Hypothesis fixture scope warning does not detect if fixture is overridden

[simonfagerholm]

In #2356 a warning was added if @given() is used together with function scoped fixtures.
However the warning functionality does not discover if a fixture is overridden by a "closer" definition, e.g. if a fixture with the same name is defined in the test file. See image below of how fx_defs looks with multiple definitions.

This was discovered while fixing pytest-dev/pytest-asyncio#145.

@Zac-HD: Do you have any ideas?

[Zac-HD]

This might be as simple as reversing our iteration order, or we might need to do something a little fancier...

We also need to add tests for cases where a function-scoped fixture is overridden with a safe scope, and vice-versa!

[simonfagerholm]

@Zac-HD: I did a quick test and this approach seems to work at least in this case:

for fx in fx_defs:
    fxture = item._request._get_active_fixturedef(fx.argname)
    if fxture.scope == "function":
        note_deprecation(
            "%s uses the %r fixture, but function-scoped fixtures "
            "should not be used with @given(...) tests, because "
            "fixtures are not reset between generated examples!"
            % (item.nodeid, fx.argname),
            since="2020-02-29",
        )

I used the internal _get_active_fixturedef to get the same fixture that pytest is using for this item. I figured this might be better than guessing pytests approach to order fixtures, but it might have other problems.

[simonfagerholm]

Maybe this is better to prevent initializing fixtures that are not being used:

if fx.argname in argnames:
    fxture = item._request._get_active_fixturedef(
        fx.argname)
    if fxture.scope == "function":
        note_deprecation(
            "%s uses the %r fixture, but function-scoped"
            " fixtures should not be used with @given(...)"
            " tests, because fixtures are not reset "
            "between generated examples!"
            % (item.nodeid, fx.argname),
            since="2020-02-29",
        )

[Zac-HD]

That looks great to me - want to open a PR?

[simonfagerholm]

@Zac-HD Sure, I will get on it

[Zac-HD]

Closed by #2376.