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No files matched your search
+5
-1
@@ -7,8 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
|
||||
|
||||
## [Unreleased]
|
||||
|
||||
## [0.2.0] - 2026-09-16
|
||||
|
||||
- allow ternaries and lowercase comments in oxlint
|
||||
- switch `src/primitive.ts` prose from block comments to line comments
|
||||
- remove the template's `match`/`P` example modules and their documentation, and point `src/index.ts` at the primitive matchers
|
||||
|
||||
## [0.1.8] - 2026-09-16
|
||||
|
||||
@@ -51,7 +54,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
|
||||
|
||||
- basic setup
|
||||
|
||||
[Unreleased]: https://gitea.e1nsnull.de/tmu/tiny-pattern-ts/compare/0.1.8...main
|
||||
[Unreleased]: https://gitea.e1nsnull.de/tmu/tiny-pattern-ts/compare/0.2.0...main
|
||||
[0.2.0]: https://gitea.e1nsnull.de/tmu/tiny-pattern-ts/compare/0.1.8...0.2.0
|
||||
[0.1.8]: https://gitea.e1nsnull.de/tmu/tiny-pattern-ts/compare/0.1.7...0.1.8
|
||||
[0.1.7]: https://gitea.e1nsnull.de/tmu/tiny-pattern-ts/compare/0.1.6...0.1.7
|
||||
[0.1.6]: https://gitea.e1nsnull.de/tmu/tiny-pattern-ts/compare/0.1.5...0.1.6
|
||||
|
||||
@@ -2,34 +2,14 @@
|
||||
|
||||
Pattern matching for TypeScript/ESM environments (F#-style, not regex).
|
||||
|
||||
## Synopsis
|
||||
|
||||
```ts
|
||||
import { match, P } from "tiny-pattern-ts";
|
||||
|
||||
const reply = (answer: "yes" | "no") =>
|
||||
match(answer)
|
||||
.with(P.literal("yes"), (): "agreed" => "agreed")
|
||||
.with(P.literal("no"), (): "declined" => "declined")
|
||||
.exhaustive();
|
||||
|
||||
reply("yes"); // "agreed"
|
||||
```
|
||||
|
||||
## Description
|
||||
|
||||
`tiny-pattern-ts` gives TypeScript the shape of F#-style pattern matching:
|
||||
a value flows through a chain of patterns, the first one that matches runs its
|
||||
handler, and the handler receives the value narrowed to that pattern's type. The
|
||||
"patterns" are ordinary objects whose `matches` method is a TypeScript type
|
||||
guard, so narrowing composes the way any other guard does.
|
||||
|
||||
It is deliberately not a regex engine and not a macro. There is no transpiler
|
||||
and no DSL to learn: `match(value)` returns a builder, `.with(pattern, handler)`
|
||||
adds a case, and the chain ends in either `.exhaustive()` or `.otherwise(...)`.
|
||||
The type-level contract is the feature — see
|
||||
[development/library.md](./development/library.md) for the design decisions and
|
||||
the known limitations.
|
||||
`tiny-pattern-ts` brings F#-style pattern matching to TypeScript. Patterns are
|
||||
ordinary objects whose `matches` method is a TypeScript type guard, so narrowing
|
||||
composes the way any other guard does. It is deliberately not a regex engine and
|
||||
not a macro: there is no transpiler and no DSL to learn, and the type-level
|
||||
contract is the feature — see [development/library.md](./development/library.md)
|
||||
for the design decisions and the known limitations.
|
||||
|
||||
## Requirements
|
||||
|
||||
@@ -39,124 +19,6 @@ the known limitations.
|
||||
both resolve on TS >= 5.0 in `node10` / `node16` / `nodenext` / `bundler`.
|
||||
- The package is **ESM-only** (no CommonJS shim).
