E721: flag swapped type comparisons like int == type(obj)#1317
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apoorvdarshan wants to merge 1 commit into
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E721: flag swapped type comparisons like int == type(obj)#1317apoorvdarshan wants to merge 1 commit into
int == type(obj)#1317apoorvdarshan wants to merge 1 commit into
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E721 only fired when a `type(...)` call was on the left-hand side of `==` / `!=` (e.g. `type(obj) == int`). The swapped form `int == type(obj)` was silently ignored even though it is the same type comparison. `comparison_type` only inspected `match.group(1)`, the argument of the right-hand `type(...)` call, and suppressed the warning whenever that argument was a plain identifier. Because the two regex alternatives capture opposite sides, this made the check asymmetric: `type(obj) == x` was reported but the mirror `x == type(obj)` was not. Remove the identifier-based suppression so both operand orders are treated identically, and drop the now-unused capture groups from COMPARE_TYPE_REGEX. Add regression fixtures for the swapped `==` and `!=` forms to testing/data/E72.py. Fixes PyCQA#1187.
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Summary
E721 (
do not compare types) only fired when atype(...)call appeared on the left of==/!=:comparison_typeinspected onlymatch.group(1)— the argument of the right-handtype(...)call — and suppressed the warning whenever that argument was a plain identifier (if inst and inst.isidentifier() and inst not in SINGLETONS: return). Because the two alternatives ofCOMPARE_TYPE_REGEXcapture opposite operands, this made the check asymmetric:type(obj) == xwas reported while the mirrorx == type(obj)was not, and the issue'sint == type(obj)slipped through entirely.Fix
Remove the identifier-based suppression so both operand orders are treated identically, and drop the now-unused capture groups from
COMPARE_TYPE_REGEX(they are no longer referenced). The regex already matches a baretype(...)call on either side of==/!=, so the check is now symmetric.No existing
Okayfixture relied on the suppression — every one of them fails to matchCOMPARE_TYPE_REGEXin the first place (they useis/is not,.type(,compute_type(, ortypes.SomeType), so those cases are unaffected.Tests / Verification
testing/data/E72.pyfor the swapped==and!=forms (if int == type(res):,if str != type(res):), each annotated#: E721. These fail on the pristine code and pass with the fix.E721doctest examples to thecomparison_typedocstring (verified bytests/test_self_doctests.py).pytest tests/— all 777 tests pass.pytest tests/test_data.py -k E72— 26 fixture cases pass.pre-commit run --files pycodestyle.py testing/data/E72.py— all hooks (flake8, pyupgrade, reorder-python-imports, etc.) pass.tests/test_all.py) passes; running the CLI on the issue's repro now emitsE721.Fixes #1187.
Disclosure: prepared with AI assistance; reviewed and verified locally.