tmu
52ce655d8e
test:ci now runs c8 with --all --include "src/**/*.ts" --100, so the build job fails when any runtime file under src/ is untested. --all is what makes the gate non-vacuous: without it c8 counts only the files the suite happened to load, and a new untested module stays invisible. Add src/index.test.ts to load the public barrel, which was previously never imported at runtime and so read as 0% under --all. matcher-shared.ts is types-only (an empty runtime image) and carries a file-level c8 ignore with the reason. Why 100% and the rejected alternatives: development/ci.md § Coverage threshold.
tiny-pattern-ts
Pattern matching for TypeScript/ESM environments (F#-style, not regex).
Description
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
for the design decisions and Caveats for the limits.
Requirements
- Node.js >= 26 (
enginesfield; pinned via.node-version). - TypeScript >= 5.0 to consume the published declarations. The emitted
.d.tsuseconsttype parameters (TS 5.0) and keep their relative.tsspecifiers; both resolve on TS >= 5.0 innode10/node16/nodenext/bundler. - The package is ESM-only (no CommonJS shim).
API
Yet to be implemented
Caveats
- Only finite universes are supported. The factory must be given a finite
union of literals;
string,numberand template literals are rejected. This is what lets the exhaustive overload be proven, so the runtimedispatchthrow stays unreachable through the typed API. - A value and its stringification must not both be present. Object keys
stringify, so a universe containing both a member and the string it
stringifies to —
1 | "1",true | "true",null | "null"— is rejected at the factory. Either form alone is fine, and one value's string form may coexist with a different value's bare form ("true" | false). symbolandbigintare not supported. Asymbolbrand is a compile-time phantom with nothing to match at runtime, and abigintis not a valid property key; neither satisfies the matcher's universe constraint.NaNand-0cannot be matched specifically. They have no literal type, so both stay part ofnumber.
Why open universes are rejected
An open universe — one carrying a broad member, as in
type Units = "s" | "ms" | "min" | (string & {}) — is not a dispatch concern.
If the values arrive from outside the program, parse them at the boundary down
to a finite union and match the narrowed result; the openness never reaches the
matcher. If the domain is genuinely extensible, the right shape is a runtime
Map of handlers, where "no handler" is a lookup, not a pattern. Either way an
open matcher would abandon the one guarantee this library exists to give —
provable exhaustiveness — to automate what a switch and a default arm already
cover. The type-level cost of supporting open universes is recorded in
development/library.md.
License
MIT © 2025 tmu. See LICENSE.
Contributing
Contributions are documented in CONTRIBUTING.md; the reasons behind the project's decisions, rejected alternatives, and known issues live in development/. AI coding agents start at AGENTS.md.