fix(jest-mock): remove leftover own accessor when restoring spyOn of an inherited getter/setter#16226
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SimenB merged 5 commits intoJun 21, 2026
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…an inherited getter/setter (jestjs#16226)
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Summary
jest.spyOn(object, key, 'get' | 'set')supports spying on an accessor that lives on the prototype chain rather than on the object itself. When the accessor is inherited, the spy is installed by defining a new own property on the object viaObject.defineProperty(object, propertyKey, descriptor). The restore step then re-defines that same own descriptor on the object instead of removing it.The result is that after
mockRestore, the object keeps an own accessor descriptor that shadows the prototype. The value read right after restore is still correct because the restored descriptor copied the prototype accessor, but the link to the prototype is gone, so later changes to the prototype accessor are no longer observed through the instance, andhasOwnProperty(key)staystrueon something that was originally inherited.The method branch of
spyOnalready handles this correctly: it tracks whether the method was an own property and deletes the own property on restore when it was inherited (see the existingisMethodOwnerhandling and the "should delete previously inexistent methods when restoring" test). This change applies the same approach to the accessor branch in_spyOnProperty: when the spied accessor was inherited, restoring now deletes the own property so the original prototype accessor is exposed again.Test plan
Added two tests under
packages/jest-mock/src/__tests__/index.test.tsin thespyOnPropertyblock, covering an inherited getter and an inherited setter. Each test spies on the inherited accessor, restores, and asserts that no own descriptor is left on the instance and that the prototype accessor is still in effect (including after the prototype accessor is later replaced).Both tests fail on
mainand pass with this change. The fulljest-mockunit suite passes.