"maximum recursion depth exceeded while calling a Python object" while calling long chain of methods

[gladykov]

When multiple methods are chained on the object together (~140), Bugbear will cause maximum recursion depth exceeded while calling a Python object

Steps to reproduce:

0. Windows, Python 3.8, Bugbear 22.9.23
1. Download and rename chain_method.txt to chain_method.py

pip install flake8 flake8-bugbear
flake8 .

Result:

Traceback (most recent call last):
  File "c:\program files\python38\lib\runpy.py", line 194, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "c:\program files\python38\lib\runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "C:\Program Files\Python38\Scripts\flake8.exe\__main__.py", line 7, in <module>
  File "c:\program files\python38\lib\site-packages\flake8\main\cli.py", line 22, in main
    app.run(argv)
  File "c:\program files\python38\lib\site-packages\flake8\main\application.py", line 375, in run
    self._run(argv)
  File "c:\program files\python38\lib\site-packages\flake8\main\application.py", line 364, in _run
    self.run_checks()
  File "c:\program files\python38\lib\site-packages\flake8\main\application.py", line 271, in run_checks
    self.file_checker_manager.run()
  File "c:\program files\python38\lib\site-packages\flake8\checker.py", line 311, in run
    self.run_serial()
  File "c:\program files\python38\lib\site-packages\flake8\checker.py", line 295, in run_serial
    checker.run_checks()
  File "c:\program files\python38\lib\site-packages\flake8\checker.py", line 597, in run_checks
    self.run_ast_checks()
  File "c:\program files\python38\lib\site-packages\flake8\checker.py", line 500, in run_ast_checks
    for (line_number, offset, text, _) in runner:
  File "c:\program files\python38\lib\site-packages\bugbear.py", line 60, in run
    visitor.visit(self.tree)
  File "c:\program files\python38\lib\site-packages\bugbear.py", line 268, in visit
    super().visit(node)
  File "c:\program files\python38\lib\ast.py", line 371, in visit
    return visitor(node)
  File "c:\program files\python38\lib\ast.py", line 379, in generic_visit
    self.visit(item)
  File "c:\program files\python38\lib\site-packages\bugbear.py", line 268, in visit
    super().visit(node)
  File "c:\program files\python38\lib\ast.py", line 371, in visit
    return visitor(node)
  File "c:\program files\python38\lib\ast.py", line 381, in generic_visit
    self.visit(value)
  File "c:\program files\python38\lib\site-packages\bugbear.py", line 268, in visit
    super().visit(node)
  File "c:\program files\python38\lib\ast.py", line 371, in visit
    return visitor(node)
  File "c:\program files\python38\lib\site-packages\bugbear.py", line 357, in visit_Call
    self.generic_visit(node)
  File "c:\program files\python38\lib\ast.py", line 381, in generic_visit
    self.visit(value)
  File "c:\program files\python38\lib\site-packages\bugbear.py", line 268, in visit

This continues until error is reached:

RecursionError: maximum recursion depth exceeded while calling a Python object

Use case: We use such long chains to describe internal schema of DB

[cooperlees]

So what do you actually want here to fix it? I guess we could add a config parameter to set sys.setrecursionlimit: https://docs.python.org/3/library/sys.html#sys.setrecursionlimit

You could then set this for your deep recursive code ...

[gladykov]

Thank you, I was not aware of this setting. Not sure then if bugbear would be the best place. Maybe flake8 repo would be a place to ask for command line parameter, to increase it - would be more efficient , as in theory would apply to any plugin (?)

[cooperlees]

Agree. I only suggested config as we (bugbear plug-in) have no way to change the CLI but I think we can get at the config easier (I’ve never tried).

Yes, this could occur on any plug-in depending how it works. We are AST based so your large files cause a lot of recursion with our parsing. You could also, be hilighting a bug, but I don’t think so due to you claiming very large files.

It’s definitely a better solution to ask flake8 itself here how they want to handle it.

[gladykov]

Thank you. Well maybe someone will also encounter this in the future. For now we divided those long blocks of chained methods. Closing then.