gh-156515: Correctly filter conditional annotations in FORWARDREF and STRING formats

[JelleZijlstra]

• Issue: Conditional annotations are always included in STRING annotations #156515

[DavidCEllis]

This seems to do the right thing.

Testing-wise I don't think the Format.FORWARDREF case you have is doing anything? In both the VALUE and FORWARDREF cases it's going through _get_dunder_annotations which will succeed.

If you want a FORWARDREF case that fails on main this should work:

class ConditionalForwardRef:
    a: object.undefined
    if False:
        b: str

get_annotations(ConditionalForwardRef, format=Format.FORWARDREF)

I think a case with a: undefined would test a different branch, although that already succeeds on main.