fix!(spy): align mocking related typings with jest

[hi-ogawa]

Description

Closes #4723

I started with a mostly straight-forward typing update by following jestjs/jest#12489. I will consider the implication of this change in details later.

todo

• user-land workaround 4723#issuecomment-1863740082
• remove deprecated SpyInstance?
• should vi.fn default to (...args: any[]) => any or (...args: unknown[]) => unknown?
• more type tests
• doc / migration guide

references

• refactor(jest-mock)!: simplify usage of jest.fn generic type arguments jestjs/jest#12489
• refactor(jest-mock)!: rework Mocked* utility types jestjs/jest#13123
• refactor(jest-mock)!: change the default jest.mocked helper’s behaviour to deep mocked jestjs/jest#13125
• feat(@jest/globals, jest-mock): add jest.Spied* utility types jestjs/jest#13440

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[sheremet-va]

I don't think we should change base types yet. Instead, I propose defining a namespace with new mock types like vite does with Rollup namespace (naming can be discussed):

// mock-types.ts
export type MockContext<T extends Procedure> = {}

// spy.ts
import type * as Mocks from './mock-types.ts'
export type { Mocks }

// test.ts
import type { Mocks } from 'vitest'
const fn: Mocks.Spy<() => void> = vi.fn()

[hi-ogawa]

SpyInstance is deprecated, so can we remove it in v2 with this change?

vitest/packages/spy/src/index.ts

Lines 111 to 114 in c17bac0

	/**
	* @deprecated Use MockInstance<A, R> instead
	*/
	export interface SpyInstance<TArgs extends any[] = any[], TReturns = any> extends MockInstance<(...args: TArgs) => TReturns> {}

[sheremet-va]

SpyInstance is deprecated, so can we remove it in v2 with this change?

Sure, let's remove it.

[hi-ogawa]

I took the latter one to follow Jest for now, but I think going with the former should be totally fine too.
Jest one is technically type unsafe and the assignment example I wrote here can be easily rewritten by:

jest.fn<() => boolean>(() => true)
jest.fn(() => true as boolean)

Or in a more realistic scenario, it would probably look like:

// setup
type MyFn = () => boolean;
let myMockFn: Mock<MyFn>

// test
myMockFn = vi.fn<MyFn>(() => true)