|
||||
|
||||
## Examples
|
||||
|
||||
### Literal matching and `exhaustive()`
|
||||
|
||||
`.exhaustive()` returns the union of the handler return types and throws if no
|
||||
case matched. Annotate handler returns when you want literal types rather than
|
||||
`string`:
|
||||
|
||||
```ts
|
||||
type Answer = "yes" | "no";
|
||||
|
||||
const reply = (answer: Answer): "agreed" | "declined" =>
|
||||
match(answer)
|
||||
.with(P.literal("yes"), (): "agreed" => "agreed")
|
||||
.with(P.literal("no"), (): "declined" => "declined")
|
||||
.exhaustive();
|
||||
|
||||
reply("yes"); // "agreed"
|
||||
```
|
||||
|
||||
`exhaustive()` checks at runtime, not at compile time — TypeScript does not force
|
||||
every union member to have a case (see
|
||||
[development/library.md](./development/library.md#exhaustive-is-a-runtime-check)).
|
||||
Use `.otherwise(...)` when a fallback is wanted:
|
||||
|
||||
```ts
|
||||
const label = (answer: Answer): string =>
|
||||
match(answer)
|
||||
.with(P.literal("yes"), () => "agreed")
|
||||
.otherwise(() => "not agreed");
|
||||
```
|
||||
|
||||
### Matching by `typeof`
|
||||
|
||||
`P.type<T>(name)` pairs an explicit type `T` with the runtime `typeof` name it
|
||||
should test for:
|
||||
|
||||
```ts
|
||||
const describe = (value: unknown): string =>
|
||||
match(value)
|
||||
.with(P.type<string>("string"), (s) => `string of length ${s.length}`)
|
||||
.with(P.type<number>("number"), (n) => `number ${n.toFixed(2)}`)
|
||||
.otherwise(() => "something else");
|
||||
```
|
||||
|
||||
The supported names are `string`, `number`, `boolean`, `bigint`, `symbol`,
|
||||
`undefined`, `object`, and `function`. `"object"` matches non-null objects and
|
||||
functions; `"undefined"` compares against `undefined` directly.
|
||||
|
||||
### Structural matching and discriminated unions
|
||||
|
||||
`P.shape(shape, refine?)` checks that every key in `shape` exists on the value.
|
||||
A value that is itself a matcher is applied, otherwise it is compared with
|
||||
strict equality. To narrow to a concrete type, pass a `refine` type guard:
|
||||
|
||||
```ts
|
||||
interface Circle {
|
||||
readonly kind: "circle";
|
||||
readonly radius: number;
|
||||
}
|
||||
|
||||
interface Square {
|
||||
readonly kind: "square";
|
||||
readonly side: number;
|
||||
}
|
||||
|
||||
type Shape = Circle | Square;
|
||||
|
||||
const area = (shape: Shape): number =>
|
||||
match(shape)
|
||||
.with(
|
||||
P.shape({ kind: "circle" }, (v): v is Circle => "radius" in v),
|
||||
(c) => Math.PI * c.radius ** 2,
|
||||
)
|
||||
.with(
|
||||
P.shape({ kind: "square" }, (v): v is Square => "side" in v),
|
||||
(s) => s.side ** 2,
|
||||
)
|
||||
.exhaustive();
|
||||
```
|
||||
|
||||
Without `refine`, `P.shape` returns a matcher for the shape's own type, not the
|
||||
narrowed one. Nested matchers can be used in the shape object, for example
|
||||
`P.shape({ name: P.type<string>("string") })`.
|
||||
|
||||
### Custom guards with `when`
|
||||
|
||||
`P.when` takes a type guard and infers the narrowed type from it:
|
||||
|
||||
```ts
|
||||
const toNumber = (value: unknown): number =>
|
||||
match(value)
|
||||
.with(
|
||||
P.when((v): v is string => typeof v === "string"),
|
||||
(s) => Number.parseInt(s, 10),
|
||||
)
|
||||
.otherwise(() => 0);
|
||||
```
|
||||
|
||||
### Widening with `any`
|
||||
|
||||
`P.any<T>(predicate)` takes a plain boolean predicate and a declared type `T`,
|
||||
for cases where the predicate cannot be written as a type guard:
|
||||
|
||||
```ts
|
||||
const firstNumber = (items: readonly unknown[]): number | undefined =>
|
||||
match(items)
|
||||
.with(
|
||||
P.any<readonly number[]>(
|
||||
(v) =>
|
||||
Array.isArray(v) &&
|
||||
v.every((item) => typeof item === "number"),
|
||||
),
|
||||
(xs) => xs[0],
|
||||
)
|
||||
.otherwise(() => undefined);
|
||||
```
|
||||
|
||||
## API
|
||||
|
||||
Yet to be implemented
|
||||
|
||||
+12
-3
@@ -5,20 +5,26 @@ Backlog and tracking for tiny-pattern-ts. Managed in vscode-todotasks format.
