mockRestore doesn't restore spied on properties to their original values

[kherock]

Describe the bug

When using vi.spyOn() to create function mocks, the spy.mockRestore(), vi.mockRestoreAllMocks() doesn't actually restore the original descriptor of the spied-on object. This can lead to tests being written without ensuring that a method was already mocked, and deviates from Jest's equivalent behavior.

Reproduction

https://stackblitz.com/edit/vitest-dev-vitest-csdybj?file=test%2Fbasic.test.ts

test('should restore a spy', () => {
  const originalImpl = instance.fn1;
  const spy = vi.spyOn(instance, 'fn1');
  instance.fn1();
  spy.mockRestore();
  expect(instance.fn1).toEqual(originalImpl); // fails
});

test('should fail because it doesn\'t set up a spy', () => {
  instance.fn1();
  expect(instance.fn1).toHaveBeenCalledOnce(); // doesn't throw
});

System Info

System:
    OS: macOS 12.6.3
    CPU: (10) arm64 Apple M1 Pro
    Memory: 88.91 MB / 16.00 GB
    Shell: 5.8.1 - /bin/zsh
  Binaries:
    Node: 16.19.1 - ~/.local/share/homebrew/bin/node
    Yarn: 3.4.1 - ~/.local/share/homebrew/bin/yarn
    npm: 8.19.3 - ~/.local/share/homebrew/bin/npm
  Browsers:
    Firefox: 102.2.0
    Safari: 16.3

envinfo doesn't seem to work with my project's setup (Yarn 3 monorepo), here are my vitest versions:

    "vite": "^4.2.1",
    "vitest": "^0.29.8"

Used Package Manager

yarn

Validations

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• Read the docs.
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• The provided reproduction is a minimal reproducible example of the bug.

[sheremet-va]

This is technically intended behavior. I am not sure if it's the right behavior, but removing a spy breaks module mocking as far as I remember. If someone has time to investigate the consequences of this change, be my guest.

[adrianbienias]

vi.restoreAllMocks docs says

Will call .mockRestore() on all spies. This will clear mock history and reset its implementation to the original one.

For me, it doesn't sound correct - spies aren't reset to the original state, they preserve the mocked one (which is not expected).