Link to issue number:

Fixes #13923

Summary of the issue:

Performing type checks for collections fail

The following code raises an error when FlagValueEnum is defined as

FlagValueEnum(enum.EnumMeta, _DisplayStringEnumMixin, FeatureFlagEnumProtocol): pass

In the NVDA python console

>>>import collections.abc
>>>isinstance(12, collections.abc.Sized)
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "C:\Users\sean\AppData\Local\Programs\Python\Python37-32\lib\abc.py", line 139, in __instancecheck__
    return _abc_instancecheck(cls, instance)
  File "C:\Users\sean\AppData\Local\Programs\Python\Python37-32\lib\abc.py", line 143, in __subclasscheck__
    return _abc_subclasscheck(cls, subclass)
  File "C:\Users\sean\AppData\Local\Programs\Python\Python37-32\lib\abc.py", line 143, in __subclasscheck__
    return _abc_subclasscheck(cls, subclass)
  File "C:\Users\sean\AppData\Local\Programs\Python\Python37-32\lib\abc.py", line 143, in __subclasscheck__
    return _abc_subclasscheck(cls, subclass)
  [Previous line repeated 1 more time]
TypeError: descriptor '__subclasses__' of 'type' object needs an argument

Description of user facing changes

API is fixed for performing type checks in collections.

Description of development approach

Removing typing.Collection or enum.EnumMeta from the MRO both resolve the python console / API bug.
As a result, I assume the bug is some sort of class conflict between typing.Collection and enum.EnumMeta .
We could resolve this by creating a metaclass.
However, I believe the already included EnumMeta class should cover what we wanted in type hinting typing.Collection.

The EnumMeta metaclass is responsible for providing the __contains__(), __dir__(), __iter__() and other methods that allow one to do things with an Enum class that fail on a typical class, such as list(Color) or some_enum_var in Color. EnumMeta is responsible for ensuring that various other methods on the final Enum class are correct (such as __new__(), __getnewargs__(), __str__() and __repr__()).

https://docs.python.org/3/library/enum.html#enum-classes.

Testing strategy:

Tested with add-on and python console.

Known issues with pull request:

None

Change log entries:

Unreleased regressions

Code Review Checklist:

• Pull Request description:
  • description is up to date
  • change log entries
• Testing:
  • Unit tests
  • System (end to end) tests
  • Manual testing
• API is compatible with existing add-ons.
• Documentation:
  • User Documentation
  • Developer / Technical Documentation
  • Context sensitive help for GUI changes
• UX of all users considered:
  • Speech
  • Braille
  • Low Vision
  • Different web browsers
  • Localization in other languages / culture than English