[LuisFigueroaG]

B911 treats every bare batched() call as itertools.batched. Projects that still support Python < 3.12 often ship their own backport, which has no strict parameter, and they get B911 on every call:

# fontTools/misc/iterTools.py
def batched(iterable, n): ...

# fontTools/ttLib/scaleUpem.py
from fontTools.misc.iterTools import batched

for batch in batched(items, 2):  # B911, but this batched() takes no strict=
    ...

B031 already handles the same thing for groupby() (#356): a bare groupby only counts as itertools when the module imports it from itertools or doesn't bind the name at all. This turns that helper into one that takes the name, and B911 now uses it for batched. It also recognises batched = itertools.batched assignments (including inside try/except), which B031 gets for groupby as well. Some things are still reported:

• itertools.batched(...) calls.
• from itertools import batched and from itertools import *.
• A try: from itertools import batched / except ImportError: def batched(...) fallback, since on newer Pythons the name really is itertools.batched.
• batched = itertools.batched, also as a try/except AttributeError fallback.

On about 48,000 files (site-packages from eight project virtualenvs, Ubuntu's Python 3.12 stdlib and the repos in my workspace), B911 reports drop from 30 to 4 and B031 stays at 14. Nothing new is reported. The 26 removed reports come from three sources, each installed in several venvs: fontTools (backport with no strict), blosc2 (batched imported from its own proxy_source backport) and the copy of more_itertools vendored in setuptools, which defines its own batched wrapper.

New cases are in tests/eval_files/b911_shadowed*.py and tests/eval_files/b031_shadowed_alias.py. Three of them fail on main (the B911 alias cases pass there and guard the regression). tox py310–py315, mypy and pep8_naming pass, and so does pre-commit.

[Copilot]

🟡 Changes recommended

The guard incorrectly suppresses B911 diagnostics for assignment-based itertools.batched aliases, including try/except fallbacks, requiring a fix and regression coverage that preserves B031 behavior.

1 open issue

• Recognize assignment-based itertools aliases for B911 · New

What changed in this PR

This PR reduces B911 false positives for custom batched() implementations by reusing B031’s module-level binding check.

Changes:

• Generalizes the itertools name resolver and its cache for use by B031 and B911.
• Adds regression cases for local definitions, third-party imports, and import fallbacks.
• Documents the B911 behavior change in the unreleased changelog.

File	Description
tests/​eval_files/​b911_shadowed.py	Covers a locally defined batched and a qualified itertools call.
tests/​eval_files/​b911_shadowed_import.py	Covers a third-party batched import.
tests/​eval_files/​b911_shadowed_fallback.py	Keeps B911 reporting for an itertools import with a backport fallback.
README.rst	Adds the B911 changelog entry.
bugbear.py	Shares itertools binding resolution between B031 and B911.

_{Review effort: Balanced}

[LuisFigueroaG]

Good catch, fixed: batched = itertools.batched (also inside a try/except fallback) now counts as itertools again, with new eval files for both. B031 gets the same through the shared helper, so groupby = itertools.groupby is now covered too.

[cooperlees]

Thanks again!