Dynamically imported mocks are initiated multiple times

[christian-bromann]

Describe the bug

Given a module that imports a package dynamically, e.g.:

export default async () => {
  const id = 'a-vitest-test-modulea';
  return (await import(id)).default();
};

If I define a-vitest-test-modulea as a mock via:

vi.mock('a-vitest-test-modulea', () => {
  console.log('INITIALIZE MOCK');
  return {
    default: vi.fn().mockReturnValue('I am mocked'),
  };
});

then the mock gets initialised multiple times - one time when my actual source file imports it and the other when my test imports it so I can make assertions - which makes it impossible to run e.g. toBeCalledTimes assertions. This is working in Jest as expected.

Reproduction

https://stackblitz.com/edit/vitest-dev-vitest-payj4m?file=src%2Findex.ts,test%2Fbasic.test.ts&initialPath=__vitest__

System Info

System:
    OS: Linux 5.16 Ubuntu 20.04.4 LTS (Focal Fossa)
    CPU: (16) x64 AMD EPYC 7B13
    Memory: 31.36 GB / 62.80 GB
    Container: Yes
    Shell: 5.8 - /usr/bin/zsh
  Binaries:
    Node: 18.4.0 - ~/.nvm/versions/node/v18.4.0/bin/node
    Yarn: 1.22.19 - ~/.nvm/versions/node/v18.4.0/bin/yarn
    npm: 8.12.1 - ~/.nvm/versions/node/v18.4.0/bin/npm
  Browsers:
    Chrome: 101.0.4951.64
  npmPackages:
    vitest: ^0.16.0 => 0.16.0

Used Package Manager

npm

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

[christian-bromann]

Note: when modifying the module to import a string rather than a variable, the behavior is expected:

export default async () => {
  // this way it works
  return (await import('a-vitest-test-modulea')).default();
  // this way it doesn't
  const id = 'a-vitest-test-modulea';
  return (await import(id)).default();
};