bpo-46571: improve typing.no_type_check to skip foreign objects

[sobolevn]

There are several changes:

1. We now don't explicitly check for any base / sub types, because new name check covers it
2. I've also checked that no_type_check do not modify foreign functions. It was the same as with types
3. I've also covered except TypeError in no_type_check with a simple test case, it was not covered at all
4. I also felt like adding lambda test is a good idea: because lambda is a bit of both in class bodies: a function and an assignment

Are there any other cases we want to cover?

https://bugs.python.org/issue46571

[AlexWaygood]

Here's a slightly evil corner case that this patch doesn't account for:

If I have a module typing_test.py, like so:

# typing_test.pyclassA:
classAA:
foo: int

Then, observe the following behaviour (with your patch applied):

>>>fromtypingimportget_type_hints, no_type_check>>>importtyping_test>>>get_type_hints(typing_test.A.AA)
{'foo':<class'int'>}
>>> @no_type_check
... classA:
... AA=typing_test.A.AA
... ... >>>get_type_hints(typing_test.A.AA)
{}

We might be able to get around this by looking at the __module__ attribute.

[sobolevn]

@AlexWaygood good one! Very evil!

I've addressed this.

@JelleZijlstra I agree that we should also fix classmethod / staticmethod problem. Because we declare to support all methods, not just instance methods.

The problem is that types.MethodType does not support attribute assignment:

>>>classSome:
... @staticmethod
... defst(x: int) ->int: ...
... @classmethod
... defcl(cls, y: int) ->int: ...
>>>Some.st.__no_type_check__=True>>>Some.cl.__no_type_check__=TrueAttributeError: 'method'objecthasnoattribute'__no_type_check__'

Ideas?

Moreover, do we need some special @property support?

[AlexWaygood]

@AlexWaygood good one! Very evil!

I've addressed this.

Doesn't look like you've pushed anything -- did you mean to? :)

[sobolevn]

Doesn't look like you've pushed anything -- did you mean to? :)

Not yet, I am still fighting classmethod 🙂

[sobolevn]

Probably

ifisinstance(obj, types.MethodType):
obj.__func__.__no_type_check__=True

is the way to go 🤔

Will write some more tests to be sure.

[JelleZijlstra]

Looks good.

Do you think this should be backported? I'm leaning no as it's a behavior change and nobody directly complained about the old behavior (looks like you found it while reviewing typing test coverage).

[gvanrossum]

Agreed, a backport doesn't seem asked for.