17324292113

Committed 29 Aug 2025 12:51PM UTC coverage: 99.024% (-1.0%) from 100.0%

Build # 17324292113

Build Type

push

github

Committed by

web-flow

Commit Message

fix: work around `getMockImplementation()` in Vitest (#28)

Ensure that default implementations set via `vi.fn(default_impl)` are used,
even when Vitest forgets they exists, by pulling from tinyspy internals

Run Details

70 of 71 branches covered (98.59%)

Branch coverage included in aggregate %.

9 of 10 new or added lines in 2 files covered. (90.0%)

133 of 134 relevant lines covered (99.25%)

186.78 hits per line

Source File
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88.24

/src/fallback-implementation.ts

import type { AnyCallable, MockInstance } from './types.ts'

/** Get the fallback implementation of a mock if no matching stub is found. */
export const getFallbackImplementation = <TFunc extends AnyCallable>(
  mock: MockInstance<TFunc>,
): TFunc | undefined => {
  return (
    mock.getMockImplementation() ?? getTinyspyInternals(mock)?.getOriginal()
  )
}

/** Internal state from Tinyspy, where a mock's default implementation is stored. */
interface TinyspyInternals<TFunc extends AnyCallable> {
  getOriginal: () => TFunc | undefined
}

/**
 * Get the fallback implementation out of tinyspy internals.
 *
 * This slight hack works around a bug in Vitest <= 3
 * where `getMockImplementation` will return `undefined` after `mockReset`,
 * even if a default implementation is still active.
 * The implementation remains present in tinyspy internal state,
 * which is stored on a Symbol key in the mock object.
 */
const getTinyspyInternals = <TFunc extends AnyCallable>(
  mock: MockInstance<TFunc>,
): TinyspyInternals<TFunc> | undefined => {
  const maybeTinyspy = mock as unknown as Record<PropertyKey, unknown>

  for (const key of Object.getOwnPropertySymbols(maybeTinyspy)) {
    const maybeTinyspyInternals = maybeTinyspy[key]

    if (
      maybeTinyspyInternals &&
      typeof maybeTinyspyInternals === 'object' &&
      'getOriginal' in maybeTinyspyInternals &&
      typeof maybeTinyspyInternals.getOriginal === 'function'
    ) {
      return maybeTinyspyInternals as TinyspyInternals<TFunc>
    }
  }

  return undefined
}

1	import type { AnyCallable, MockInstance } from './types.ts'
2
3	/** Get the fallback implementation of a mock if no matching stub is found. */
4	export const getFallbackImplementation = <TFunc extends AnyCallable>(	27✔
5	mock: MockInstance<TFunc>,
6	): TFunc \| undefined => {
7	return (	306✔
8	mock.getMockImplementation() ?? getTinyspyInternals(mock)?.getOriginal()	585✔
9	)
10	}
11
12	/** Internal state from Tinyspy, where a mock's default implementation is stored. */
13	interface TinyspyInternals<TFunc extends AnyCallable> {
14	getOriginal: () => TFunc \| undefined
15	}
16
17	/**
18	* Get the fallback implementation out of tinyspy internals.
19	*
20	* This slight hack works around a bug in Vitest <= 3
21	* where `getMockImplementation` will return `undefined` after `mockReset`,
22	* even if a default implementation is still active.
23	* The implementation remains present in tinyspy internal state,
24	* which is stored on a Symbol key in the mock object.
25	*/
26	const getTinyspyInternals = <TFunc extends AnyCallable>(	27✔
27	mock: MockInstance<TFunc>,
28	): TinyspyInternals<TFunc> \| undefined => {
29	const maybeTinyspy = mock as unknown as Record<PropertyKey, unknown>	279✔
30
31	for (const key of Object.getOwnPropertySymbols(maybeTinyspy)) {	279✔
32	const maybeTinyspyInternals = maybeTinyspy[key]	279✔
33
34	if (	279!
35	maybeTinyspyInternals &&	1,116✔
36	typeof maybeTinyspyInternals === 'object' &&
37	'getOriginal' in maybeTinyspyInternals &&
38	typeof maybeTinyspyInternals.getOriginal === 'function'
39	) {
40	return maybeTinyspyInternals as TinyspyInternals<TFunc>	279✔
41	}
42	}
43
NEW 44	return undefined	×
45	}

mcous / vitest-when / 17324292113

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