Jest: Namespace undefined when using jest.mock()

[andreabosman16]

🐛 Bug Report

When using jest.mock("fs") and the new promise namespace inside of it. the mock doesn't contain the promise namespace.

To Reproduce

Steps to reproduce the behavior:
- Write code with fs.promise.function.
- Write test with import fs and mock fs.

Expected behavior

I except that the promise namespace is usable when fs is mocked.

[SimenB]

I _think_ this is due to us not following getters. The reasoning is that getters are functions, so accessing them can throw. I'm not sure how to deal with this

[doniyor2109]

Maybe we can simply access getters too and when there are some errors, then simply show proper error message for that cases?

[SimenB]

Do we want to error, though?

I guess we could define our own getters and dynamically call the underlying ones to figure out their type. If they throw, ask users to mock it manually?

jest.mock('thing', () => ({
  ...jest.genMockFromModule('thing'),
  duynamicThing: jest.fn(),
}));

What if the getter triggers a side-effect, though? We don't invoke functions we just check _if_ they're functions.

Maybe we can always throw inside getters asking people to mock it manually since Jest was unable to figure out its type? Not sure.

[doniyor2109]

I forgot about side effects.

[doniyor2109]

Is it possible to return Proxy for that cases. As we cannot access getters then maybe Proxy allows to act as any shaped mocks?

[andreabosman16]

I fixed the problem with fs.promises.function = jest.fn() for the time being.
Hopefully this issue will get fixed.