(Python): @jsii.python.classproperty not working as intended with type checking

[gshpychka]

Describe the bug

Static properties in the generated Python code are not correctly interpreted by the type checking system. They're recognized as class methods, and require casting.

Consider the following example snippet:

ec2.Vpc(self, "vpc", sugnet_configuration=ec2.Vpc.DEFAULT_SUBNETS)

Expected Behavior

pyright does not report any issues

Current Behavior

Type checker interprets the type of the property as a callable method

error: Argument of type "(cls: Vpc) -> List[SubnetConfiguration]" cannot be assigned to parameter "subnet_configuration" of type "Sequence[SubnetConfiguration] | None" in function "__init__"
    Type "(cls: Vpc) -> List[SubnetConfiguration]" cannot be assigned to type "Sequence[SubnetConfiguration] | None"
      "object" is incompatible with "Sequence[SubnetConfiguration]"
      Type cannot be assigned to type "None"

Reproduction Steps

Use any static property and enable type checking.

Possible Solution

No response

Additional Information/Context

No response

SDK version used

1.61.0

Environment details (OS name and version, etc.)

Linux

[RomainMuller]

Okay this is weird as I have definitely been validating that and it did not cause any issues with my setup, where it was considered all good (we actually run mypy on our test code, which includes references to static properties, too).

Would you be able to try and replace the jsii/python.py file in your install with the one in #3694, and tell me whether that fixes your type checking issue?

[gshpychka]

@RomainMuller assuming I did this right (replaced the file in my .venv/lib/python3.10/site-packages/jsii with the one from the PR and didn't do anything else), then no, it didn't change anything.

[RomainMuller]

This feels like the type checker you're using might be incorrectly handling property descriptors... can you tell more about what the setup/tooling is?

[gshpychka]

This is Pyright with default settings. Pyright version is 1.1.264 if that helps.

[RomainMuller]

Okay... I've tried running PyRight on the jsii runtime for Python... it definitely found some issues that mypy did not... I'm going to try to dig deeper... it appears to be pretty strict (and I mean that as a compliment) and our property descriptor might not satisfy it entirely...

[RomainMuller]

I found the cause of the issue to be that the jsii/__init__.py does not correctly re-export jsii.python, and so the type-checker ends up assuming it's an Any...

[gshpychka]

It'd be awesome if pyright were included in the test suite. It's the type checker used in Pylance, VS Code's Python language server.

[RomainMuller]

@gshpychka yep... I'm actually adding pyright in addition to mypy... Maybe eventually I'll get rid of mypy (but I know some users are using it and I'd rather they not be surprised).

[RomainMuller]

I think I might have hit a bug in pyright 🙃 (microsoft/pyright#3781)

[github-actions]

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[iliapolo]

Reopening as I can confirm this still doesn't work as expected with PyCharm:

Note I had to change code insights max file size to see these warnings.

PyCharm thinks that ec2.Vpc.DEFAULT_SUBNETS is a classmethod. Indeed, if I change the code to:

It stops complaining. VSCode though doesn't seem to exhibit this issue: