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….333 Summary: `flow-api-translator` 0.332.0 translates `declare module.exports` to TypeScript's `export =` (facebook/flow#9491). Until now `scripts/generateTypeScriptDefinitions.js` rejected any module whose Flow def used it, which is why all of `metro-runtime` bar `modules/types.js` was excluded, and why most of our hand-maintained `src/**/*.d.ts` overrides exist. With `flow-api-translator` on 0.333.0, this drops the `module.exports` rejection and the `metro-runtime` exclusion, and removes as many overrides as the translator can now replace: - `metro-runtime` is generated like any other package - `asyncRequire`, `HMRClient`, `null-module` and `polyfills/require` gain types and API snapshots. - Eight overrides go: `metro-minify-terser` and `metro-symbolicate` (generated output is equivalent), the five CommonJS worker and extractor modules in `metro-file-map`, and `metro-file-map/src/lib/dependencyExtractor.d.ts`, which had no `.js` beside it and so was never used. - Two stay: `metro-transform-plugins/src/index.d.ts`, because it combines `export type` with `module.exports`, which TypeScript can't express as `export =` without namespace merging; and `crawlers/watchman/planQuery.d.ts`, because the generated output imports types from `fb-watchman`, which has none. Getting there needed a few changes to the generator and to Flow sources, none of which affect runtime behaviour: - Flow comment types (`/*: T */`, `/*:: ... */`) are expanded before translation. The `metro-file-map` workers are loaded in Node without Babel and are typed that way, so the translator saw no annotations at all and emitted `any`. - A `.js.flow` file is used as the Flow source for the adjacent `.js`. That's Flow's own convention, and it types the vendored `eventemitter3` (no `@flow` directive) without an override. - `lintText` returns no result for a path `.eslintignore` covers (`**/vendor/**`), so the generator tolerates that and leaves the output unlinted. - The two `metro-file-map` plugin workers now declare their class and export it by name, rather than exporting an anonymous class expression, which `flowToFlowDef` can't type. - `asyncRequire` exports through an `as AsyncRequire` cast - `flowToFlowDef` drops statics assigned to a function, so `prefetch` and `unstable_importMaybeSync` were otherwise lost. The cast is type-only, and `metro-runtime` already uses `as` casts elsewhere. - `HMRClient._heartbeatTimer` is typed `?ReturnType<typeof setInterval>` in place of Flow's `IntervalID` global, which the translator passes through and TypeScript has no name for. - Generated `.d.ts` no longer run `@typescript-eslint`'s `no-explicit-any` or `no-unused-vars`. Flow checks the sources these are translated from, and an `any` in the output reflects one there; the second rule reports a declaration a CommonJS module exports via `typeof` as unused, which is most of what `metro-runtime` and the `metro-file-map` workers now emit. `no-unused-vars` stays on in the generator's own `--fix` pass, which uses it to drop declarations left unused by translation. `no-empty-object-type` is off too, for now: Flow's inexact `{...}` translates to `{}`, which the rule flags in `polyfills/require.d.ts` - the follow-up diff fixes those annotations at source and turns the rule back on. This replaces the per-file exemption for `metro-file-map/types/flow-types.d.ts`. Changelog: ``` - **[Types]**: Add TypeScript definitions for `metro-runtime` modules, and generate (rather than hand-maintain) types for `metro-file-map` workers ``` Test plan: ``` yarn flow check yarn typecheck-ts yarn build-api-snapshots yarn verify-api-snapshots yarn jest ``` Flow and `tsc` are clean. API snapshots for ES module entry points are unchanged, so removing the overrides changes no public API. `metro-runtime` gains four snapshots, and `metro-minify-terser`'s now reflects its generated definition. Jest: all 150 suites pass, including the `metro` integration tests, which bundle `metro-runtime`.
robhogan
removed this pull request from stack #1997
September 29, 2026 15:13
robhogan
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robhogan
added this pull request to stack #1999
September 29, 2026 15:13
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flow-api-translator0.332.0 translatesdeclare module.exportsto TypeScript'sexport =(facebook/flow#9491). Until now our.d.tsgenerator rejected any module that used it, which is why nearly all ofmetro-runtimewas excluded, and why most of our hand-written.d.tsoverrides exist.With the
flow-*packages on 0.333.0, this generatesmetro-runtimelike any other package, and removes eight overrides the translator now replaces -metro-minify-terser,metro-symbolicateand six inmetro-file-map(one of which had no.jsbeside it, so was never used).Getting there took a few generator changes, and some light-touch changes to Flow source that don't affect runtime:
/*: T */,/*:: ... */) are expanded before translation, because themetro-file-mapworkers run in Node without Babel. It's a regex, but it seems good enough -flow-parser's WASM build drops Flotate..js.flowis used as the Flow source for an untyped.js, per Flow's own convention. That covers the vendoredeventemitter3.asyncRequireis exported through anas AsyncRequirecast, otherwise translation losesprefetchandunstable_importMaybeSync.Lint on generated
.d.tsis relaxed too:no-unused-varsreports a declaration that a CommonJS module exports viatypeof. It's possible to write Flow that avoids it, but that shouldn't be a concern for Flow authors.no-explicit-any- if one appears, it's because we've already suppressed the equivalent in Flow, so respect that.no-empty-object-typeis more legitimate. Flow's inexact{...}becomes{}, and a follow-up re-enables the rule with better types forrequire.js.Snapshots for the new CommonJS entry points depend on #1988, which teaches API Extractor about
export =.Changelog:
Test plan:
metro-runtimeAPI.md files. Some have messy identifiers, but they effectively capture the public surface..d.tslocally (they're gitignored) and inspect the output.