Incorporate typing_extensions into type checkers #19

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1. jakub-toptal

   added

   part:❓We need to figure out which part is affectedWe need to figure out which part is affected

   priority:❓We need to figure out how soon this should be addressedWe need to figure out how soon this should be addressed

   type:enhancementNew feature or enhancement visitble to usersNew feature or enhancement visitble to users

   on Oct 6, 2022
2. leandro-lucarella-frequenz commented on Oct 6, 2022

   

   leandro-lucarella-frequenz

   on Oct 6, 2022

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   One important clarification:

   Using Self is particularly useful for @classmethods acting as alternative constructors, because the cls argument should a special case in type checkers, as it is known that it always have to be the type of the class defining the @classmethod.

   But for @classmethods acting as alternative constructors, you also need to return the type of the class defining the @classmethod, and this has to work too for subclasses not re-defining the alternative constructor.

   As a workaround we can use the class name explicitly.

   For example:

   class S:
       @classmethod
       def make(cls) -> S:
           return cls()
   
   class T(S):
       pass
   
   def print_t(t: T) -> None:
       print(t)
   
   print_t(T.make())

   This should fail a type checking, because T.make() is marked to return a S, not a T. But this should work:

   from typing_extensions import Self
   
   class S:
       @classmethod
       def make(cls) -> Self:  # <------
           return cls()
   
   class T(S):
       pass
   
   def print_t(t: T) -> None:
       print(t)
   
   print_t(T.make())

   Note: this is untested because mypy doesn't support Self yet, but is what I assume it should happen :)
3. leandro-lucarella-frequenz commented on Oct 7, 2022

   

   leandro-lucarella-frequenz

   on Oct 7, 2022

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   Some other important clarifications:

   • Self is introduced in Python 3.11.
   • typing-extensions is not a random package, is an official Python package maintained by the Python organization and only includes features backported from newer Python versions so they are available for older versions. Thus the use of this package is by definition temporary (until we can depend on a new enough Python minimal version)
   • mypy doesn't support Self yet, this is why we didn't go for it. There is a PR, so support should come fairly soon. Implementation of PEP 673 (typing.Self) python/mypy#11666
   • This comes from another PR's discussion: Change component data wrappers to be data classes #4 (comment)
4. jakub-toptal

   removed

   part:❓We need to figure out which part is affectedWe need to figure out which part is affected

   priority:❓We need to figure out how soon this should be addressedWe need to figure out how soon this should be addressed

   on Oct 7, 2022
5. leandro-lucarella-frequenz commented on Apr 21, 2023

   

   leandro-lucarella-frequenz

   on Apr 21, 2023

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   We already have typing_extensions as a dependency and mypy already supports Self, we just need to start using it.
6. leandro-lucarella-frequenz

   closed this as completedon Apr 21, 2023
7. leandro-lucarella-frequenz

   added this to the v0.20.0 milestone on Apr 21, 2023
8. leandro-lucarella-frequenz

   added this to Python SDK Roadmapon Apr 21, 2023
9. github-project-automation

   moved this to To do in Python SDK Roadmapon Apr 21, 2023
10. leandro-lucarella-frequenz

    self-assigned this

    on Apr 21, 2023
11. sahas-subramanian-frequenz

    moved this from To do to Done in Python SDK Roadmapon Apr 26, 2023