386 |         /*  case 2: just regular traits or trait type factories  */
387 |         clz = class ROOT {}
388 |         lot = traits as (Trait | TypeFactory<Trait>)[]
389 |     }
390 | 
391 |     /*  track already derived traits  */
392 |     const derived = new Map<number, boolean>()
393 | 
394 |     /*  iterate over all traits  */
395 |     for (const trait of reverseTraitList(lot))
396 |         clz = deriveTrait(trait, clz, derived)
397 | 
398 |     return clz as DeriveTraits<T>
399 | }
400 | 
401 | /*  ==== TRAIT TYPE-GUARDING ====  */
402 | 
403 | /*  internal type: implements trait type  */
404 | type DerivedType<T extends Trait> =
405 |     InstanceType<ExtractFactory<T>>
406 | 
407 | /*  internal type: implements trait type or trait type factory  */
408 | type Derived<T extends (Trait | TypeFactory<Trait> | Cons)> =
409 |     T extends TypeFactory<Trait> ? DerivedType<ReturnType<T>> :
410 |     T extends Trait              ? DerivedType<T> :
411 |     T extends Cons               ? T :
412 |     never
413 | 
414 | /*  API: type guard for checking whether class instance is derived from a trait  */
415 | export function derived
416 |     <T extends (Trait | TypeFactory<Trait> | Cons)>
417 |     (instance: unknown, trait: T): instance is Derived<T> {
418 |     /*  ensure the class instance is really an object  */
419 |     if (typeof instance !== "object")
420 |         return false
421 |     let obj = instance
422 | 
423 |     if (isCons(trait) && !isTypeFactory(trait)) {
424 |         /*  special case: regular class  */
425 |         return (instance instanceof trait)
426 |     }
427 |     else {
428 |         /*  regular case: trait or trait type factory  */
429 | 
430 |         /*  determine unique id of trait  */
431 |         const t = (isTypeFactory(trait) ? trait() : trait) as Trait
432 |         const idTrait = t["id"]
433 | 
434 |         /*  iterate over class/trait hierarchy  */
435 |         while (obj) {
436 |             if (Object.hasOwn(obj, "constructor")) {
437 |                 const id = ((obj.constructor as any)["id"] as number) ?? 0
438 |                 if (id === idTrait)
439 |                     return true
440 |             }
441 |             obj = Object.getPrototypeOf(obj)
442 |         }
443 |     }
444 |     return false
445 | }
446 | 
447 | 


--------------------------------------------------------------------------------
/tsconfig.json:
--------------------------------------------------------------------------------
1 | {
2 |     "extends": "./etc/tsc.json"
3 | }
4 | 


--------------------------------------------------------------------------------