2.0.5 breaks module mocking via __mocks__ folder

[EvHaus]

Describe the bug

After upgrading from 2.0.4 to 2.0.5 our tests which rely on module mocking via the __mocks__ folder are now failing with:

Error: ENOENT: no such file or directory, stat '/myproject/__mocks__/index.ts'

Reproduction

To reproduce this, you'll need:

• A __mocks__ folder with the following structure:
  • __mocks__
    • /archiver
      • /index.ts
    • /ora
      • /index.ts
• A test which uses one of the mocked modules (in this case archiver or ora) and calls vi.mock('ora')

It seems like (maybe after #6204) Vitest now expects the __mocks__ folder to have an index.* file, whereas before it wasn't needed.

For a StackBlitz repro see: https://stackblitz.com/edit/vitest-dev-vitest-snzivu?file=package.json,test%2Fbasic.test.ts,src%2Fbasic.ts&initialPath=__vitest__/. Run npm run test to reproduce.

System Info

System:
    OS: macOS 14.6
    CPU: (12) arm64 Apple M2 Max
    Memory: 1.99 GB / 32.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 20.16.0 - ~/.nvm/versions/node/v20.16.0/bin/node
    Yarn: 1.22.19 - ~/.nvm/versions/node/v20.16.0/bin/yarn
    npm: 10.8.1 - ~/.nvm/versions/node/v20.16.0/bin/npm
  Browsers:
    Chrome: 127.0.6533.89
    Chrome Canary: 129.0.6631.0
    Safari: 17.6

Used Package Manager

yarn

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