B038 false positive in 24.1.15 + 24.1.16

[mikaelarguedas]

First of all thanks for this new B038 new rule, it's a great addition!

Using flake8-bugbear 24.1.15

The following code is flagged.

some_list = [1, 2, 3]
for elem in some_list:
    print(elem)
    if elem == 2:
        found_idx = some_list.index(elem)  # should not error
        break

Although a method of some_list is called I believe this doesn't have any effect on the mutable

[mikaelarguedas]

cc @mimre25 for feedback on this as it may also impact the ruff implementation

[wxtim]

Looks similar to

mydicts = {'a': {'foo': 1, 'bar': 2}}

for mydict in mydicts:
    if mydicts.get('a', ''):
        print(mydict['foo'])

B038 is complaining about any instance of an object method called inside the loop that object is the iterator for, without checking whether the loop is modifying it.

[cooperlees]

Agree this looks a bad / annoying false positive. Will take a fix for this asap and release.

Thanks for reporting.

[mimre25]

Oh snap, I actually ran this on a quite big code-base as a test and I didn't have any false positives reported.

I'll take a look and see if I can fix this.

Thanks for reporting this and tagging me :slightly_smiling_face:

[Skrethel]

I've also encountered this false positive for copy() function

d = {}
for _ in d:
    copied = d.copy()