pyqtProperty setter always raises an error #9911

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1. BoboTiG

   added

   bugmypy got something wrongmypy got something wrong

   on Jan 14, 2021
2. BoboTiG

   changed the title [-]pyqtProperty setter always raise an error[/-] [+]pyqtProperty setter always raises an error[/+] on Jan 14, 2021
3. freundTech commented on Jan 15, 2021

   

   freundTech

   on Jan 15, 2021

   Last edited by freundTech

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   On the Qt mailing-list someone already posted these two links to the mypy source-code:
   https://github.com/python/mypy/blob/v0.782/mypy/semanal.py#L964-L973
   https://github.com/python/mypy/blob/v0.782/mypy/semanal.py#L842-L869

   mypy has some special casing to make pythons @property (and a few other decorators) work.
   The easy solution would probably be to add a special case for @pyqtProperty.
   Cleaner solutions would be to either somehow make it possible to annotate that a decorator creates a property (This could be problematic, as I don't know if existing type annotations can handle this) or write a mypy plugin. I only took a quick look at the plugin interface and think it should be possible to do this. The problem here would be that the plugin API is unstable (See #6617).

   EDIT:
   Looks like writing a plugin for this isn't that easy after all. There is a "get_class_decorator_hook", but no corresponding hook for methods and functions. If such hooks would be added writing a plugin would be possible.
4. gvanrossum commented on Jan 15, 2021

   

   gvanrossum

   on Jan 15, 2021

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   The way to do that without baking knowledge of qt into mypy is to write a mypy extension.
5. freundTech commented on Jan 16, 2021

   

   freundTech

   on Jan 16, 2021

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   Should the plugin hook I suggested in #9915 get added to mypy you could solve this using the following mypy plugin (function and class names subject to change):

   from typing import Callable, Optional
   from typing import Type
   
   from mypy.plugin import (
       Plugin, DecoratorContext,
   )
   
   
   def plugin(version: str) -> Type[Plugin]:
       return PyQt5Plugin
   
   
   class PyQt5Plugin(Plugin):
       """PyQt5 Plugin"""
   
       def get_decorator_hook(self, fullname: str
                              ) -> Optional[Callable[[DecoratorContext], None]]:
           if fullname == 'PyQt5.QtCore.pyqtProperty':
               return pyqt_property_callback
           return None
   
   
   def pyqt_property_callback(ctx: DecoratorContext):
       ctx.decorator.func.is_property = True

   👍React with 👍3Reacted by Jonas, Mikhail Astafev and Edwin Yllanes
6. AlexWaygood

   added

   topic-descriptorsProperties, class vs. instance attributesProperties, class vs. instance attributes

   on Apr 4, 2022
7. djhoese

   added a commit that references this issue on May 9, 2023

   Resolve mypy issues in 'qml_utils.py'

   ...

   e825d3b