extend C1802 to detect len() comparisons with zero #10658
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Add detection for len() comparisons with 0/1 that can be simplified: - len(x) == 0 → not x - len(x) > 0 → x (or bool(x)) - len(x) != 0 → x (or bool(x)) - Reversed operands: 0 == len(x), etc. Implementation: - Add _check_len_comparison_with_zero() method - Add _get_len_comparison_suggestion() for context-aware suggestions - Reuse existing inference and boolean context detection - Handle edge cases: chained comparisons, custom __bool__
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- Added logic to identify when len() comparisons are nested within boolean operations or are directly returned.
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| self._check_compare_to_str_or_zero(node) | ||
| if self.linter.is_message_enabled("use-implicit-booleaness-not-len"): | ||
| self._check_len_comparison_with_zero(node) |
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It seems highly likely that optimization or code deduplication can be found by re-using check_compare_to_str_or_zero here.
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From what i understood i have added _extract_comparison_operands() helper method that both _check_compare_to_str_or_zero() and _check_len_comparison_with_zero() now use.
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I have issued new commits resolving this
| if True or len('TEST'): # [use-implicit-booleaness-not-len] | ||
| pass | ||
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| if len('TEST') == 0: # Should be fine |
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I think we need to check the initial reasoning for this before changing, I didn't have this context when labelling the initial issue a false negative.
Pierre-Sassoulas
added
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False Negative 🦋
Codecov Report❌ Patch coverage is
❌ Your patch check has failed because the patch coverage (94.11%) is below the target coverage (100.00%). You can increase the patch coverage or adjust the target coverage. Additional details and impacted files@@ Coverage Diff @@
## main #10658 +/- ##
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- Coverage 95.96% 95.96% -0.01%
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Files 176 176
Lines 19502 19604 +102
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+ Hits 18715 18812 +97
- Misses 787 792 +5
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…th 0 - Add detection for len(iterable) == 0, != 0, > 0, >= 0, < 1, <= 0 patterns - Support reversed operands (0 == len(x), 0 < len(x), etc.) - Extract _extract_comparison_operands() helper to reduce code duplication - Fix critical bug in constant-on-left comparison logic (1 <= len(x) was wrong) - Add comprehensive test coverage for edge cases - Update documentation with new pattern examples - Fix too-many-returns linting issue by consolidating logic - All tests passing, 100% coverage for new functionality
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Description
This PR extends the
use-implicit-booleaness-not-len(C1802) checker to detect additional patterns wherelen()is compared against zero or one, enabling more comprehensive detection of implicit booleaness violations.Changes Made
Core Implementation (
pylint/checkers/refactoring/implicit_booleaness_checker.py):_check_len_comparison_with_zero()method to detectlen()comparisons with constants_get_len_comparison_suggestion()helper for context-aware suggestion generationvisit_compare()to call the new detection logicuse-set-for-membershipandno-else-returnwarningsTest Updates:
tests/functional/u/use/use_implicit_booleaness_not_len.pywith new test casestests/functional/u/use/use_implicit_booleaness_not_len.txtwith expected violationsNew Detection Patterns
The checker now catches these previously missed patterns:
This enhancement significantly improves pylint's ability to catch implicit booleaness violations while maintaining the checker's existing behavior and performance characteristics.
Closes #10281