|
||||
---
|
||||
|
||||
Setup:
|
||||
☐ Split off template into separate package => pi --session 01a07dde-7050-7054-bb36-1606d7eb2bc3 @high
|
||||
☐ Split off template into separate package => pi --session 01a07dde-7050-7054-bb36-1606d7eb2bc3 @low
|
||||
✔ straighten oxc rules @done
|
||||
✔ oxc forbids ternary => remove oxc rule @done
|
||||
✔ oxc wants comments to start comments with a capital letter => remove oxc rule @done
|
||||
✔ there already exists a /* */ block comment in primitive.ts, => change to multi-line comment @done
|
||||
|
||||
✔ Remove example code files and its documentation and its exports from index.ts @high @done
|
||||
✔ remove src/match.ts and its documentation @high @done
|
||||
✔ remove src/pattern.ts and its documentation @high @done
|
||||
✔ remove src/index.test.ts and its documentation @high @done
|
||||
✔ exports from `src/index.ts` should only be the public API surface @done
|
||||
|
||||
|
||||
v1.0:
|
||||
☐ API surface is stable and fully typed
|
||||
☐ Finalize public exports in `src/index.ts`
|
||||
☐ Document all exported types and functions
|
||||
☐ Add JSDoc for public APIs
|
||||
☐ Test coverage meets threshold
|
||||
☐ Achieve 100% branch coverage on `src/pattern.ts`
|
||||
☐ Achieve 100% branch coverage on `src/match.ts`
|
||||
☐ Achieve 100% branch coverage on `src/primitive.ts`
|
||||
☐ Achieve 100% branch coverage on `src/index.ts`
|
||||
|
||||
Bugs:
|
||||
@@ -28,6 +34,9 @@ Enhancements:
|
||||
☐ Are there other primitive types that should be supported in union patterns? (e.g. `bigint`, `symbol`) @medium
|
||||
|
||||
Documentation:
|
||||
☐ Bring README.md back to its previous form — synopsis and examples restored, in the correct place
|
||||
→ previous section order: title, tagline, Synopsis, Description, Requirements, Examples, API, License, Contributing
|
||||
→ previous Examples order: literal/exhaustive, typeof, structural/discriminated unions, when, any
|
||||
☐ Create `examples/` directory with runnable snippets
|
||||
☐ Add comparison section vs. other TS pattern-matching libs in Readme.md
|
||||
☐ Write migration guide for users coming from discriminated unions
|
||||
|
||||
@@ -27,8 +27,8 @@ before the implementation.
|
||||
|
||||
- Runtime-first (classic red/green): it verifies the value, not the contract,
|
||||
and the contract is the product.
|
||||
- Testing the type only: it would not catch handler wiring, `exhaustive()`
|
||||
throwing, or the `otherwise` fallback (see `src/index.test.ts`).
|
||||
- Testing the type only: it would not catch handler dispatch or the `_`
|
||||
fallback (see `src/primitive.test.ts`).
|
||||
|
||||
The runner is `node --test --strip-types "src/**/*.test.ts"` and the tiers are in
|
||||
[CONTRIBUTING.md § Development commands](../CONTRIBUTING.md#development-commands).
|
||||
@@ -66,7 +66,7 @@ separated by a blank line; an empty block drops its label.
