Add new check "implicit-flag-alias"

[jayaddison]

Type of Changes

	Type
✓	✨ New feature

Description

This changeset implements an implicit-flag-alias check that inspects classes derived from enum.Flag and looks for member values that share common bit positions.

The commented sample code below may help explain:

from enum import IntFlag

class Test(IntFlag):

    # valid cases:

    A = 1
    B = 2
    C = 2          # C is an alias (alternative name) for B, and is not highlighted by the check
    D = A | B      # D shares bit positions with A and B, but uses bitwise-operator syntax and is not highlighted

    # implicit-flag-alias cases:

    E = 3          # The value of E shares bit positions with A and B, so the check will highlight it

Closes #8102.
Replaces and continues from #8105 (origin branch accidentally deleted).

[codecov]

Codecov Report

Merging #8345 (1fc1eac) into main (bd3bcb1) will increase coverage by 0.00%.
The diff coverage is 100.00%.

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #8345    +/-   ##
========================================
  Coverage   95.46%   95.47%            
========================================
  Files         176      177     +1     
  Lines       18543    18726   +183     
========================================
+ Hits        17702    17878   +176     
- Misses        841      848     +7     

Impacted Files	Coverage Δ
pylint/checkers/classes/class_checker.py	93.71% <100.00%> (+0.14%)	⬆️
pylint/testutils/_primer/package_to_lint.py	76.81% <0.00%> (-23.19%)	⬇️
pylint/testutils/reporter_for_tests.py	93.02% <0.00%> (-0.32%)	⬇️
pylint/checkers/variables.py	97.30% <0.00%> (-0.08%)	⬇️
pylint/checkers/base/basic_error_checker.py	95.51% <0.00%> (-0.04%)	⬇️
pylint/checkers/base/basic_checker.py	97.87% <0.00%> (-0.03%)	⬇️
pylint/lint/run.py	86.36% <0.00%> (ø)
pylint/constants.py	100.00% <0.00%> (ø)
pylint/reporters/text.py	87.05% <0.00%> (ø)
pylint/checkers/stdlib.py	96.70% <0.00%> (ø)
... and 32 more

[jayaddison]

Thanks again @Pierre-Sassoulas :)

[github-actions]

🤖 According to the primer, this change has no effect on the checked open source code. 🤖🎉

This comment was generated for commit 1fc1eac

[jayaddison]

Checking in to confirm that this looks like it's working as expected in v2.17.0 - I'll watch for any unexpected issues and/or false positives.

Tested with v2.17.0:

# flag-overlap.py
from enum import IntFlag

class Chroma(IntFlag):
    BLEU = 0
    RED = 1
    BLEU = 2
    GRÜNE = 3
    黄色 = 4

$ pylint flag-overlap.py 
************* Module flag-overlap
flag-overlap.py:7:4: W0213: Flag member <Chroma.GRÜNE: 3> shares bit positions with <Chroma.RED: 1> (3 & 1 = 1), <Chroma.BLEU: 2> (3 & 2 = 2) (implicit-flag-alias)
flag-overlap.py:7:4: C2401: Attribute name "GRÜNE" contains a non-ASCII character, consider renaming it. (non-ascii-name)
flag-overlap.py:8:4: C2401: Attribute name "黄色" contains a non-ASCII character, consider renaming it. (non-ascii-name)

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Your code has been rated at 5.71/10 (previous run: 7.14/10, -1.43)