F401: false positive causes NameError

[spaceone]

Summary

ruff 0.14.0 introduced a false-positive for F401 unused-import:

  try:
      import asdfasfd.asdf.sadf
  except ImportError:
      import argparse
      import asdfasfd  # W: `asdfasfd` imported but unused
      asdfasfd.asdf = argparse.Namespace()

autofix causes:

Traceback (most recent call last):                                                                                                                                                                                                             
  File "foo.py", line 6, in <module>                                                
    asdfasfd.asdf = argparse.Namespace()       
    ^^^^^^^^                                               
NameError: name 'asdfasfd' is not defined   

Version

0.14.0

[ntBre]

cc @dylwil3

This is interesting, I would have assumed that the first import would still import asdfasfd even if a submodule import fails. Maybe that's not the case, or maybe something else is going wrong.

[dylwil3]

Interesting! If you look at the bytecode, Python only stores the symbol for the module if the full import succeeds:

>>> def func():
...       try:
...          import asdfasfd.asdf.sadf
...       except ImportError:
...          import argparse
...          import asdfasfd  # W: `asdfasfd` imported but unused
...          asdfasfd.asdf = argparse.Namespace()
...
>>> dis.dis(func)
   1           RESUME                   0

   2           NOP

   3   L1:     LOAD_SMALL_INT           0
               LOAD_CONST               1 (None)
               IMPORT_NAME              0 (asdfasfd.asdf.sadf)
               STORE_FAST               0 (asdfasfd)
       L2:     LOAD_CONST               1 (None)
               RETURN_VALUE

< rest omitted >

I'd have to think about how to detect situations like this... I guess more generally the presence of control flow would likely confuse the preview behavior.