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E721: pycodestyle v2.11.0 does not raise the error to `int == type(obj)`

Aperta
  • Qualcosa non va?
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Valutazione

Difficoltà
2/5
Tempo stimato
1-3 ore
Idoneità per principianti
48/100
Tipo di issue
Bug
Chiarezza
Specificata chiaramente
Stato di attività
Ferma
Stack tecnologico
python
Ambito
tooling

Direzione di ricerca

Inizia in pycodestyle.py con COMPARE_TYPE_REGEX e comparison_type, quindi riproduci entrambe le forme di confronto usando i comandi mostrati nell’issue. Modifica la gestione in modo che int == type(obj) generi E721, mentre il comportamento esistente di type(obj) == int rimanga corretto, e verifica entrambi i casi con pycodestyle.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

Environment
% python -V
Python 3.11.4
% pycodestyle --version
2.11.0

% pip list
Package     Version
----------- -------
pip         23.2.1
pycodestyle 2.11.0
setuptools  68.0.0
Normal behavior
% cat example.py
if type(obj) == int:
    pass
% pycodestyle example.py
example.py:1:4: E721 do not compare types, for exact checks use `is` / `is not`, for instance checks use `isinstance()`

Great!

Strange behavior

Change type(obj) == int to int == type(obj) (swap the left and right sides).

Expected

Raise E721.
This code is still comparing the return value of type.

Actual

Do NOT raise E721.

% cat example.py
if int == type(obj):
    pass
% pycodestyle example.py
% echo $?
0
Investigation
>>> from pycodestyle import comparison_type
>>> list(comparison_type("if type(obj) == int:", noqa=False))
[(3, 'E721 do not compare types, for exact checks use `is` / `is not`, for instance checks use `isinstance()`')]
>>> list(comparison_type("if int == type(obj):", noqa=False))
[]

In v2.11.0 (21abd9b6dcbfa38635bc85a2c2327ec11ad91ffc), COMPARE_TYPE_REGEX has 2 captures.
https://github.com/PyCQA/pycodestyle/blob/21abd9b6dcbfa38635bc85a2c2327ec11ad91ffc/pycodestyle.py#L128-L131

In comparison_type, the first captured substring is only referred (inst = match.group(1)).
https://github.com/PyCQA/pycodestyle/blob/21abd9b6dcbfa38635bc85a2c2327ec11ad91ffc/pycodestyle.py#L1451-L1452
https://github.com/PyCQA/pycodestyle/blob/21abd9b6dcbfa38635bc85a2c2327ec11ad91ffc/pycodestyle.py#L1461-L1470

>>> from pycodestyle import COMPARE_TYPE_REGEX
>>> from pycodestyle import SINGLETONS

>>> match = COMPARE_TYPE_REGEX.search("if type(obj) == int:")
>>> match
<re.Match object; span=(3, 15), match='type(obj) =='>
>>> match.group(1)  # None; Go yield (L1466)
>>> match.group(2)
'obj'

>>> match = COMPARE_TYPE_REGEX.search("if int == type(obj):")
>>> match
<re.Match object; span=(7, 19), match='== type(obj)'>
>>> match.group(1)
'obj'
>>> match.group(2)
>>> inst = match.group(1)
>>> inst and inst.isidentifier() and inst not in SINGLETONS  # Go return (L1465) not yield
True

If you need to use captured substrings, you might need to do something like inst = match.group(1) or match.group(2).
However, in that case, inst and inst.isidentifier() and inst not in SINGLETONS would return True, and E721 would no longer be raised.
Therefore, I believe that removing the return statement here would resolve the reported issue.

One concern I have is that it seems inst = match.group(1) has not been changed along with the last pull request.
https://github.com/PyCQA/pycodestyle/pull/1086/files
Depending on the reason for not changing this, we might need to consider a different solution.

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