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fix(spy): fix spyOn types with optional method #7679

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fix(spy): fix spyOn types with optional method #7679

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8dad836
fix(spy): fix spyOn with partial type
hi-ogawa Mar 16, 2025
8304850
test: add confused test
hi-ogawa Mar 16, 2025
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4 changes: 2 additions & 2 deletions packages/spy/src/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -435,8 +435,8 @@ export function spyOn<T, M extends Classes<Required<T>> | Methods<Required<T>>>(
methodName: M
): Required<T>[M] extends { new (...args: infer A): infer R }
? MockInstance<(this: R, ...args: A) => R>
: T[M] extends Procedure
? MockInstance<T[M]>
: Required<T>[M] extends Procedure
? MockInstance<Required<T>[M]>
: never
export function spyOn<T, K extends keyof T>(
obj: T,
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12 changes: 12 additions & 0 deletions test/core/test/jest-mock.test.ts
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Expand Up @@ -608,4 +608,16 @@ describe('jest mock compat layer', () => {
expect(spy.mock.calls).toEqual([])
})
})

it.fails('optional method type', () => {
interface Person {
greet: (name: string) => string
}
const person: Partial<Person> = {}
const spy = vi.spyOn(person, 'greet')
expect(spy).toBe(person.greet)
expect(person.greet?.('Alice')).toMatchInlineSnapshot()
spy.mockImplementation(() => 'mocked')
expect(person.greet?.('Bob')).toMatchInlineSnapshot()
})
})