Fixed TypedAttributeSet rejecting its own subclasses

[pasmud]

Changes

Fixes #.

TypedAttributeSet.__init_subclass__() compared every public name in dir(cls) against
cls.__annotations__. Since Python 3.10, __annotations__ only ever contains the
annotations declared in the class itself, never the inherited ones, so every attribute
inherited from a base class was reported as missing its type annotation:

>>> class MyTypedAttribute(TypedAttributeSet):
...     string_valued_attribute: str = typed_attribute()
>>> class MyOtherTypedAttribute(MyTypedAttribute):
...     some_float_attribute: float = typed_attribute()
TypeError: Attribute 'string_valued_attribute' is missing its type annotation

That made subclassing a typed attribute set impossible, even though the class docstring
says the check applies to "every public attribute of every subclass", and extending the
documented providers and attribute sets is the natural way to use the typed attribute
system. It only went unnoticed because all three built-in sets (SocketAttribute,
FileStreamAttribute, TLSAttribute) declare every public attribute directly.

The check now gathers the annotations across the whole MRO. The attributes a class
declares itself are still required to be annotated, and the built-in sets are unaffected.

The annotations are collected without being evaluated, so unlike get_type_hints() this
does not require the annotation names to be resolvable at class creation time, which
would otherwise turn an unresolvable forward reference into a NameError.

Checklist

• You've added tests (in tests/) which would fail without your patch
• You've updated the documentation (in docs/), in case of behavior changes or new
  features
• You've added a new changelog entry (in docs/versionhistory.rst).

[pasmud]

A note on the current CI status, since most of it is unrelated to this patch.

The first run failed the docs job because the pull request link in my changelog
entry was written with a double backtick instead of the single backtick the RST link
syntax needs. That has been fixed in c280702, and the docs job now passes.

The remaining red marks on the latest run are not caused by this patch:

• 13 of the 14 failing jobs failed only in the Upload Coverage step with
  Error: Internal Server Error (500) from Coveralls. The Test with pytest step
  succeeded in every one of them.
• The one job whose Test with pytest step failed is
  test (ubuntu-latest, pypy3.11-v7.3.23, [trio], false), on
  test_sockets.py::TestTCPStream::test_cancelled_send_does_not_send_the_next_one[trio-ipv6].
  That test sends an 8 MB payload and depends on wait_all_tasks_blocked() timing. It
  passes here on all 6 of its parametrizations, and the same job has flaked on master
  before. All five tests in tests/test_typedattr.py passed in that job.

[agronholm]

It looks like this PR comes with too many tests, not all of them focusing on this particular fix. Keep only the relevant tests (1 might be enough).

[agronholm]

Only test_typedattr_set_subclassing actually exercises the fix. The other tests either cover pre-existing behavior or go through the same code path, and the asserts in the remaining test can never fail (creating the class without a TypeError is the test). Suggest trimming down to this:

Suggested change

	def test_typedattr_set_missing_annotation() -> None:
	"""
	Test that a public attribute without a type annotation is rejected.
	"""
	with pytest.raises(
	TypeError, match="^Attribute 'attr' is missing its type annotation$"
	):
	class BadAttributeSet(TypedAttributeSet):
	attr = typed_attribute()
	def test_typedattr_set_subclassing() -> None:
	"""
	Test that an attribute set can be subclassed, and that the attributes inherited
	from the base set are not reported as missing annotations.
	"""
	class BaseAttributeSet(TypedAttributeSet):
	attr1: int = typed_attribute()
	class DerivedAttributeSet(BaseAttributeSet):
	attr2: str = typed_attribute()
	assert DerivedAttributeSet.attr1 is BaseAttributeSet.attr1
	assert DerivedAttributeSet.attr2 is not None
	assert "attr2" in dir(DerivedAttributeSet)
	def test_typedattr_set_empty_subclass() -> None:
	"""
	Test that a subclass that adds no attributes of its own is accepted.
	"""
	class BaseAttributeSet(TypedAttributeSet):
	attr1: int = typed_attribute()
	class DerivedAttributeSet(BaseAttributeSet):
	pass
	assert DerivedAttributeSet.attr1 is BaseAttributeSet.attr1
	def test_typedattr_set_subclass_missing_annotation() -> None:
	"""
	Test that the annotation check still applies to the attributes declared by the
	subclass itself.
	"""
	class BaseAttributeSet(TypedAttributeSet):
	attr1: int = typed_attribute()
	with pytest.raises(
	TypeError, match="^Attribute 'attr2' is missing its type annotation$"
	):
	class DerivedAttributeSet(BaseAttributeSet):
	attr2 = typed_attribute()
	def test_typedattr_set_subclassing() -> None:
	"""
	Test that an attribute set can be subclassed, and that the attributes inherited
	from the base set are not reported as missing annotations.
	"""
	class BaseAttributeSet(TypedAttributeSet):
	attr1: int = typed_attribute()
	class DerivedAttributeSet(BaseAttributeSet):
	attr2: str = typed_attribute()