|
||||
## Known issues
|
||||
|
||||
- The type-aware linter misidentifies `expectTypeOf()` as a floating promise, so
|
||||
test files that use it (`src/index.test.ts`, `src/primitive.test.ts`) carry a
|
||||
test files that use it (`src/primitive.test.ts`) carry a
|
||||
file-level `oxlint-disable
|
||||
typescript/no-floating-promises` with an explanatory comment. It is a known
|
||||
false positive, not a rule worth disabling project-wide (see
|
||||
|
||||
@@ -105,8 +105,8 @@ Type-aware oxlint is enabled via `options.typeAware: true` in `.oxlintrc.json`
|
||||
#### Decision (2026-09)
|
||||
|
||||
A type-aware rule that false-positives is silenced with a source-level
|
||||
`oxlint-disable` directive (see `src/pattern.ts`, `src/match.ts`,
|
||||
`src/index.test.ts`), not by turning the rule off in `.oxlintrc.json`.
|
||||
`oxlint-disable` directive (see `src/primitive.ts`,
|
||||
`src/primitive.test.ts`), not by turning the rule off in `.oxlintrc.json`.
|
||||
|
||||
#### Why
|
||||
|
||||
|
||||
Generated
+2
-2
@@ -1,12 +1,12 @@
|
||||
{
|
||||
"name": "tiny-pattern-ts",
|
||||
"version": "0.1.8",
|
||||
"version": "0.2.0",
|
||||
"lockfileVersion": 3,
|
||||
"requires": true,
|
||||
"packages": {
|
||||
"": {
|
||||
"name": "tiny-pattern-ts",
|
||||
"version": "0.1.8",
|
||||
"version": "0.2.0",
|
||||
"license": "MIT",
|
||||
"dependencies": {
|
||||
"type-fest": "^5.9.0"
|
||||
|
||||
+1
-1
@@ -1,6 +1,6 @@
|
||||
{
|
||||
"name": "tiny-pattern-ts",
|
||||
"version": "0.1.8",
|
||||
"version": "0.2.0",
|
||||
"description": "Pattern matching for TypeScript/ESM environments (F#-style, not regex)",
|
||||
"keywords": [
|
||||
"adt",
|
||||
|
||||
@@ -1,71 +0,0 @@
|
||||
/* oxlint-disable typescript/no-floating-promises -- expectTypeOf() is a sync type-assertion library that the type-aware linter misidentifies as a promise */
|
||||
import { strict as assert } from "node:assert";
|
||||
import { test } from "node:test";
|
||||
|
||||
import { expectTypeOf } from "expect-type";
|
||||
|
||||
import { type Matcher, P, match } from "./index.ts";
|
||||
|
||||
test("match returns a builder", () => {
|
||||
// Act
|
||||
const builder = match("x");
|
||||
|
||||
// Assert
|
||||
expectTypeOf(builder).toHaveProperty("with");
|
||||
expectTypeOf(builder).toHaveProperty("exhaustive");
|
||||
expectTypeOf(builder).toHaveProperty("otherwise");
|
||||
});
|
||||
|
||||
test("P.literal narrows to its literal type", () => {
|
||||
// Act
|
||||
const matcher = P.literal("yes");
|
||||
|
||||
// Assert
|
||||
expectTypeOf(matcher).toExtend<Matcher<"yes">>();
|
||||
assert.equal(matcher.matches("yes"), true);
|
||||
assert.equal(matcher.matches("no"), false);
|
||||
});
|
||||
|
||||
test("P.type narrows to the typeof target", () => {
|
||||
// Act
|
||||
const matcher = P.type<string>("string");
|
||||
|
||||
// Assert
|
||||
expectTypeOf(matcher).toExtend<Matcher<string>>();
|
||||
assert.equal(matcher.matches("hi"), true);
|
||||
assert.equal(matcher.matches(42), false);
|
||||
});
|
||||
|
||||
test("exhaustive() returns the union of handler return types", () => {
|
||||
// Act
|
||||
const result = match<"a" | "b">("a")
|
||||
.with(P.literal("a"), () => 1 as const)
