feat: return a disposable from doMock()

[kirkwaiblinger]

Description

This makes doMock() return a disposable that calls the corresponding doUnmock() upon being disposed.

Resolves #8425

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[sheremet-va]

This test seems weird, because Symbol.dispose in _incrementMock?.[Symbol.dispose] is always undefined and test always checks for _incrementMock[undefined]

Maybe it should instead check Object.keys(_incrementMock)

[kirkwaiblinger]

I had lifted the pattern from here:

vitest/test/core/test/jest-mock.test.ts

Lines 758 to 762 in d3afa60

	describe.skipIf(Symbol.dispose)('in environments not supporting it', () => {
	it('does not have dispose property', () => {
	expect(vi.fn()[Symbol.dispose]).toBeUndefined()
	})
	})

I wasn't sure if Symbol.dispose was patched in between evaluating the skipIf condition and the test body or something, for example, by something like

vitest/test/core/test/esnext.test.ts

Line 22 in e922e92

Symbol.dispose ??= Symbol('dispose')

---

If Symbol.dispose really is undefined, then maybe we just skip the test altogether? There are already tests that assert that doMock()'s functionality works, so it doesn't really matter what the return value is in a non-using-supporting environment 🤷 Or, like you say, we could examine the keys of the object, but it's just a little weird to try to do that when we can't name the key that we're interested in.

[sheremet-va]

Sure, if there is no reason to test something, then don't test it