False negative error: ScopeMismatch must not be raised for Factories as fixtures used in fixtures with a higher scope

[simon-liebehenschel]

Problem explanation

ScopeMismatch must not be raised for Factories as fixtures used in fixtures with a higher scope. I am forced to set scope="module" for my factories, but this is nonsense: factories always return a new value. In general, setting any scope for a factory use redundant and unnecessary: scope affects nothing for factories as fixtures. Please correct me if I am wrong.

Expected behavior

Allow writing factories as fixtures without scope and use them in fixtures with any scope.

Sample failing code:

import random

import pytest


@pytest.fixture()
def make_customer_record():
    def _make_customer_record():
        return {"name": random.random(), "orders": []}

    return _make_customer_record


@pytest.fixture(autouse=True, scope="module")
def create_customers(make_customer_record) -> None:
    customer_1 = make_customer_record()
    customer_2 = make_customer_record()
    customer_3 = make_customer_record()
    print(f"\n{customer_1}, {customer_2}, {customer_3}")


def test_customers():
    ...

Sample working code:

The same as above, but set scope for the factory fixture:

@pytest.fixture(scope="module")` 
def make_customer_record():

Versions

Pytest: 6.2.5
Python: 3.9
OS: Lubuntu 20.04

[asottile]

the scope mismatch error looks correct to me, you have a module scoped fixture is requesting a function scoped fixture -- the lifetimes would mismatch (fixtures must only request equal or greater scopes)

you should adjust your make_customer_record fixture to be either scope='session' or scope='module'

[nicoddemus]

To complement:

The default scope is function, so the mismatch is correct as @asottile commented.

Allow writing factories as fixtures without scope and use them in fixtures with any scope.

Yes those are what we called invocation scoped fixtures however at the time we couldn't really ship them.