[stubtest] Support @final decorator on methods as well #14924

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1. sobolevn

   added

   feature

   on Mar 19, 2023
2. sobolevn

   self-assigned this

   on Mar 19, 2023
3. sobolevn

   added

   topic-stubtest

   on Mar 19, 2023
4. sobolevn commented on Mar 19, 2023

   

   sobolevn

   on Mar 19, 2023

   MemberAuthor

   More actions

   After working on for a short time, I've noticed several problems:

   1. @property is not supported
   2. @staticmethod is not supported
   3. @classmethod is not supported

   This happens, because __final__ cannot be set on property objects:

   See:

   >>> def my_final(f):
   ...    f.__final__ = True
   ...    return f

   >>> class P:
   ...    @my_final
   ...    @property
   ...    def p(self) -> int: ...
   ... 
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
     File "<stdin>", line 4, in P
     File "<stdin>", line 2, in my_final
   AttributeError: 'property' object has no attribute '__final__'

   But, @classmethod and @staticmethod actually change the object when using getattr, this is why this happens:

   >>> class St:
   ...   @my_final
   ...   @staticmethod
   ...   def m() -> None: ...
   ... 
   >>> St.m
   <function St.m at 0x109eeb400>
   >>> St.m.__final__
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
   AttributeError: 'function' object has no attribute '__final__'. Did you mean: '__init__'?
   
   >>> St.__dict__['m']
   <staticmethod(<function St.m at 0x109eeb400>)>
   >>> St.__dict__['m'].__final__
   True

   This needs:

   1. Special-casing properties. They cannot be supported right now
   2. Magic getattr_static to get methods from the class

   This is quite complicated for a Sunday's evening project, so - please feel free to continue it if someone finds it useful.
5. sobolevn

   removed their assignment

   on Mar 19, 2023
6. sobolevn

   added a commit that references this issue on Mar 24, 2023

   Stubtest: verify stub methods or properties are decorated with `@fina…

   ...

   01a088b
7. AlexWaygood commented on Mar 25, 2023

   

   AlexWaygood

   on Mar 25, 2023

   Member

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   To update on the status here: following #14951, this is now fully implemented except for cases where the method is overloaded in the stub (implementing that is blocked by #14950).
8. AlexWaygood

   added

   topic-finalPEP 591PEP 591

   on Mar 27, 2023