Package imported directly and through dependency results in different instances, breaking equality checks

[joaof9]

Describe the bug

First issue so apologies if I missed something

I'm trying to migrate from jest to vite and ran across this

import { takeLatest, take, call, put } from 'redux-saga/effects';
import { testSaga } from 'redux-saga-test-plan';

function identity() {
  return 'value';
}

function* mainSaga() {
  const action = yield takeLatest('a', identity);
}

describe('saga', () => {
  it('works with unit tests', () => {
    testSaga(mainSaga, 40, 2).next().takeLatest('a', identity).next().isDone();
  });
});

I get

Expected
--------
{
  '@@redux-saga/IO': true,
  combinator: false,
  type: 'FORK',
  payload: {
    context: null,
    fn: [Function: takeLatest], <--- this is the part that fails equality check
    args: [ 'a', [Function: identity] ]
  }
}

Actual
------
{
  '@@redux-saga/IO': true,
  combinator: false,
  type: 'FORK',
  payload: {
    context: null,
    fn: [Function: takeLatest], <--- this is the part that fails equality check
    args: [ 'a', [Function: identity] ]
  }
}

This fails because the takeLatest used and imported here, is not the same as the one imported by the 'redux-saga-test-plan' package when validating the takeLatest() part of the test. However the same test works correctly in jest.

It's also easily noticeable when mocking the dependency ourselves,

vi.mock(import('redux-saga/effects'), async (importOriginal) => {
    const actual = await importOriginal();

    return {
        ...actual,
        takeLatest: () => 'some thing',
    };
});

where we get

Expected
--------
{
  '@@redux-saga/IO': true,
  combinator: false,
  type: 'FORK',
  payload: {
    context: null,
    fn: [Function: takeLatest],
    args: [ 'a', [Function: identity] ]
  }
}

Actual
------
'some thing'

which could maybe be a workaround but it seems vite can't mock dependencies of dependencies correctly? Again, note that mocking this with jest would result in both instances being mocked and the test passing.

Anyway the gist of it seems to be that when some package is imported directly in a test file and from another dependency, it results in two different instances of it, and trying to do some equality check between those two fails.

I have tried adding these packages to inline dependencies, optimizeDeps and other options I've seen around, but nothing seems to work

Reproduction

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

System Info

N/A

Used Package Manager

npm

Validations

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[hi-ogawa]

This fails because the takeLatest used and imported here, is not the same as the one imported by the 'redux-saga-test-plan' package when validating the takeLatest() part of the test.

This is because Vitest picks up redux-saga/effects's module export https://publint.dev/[email protected], but redux-saga-test-plan is cjs only https://publint.dev/[email protected] so it will transitively picks up redux-saga/effects's cjs export.

One workaround is to force using redux-saga/effects's cjs export on Vitest, which might be possible using resolve.alias https://stackblitz.com/edit/vitest-dev-vitest-r9knwr?file=vite.config.ts

You can search for "dual package" to find a similar issue https://github.com/vitest-dev/vitest/issues?q=is%3Aissue+%22dual+package%22+

It's also easily noticeable when mocking the dependency ourselves, ... which could maybe be a workaround but it seems vite can't mock dependencies of dependencies correctly?

vi.mock doesn't work for transitive import of cjs, so the workaround I mentioned above doesn't work either. Probably optimizer.ssr.enabled: true is needed there, but it doesn't look working either, so there might be an issue with vi.mock and optimized deps.