|
||||
.with(P.literal("b"), () => "two" as const)
|
||||
.exhaustive();
|
||||
|
||||
// Assert
|
||||
expectTypeOf(result).toEqualTypeOf<1 | "two">();
|
||||
assert.equal(result, 1);
|
||||
});
|
||||
|
||||
test("otherwise() falls back when no case matches", () => {
|
||||
// Act
|
||||
const result = match<"x" | "y" | "z">("z")
|
||||
.with(P.literal("x"), (v): string => `got ${v}`)
|
||||
.otherwise((v): string => `fallback ${v}`);
|
||||
|
||||
// Assert
|
||||
assert.equal(result, "fallback z");
|
||||
});
|
||||
|
||||
test("exhaustive throws when no case matches", () => {
|
||||
// Assert
|
||||
assert.throws(
|
||||
() =>
|
||||
match<"a" | "b" | "c">("c")
|
||||
.with(P.literal("a"), () => "A")
|
||||
.with(P.literal("b"), () => "B")
|
||||
.exhaustive(),
|
||||
/no matching case/,
|
||||
);
|
||||
});
|
||||
+6
-2
@@ -1,2 +1,6 @@
|
||||
export { match, P } from "./match.ts";
|
||||
export type { Matcher, Pattern } from "./pattern.ts";
|
||||
export {
|
||||
getPrimitiveUnionMatcher,
|
||||
getPrimitiveUnionMatcherPartial,
|
||||
getPrimitiveUnionMatcherPartialW,
|
||||
getPrimitiveUnionMatcherW,
|
||||
} from "./primitive.ts";
|
||||
@@ -1,62 +0,0 @@
|
||||
import { P, type Matcher, type Pattern } from "./pattern.ts";
|
||||
|
||||
type Cases<R> = readonly (readonly [Matcher<unknown>, (value: unknown) => R])[];
|
||||
|
||||
interface MatchBuilder<T, R> {
|
||||
with<U extends T, V>(
|
||||
pattern: Matcher<U>,
|
||||
handler: (value: U) => V,
|
||||
): MatchBuilder<T, R | V>;
|
||||
exhaustive(): R;
|
||||
otherwise(handler: (value: T) => R): R;
|
||||
}
|
||||
|
||||
const buildMatch = <T, R>(value: T, cases: Cases<R>): MatchBuilder<T, R> => {
|
||||
const apply = (): R | undefined => {
|
||||
for (const [matcher, handler] of cases) {
|
||||
if (matcher.matches(value)) {
|
||||
return handler(value);
|
||||
}
|
||||
}
|
||||
return undefined;
|
||||
};
|
||||
|
||||
const builder = {
|
||||
with<U extends T, V>(
|
||||
pattern: Matcher<U>,
|
||||
handler: (value: U) => V,
|
||||
): MatchBuilder<T, R | V> {
|
||||
const nextCases: Cases<R | V> = [
|
||||
...cases,
|
||||
// oxlint-disable-next-line typescript/no-unsafe-type-assertion
|
||||
[pattern, handler as (value: unknown) => R | V],
|
||||
];
|
||||
return buildMatch(value, nextCases);
|
||||
},
|
||||
exhaustive(): R {
|
||||
const result = apply();
|
||||
if (result === undefined) {
|
||||
throw new Error(
|
||||
"tiny-pattern-ts: match.exhaustive() called with no matching case",
|
||||
);
|
||||
}
|
||||
return result;
|
||||
},
|
||||
otherwise(handler: (value: T) => R): R {
|
||||
for (const [matcher, run] of cases) {
|
||||
if (matcher.matches(value)) {
|
||||
return run(value);
|
||||
}
|
||||
}
|
||||
return handler(value);
|
||||
},
|
||||
};
|
||||
|
||||
return builder;
|
||||
};
|
||||
|
||||
export const match = <T>(value: T): MatchBuilder<T, never> =>
|
||||
buildMatch<T, never>(value, []);
|
||||
|
||||
export type { Matcher, Pattern };
|
||||
export { P };
|
||||
-105
@@ -1,105 +0,0 @@
|
||||
/**
|
||||
* Pattern matching primitives. Each constructor returns a lightweight
|
||||
* matcher object whose `matches` method returns a type guard.
