Generic class using ParamSpec raises TypeError in Python < 3.10, with User Uncaught Exceptions + justMyCode: false

[ringohoffman]

Environment data

• debugpy version: 1.6.7
• OS and version: M1 Pro, macOS 13.5 (22G74)
• Python version (& distribution if applicable, e.g. Anaconda): conda for M1/M2, Python 3.8.17
• Using VS Code or Visual Studio: VS Code Version: 1.80.2 Commit: 2ccd690cbff1569e4a83d7c43d45101f817401dc

I didn't have this problem until today when I switched to conda for M1/M2 (from the Intel based one).

from typing import Generic

from typing_extensions import ParamSpec

P = ParamSpec("P")


class A(Generic[P]):
    ...

The above code executes fine:

$ python --version
Python 3.8.17
$ python a.py

Actual behavior

But when when both:

1. justMyCode: false
2. Breakpoints > User Uncaught Exceptions is checked

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Python: Current File",
            "type": "python",
            "request": "launch",
            "program": "${file}",
            "console": "integratedTerminal",
            "subProcess": true,
            "justMyCode": false
        },
    ]
}

I get this stack trace:

Exception has occurred: TypeError       (note: full exception trace is shown but execution is paused at: <module>)
Parameters to Generic[...] must all be type variables
  File "/Users/ringo/anaconda3/envs/glass38/lib/python3.8/typing.py", line 890, in __class_getitem__
    raise TypeError(
  File "/Users/ringo/anaconda3/envs/glass38/lib/python3.8/typing.py", line 261, in inner
    return func(*args, **kwds)
  File "/Users/ringo/Repositories/stained-glass-factory/a.py", line 9, in <module> (Current frame)
    class A(Generic[P]):
  File "/Users/ringo/anaconda3/envs/glass38/lib/python3.8/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "/Users/ringo/anaconda3/envs/glass38/lib/python3.8/runpy.py", line 194, in _run_module_as_main
    return _run_code(code, main_globals, None,
TypeError: Parameters to Generic[...] must all be type variables

This occurs because in the typing_extensions.ParamSpec for Python<3.10 :

class ParamSpec(list, _DefaultMixin):
    ...
    __class__ = typing.TypeVar

But when I set a breakpoint immediately after this definition and check ParamSpec("P").__class__, I see <class 'typing_extensions.ParamSpec'>. If I copy and paste the source code for ParamSpec in the debug console and try it again, it actually works as expected...

Expected behavior

I don't expect there to be an error in this class definition when debugging.

Steps to reproduce:

1. Use conda for M1 and create an environment with python < 3.10
2. activate and pip install typing_extensions
3. Use VS Code for Apple Silicon
4. Run the debugger with justMyCode: false and check User Uncaught Exceptions
5. Debug the above code

[qthequartermasterman]

I am having the same issue on python==3.9 on M1 Mac.

Version: 1.80.2
Commit: 2ccd690cbff1569e4a83d7c43d45101f817401dc

[agustingomes-therapieland]

I am experiencing similar issues on a project I'm working, also on a M1 Mac, but in my case, it manifests when I use the PyCharm debugger with any Django's ./manage.py command.

I am fairly new to the Python ecosystem, so if you need more details about the environment, I'll be happy to provide them.

EDIT:

I used the same code snippet that @ringohoffman provided, and I have the same outcome, which then gives me the feeling this particular issue might not be solely related to this project.