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flow-typed/jest.js is hand-maintained, so it drifted from the Jest API: it was missing getMockImplementation() until react#2163, and the missing declaration surfaced only as an internal Flow error, hidden in OSS behind $FlowFixMe[prop-missing]. scripts/__tests__/checkJestLibdef-test.js fails when a jest-mock MockInstance method is missing from JestMockFn, so the next omission fails OSS CI instead. It brings the libdef up to date first, adding getMockName() and withImplementation().
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November 3, 2026 20:16
Extract MockInstance members with the TypeScript compiler API and JestMockFn members with flow-parser, instead of brace counting and regexes over source text.
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Dropping this: the check is too specific and sketchy. The libdef additions (getMockName, withImplementation) go with it; getMockImplementation stays via #2163. |
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flow-typed/jest.js is hand-maintained, so it drifted from the Jest API: it was missing getMockImplementation() until #2163, and the missing declaration surfaced only as an internal Flow error, hidden in OSS behind $FlowFixMe[prop-missing].
scripts/tests/checkJestLibdef-test.js fails when a jest-mock MockInstance method is missing from JestMockFn, comparing against the jest-mock types pinned in node_modules (jest-mock internals _isMockFunction / _protoImpl are intentionally excluded). The next omission fails OSS CI instead of internal Flow. Member extraction uses the TypeScript compiler API for the .d.ts side and flow-parser for the Flow side, not regexes over source text.
Generating flow-typed/jest.js from the TypeScript definitions was evaluated and is not viable: flowgen 1.21.0 crashes on jest-mock's own index.d.ts (TypeError in its printer), and the file also covers more than jest-mock (expect, test, fake timers) from several sources, so there is no single TS source to generate it from. flow-api-translator in this repo goes the other direction (Flow to TS).
It brings the libdef up to date first, adding getMockName() and withImplementation().
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