AssertionError: Unexpected node type: <class 'ast.Subscript'> on version > 23.2.13

[ecs-jnguyen]

Hi when I use flake8, I'm getting this exception AssertionError: Unexpected node type: <class 'ast.Subscript'>. I notice the error on version 23.2.13 and 23.3.12. When I revert back to 23.1.20 the error goes away.

Stack Trace

Expand

multiprocessing.pool.RemoteTraceback: 
"""
Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/multiprocessing/pool.py", line 125, in worker
    result = (True, func(*args, **kwds))
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/multiprocessing/pool.py", line 48, in mapstar
    return list(map(*args))
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/flake8/checker.py", line 621, in _run_checks
    return checker.run_checks()
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/flake8/checker.py", line 531, in run_checks
    self.run_ast_checks()
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/flake8/checker.py", line 435, in run_ast_checks
    for (line_number, offset, text, _) in runner:
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/bugbear.py", line 61, in run
    visitor.visit(self.tree)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/bugbear.py", line 336, in visit
    super().visit(node)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/ast.py", line 407, in visit
    return visitor(node)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/bugbear.py", line 417, in visit_Module
    self.generic_visit(node)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/ast.py", line 415, in generic_visit
    self.visit(item)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/bugbear.py", line 336, in visit
    super().visit(node)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/ast.py", line 407, in visit
    return visitor(node)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/bugbear.py", line 482, in visit_ClassDef
    self.generic_visit(node)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/ast.py", line 415, in generic_visit
    self.visit(item)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/bugbear.py", line 336, in visit
    super().visit(node)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/ast.py", line 407, in visit
    return visitor(node)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/bugbear.py", line 475, in visit_FunctionDef
    self.generic_visit(node)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/ast.py", line 415, in generic_visit
    self.visit(item)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/bugbear.py", line 336, in visit
    super().visit(node)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/ast.py", line 407, in visit
    return visitor(node)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/bugbear.py", line 487, in visit_Try
    self.generic_visit(node)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/ast.py", line 415, in generic_visit
    self.visit(item)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/bugbear.py", line 336, in visit
    super().visit(node)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/ast.py", line 407, in visit
    return visitor(node)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/bugbear.py", line 360, in visit_ExceptHandler
    names = [_to_name_str(e) for e in good_handlers]
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/bugbear.py", line 360, in <listcomp>
    names = [_to_name_str(e) for e in good_handlers]
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/bugbear.py", line 259, in _to_name_str
    return _to_name_str(node.value) + "." + node.attr
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/bugbear.py", line 259, in _to_name_str
    return _to_name_str(node.value) + "." + node.attr
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/bugbear.py", line 257, in _to_name_str
    assert isinstance(node, ast.Attribute), f"Unexpected node type: {type(node)}"
AssertionError: Unexpected node type: <class 'ast.Subscript'>
"""

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/opt/hostedtoolcache/Python/3.9.16/x64/bin/flake8", line 8, in <module>
    sys.exit(main())
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/flake8/main/cli.py", line 22, in main
    app.run(argv)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/flake8/main/application.py", line 336, in run
    self._run(argv)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/flake8/main/application.py", line 325, in _run
    self.run_checks()
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/flake8/main/application.py", line 229, in run_checks
    self.file_checker_manager.run()
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/flake8/checker.py", line 250, in run
    self.run_parallel()
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/site-packages/flake8/checker.py", line 217, in run_parallel
    for ret in pool_map:
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/multiprocessing/pool.py", line 448, in <genexpr>
    return (item for chunk in result for item in chunk)
  File "/opt/hostedtoolcache/Python/3.9.16/x64/lib/python3.9/multiprocessing/pool.py", line 870, in next
    raise value
AssertionError: Unexpected node type: <class 'ast.Subscript'>

[FozzieHi]

Thanks for the report. Does this happen when you run flake8 against a specific file, or is it a more general issue?

[JelleZijlstra]

Seems to be related to except handlers, I'll take a look. Possibly happens on something like except a[0].b:.

[ecs-jnguyen]

I'm running it on an entire repository

[ecs-jnguyen]

I found the issue file. I believe you are right @FozzieHi, I see there's a block that looks like this. When I updated that line the error went away:

something = ...
try:
    ...
except something["abc"].exception.Exception:
    ...