|
||||
*/
|
||||
|
||||
export interface Matcher<T> {
|
||||
readonly matches: (value: unknown) => value is T;
|
||||
}
|
||||
|
||||
const literalMatcher = <
|
||||
const L extends string | number | boolean | null | undefined,
|
||||
>(
|
||||
value: L,
|
||||
): Matcher<L> => ({
|
||||
matches: (candidate): candidate is L => candidate === value,
|
||||
});
|
||||
const typeMatcher = <T>(
|
||||
type:
|
||||
| "string"
|
||||
| "number"
|
||||
| "boolean"
|
||||
| "bigint"
|
||||
| "symbol"
|
||||
| "undefined"
|
||||
| "object"
|
||||
| "function",
|
||||
): Matcher<T> => {
|
||||
const matches = (value: unknown): value is T => {
|
||||
if (type === "undefined") {
|
||||
return value === undefined;
|
||||
}
|
||||
if (type === "object") {
|
||||
return (
|
||||
(typeof value === "object" && value !== null) ||
|
||||
typeof value === "function"
|
||||
);
|
||||
}
|
||||
return typeof value === type;
|
||||
};
|
||||
return { matches };
|
||||
},
|
||||
whenMatcher = <T>(
|
||||
predicate: (value: unknown) => value is T,
|
||||
): Matcher<T> => ({
|
||||
matches: predicate,
|
||||
}),
|
||||
whenMatcherAny = <T>(
|
||||
predicate: (value: unknown) => boolean,
|
||||
): Matcher<T> => ({
|
||||
matches: (value: unknown): value is T => predicate(value),
|
||||
}),
|
||||
isNestedMatcher = (expected: unknown): expected is Matcher<unknown> =>
|
||||
typeof expected === "object" &&
|
||||
expected !== null &&
|
||||
"matches" in expected,
|
||||
// oxlint-disable-next-line typescript/no-unnecessary-type-parameters
|
||||
keysMatch = <S extends object>(shape: S, candidate: object): boolean => {
|
||||
// oxlint-disable-next-line typescript/no-unsafe-type-assertion
|
||||
for (const key of Object.keys(shape) as (keyof S)[]) {
|
||||
if (!(key in candidate)) {
|
||||
return false;
|
||||
}
|
||||
// oxlint-disable-next-line typescript/no-unsafe-type-assertion
|
||||
const expected = shape[key],
|
||||
// oxlint-disable-next-line typescript/no-unsafe-type-assertion
|
||||
actual = candidate[key as keyof object];
|
||||
if (isNestedMatcher(expected)) {
|
||||
if (!expected.matches(actual)) {
|
||||
return false;
|
||||
}
|
||||
} else if (actual !== expected) {
|
||||
return false;
|
||||
}
|
||||
}
|
||||
return true;
|
||||
},
|
||||
structuralMatcher = <S extends object, T extends S>(
|
||||
shape: S,
|
||||
refine?: (value: S) => value is T,
|
||||
): Matcher<T> => ({
|
||||
matches: (value: unknown): value is T => {
|
||||
if (typeof value !== "object" || value === null) {
|
||||
return false;
|
||||
}
|
||||
// oxlint-disable-next-line typescript/no-unsafe-type-assertion
|
||||
const candidate = value as S;
|
||||
if (!keysMatch(shape, candidate)) {
|
||||
return false;
|
||||
}
|
||||
if (refine && !refine(candidate)) {
|
||||
return false;
|
||||
}
|
||||
return true;
|
||||
},
|
||||
});
|
||||
|
||||
export const P = {
|
||||
literal: literalMatcher,
|
||||
type: typeMatcher,
|
||||
when: whenMatcher,
|
||||
any: whenMatcherAny,
|
||||
shape: structuralMatcher,
|
||||
} as const;
|
||||
|
||||
export type Pattern<T> = Matcher<T>;
|
||||
Reference in new issue
Block a user