Protocol named "Protocol" or "Generic" has no members.

[danielknell]

Bug report

Bug description:

If a protocol is named Protocol or Generic then it will ignore any defined members.

when you get lazy with naming in your unit tests this makes for quite a head scratcher...

Minimal Reproduction

import typing


class Protocol(typing.Protocol):
    a: int


members = typing.get_protocol_members(Protocol)

assert members == {"a"}, f"Expected members to be {{'a'}}, got {members}"

Output:

Traceback (most recent call last):
  File ".../test_protocol.py", line 10, in <module>
    assert members == {"a"}, f"Expected members to be {{'a'}}, got {members}"
           ^^^^^^^^^^^^^^^^
AssertionError: Expected members to be {'a'}, got frozenset()

Expected Output:

Nothing, script should succeed without error.

Investigation

The problem appears to stem from the _get_protocol_attrs function used by _ProtocolMeta which is defined as follows:

cpython/Lib/typing.py

Lines 1879 to 1899 in 171133a

	def _get_protocol_attrs(cls):
	"""Collect protocol members from a protocol class objects.
	This includes names actually defined in the class dictionary, as well
	as names that appear in annotations. Special names (above) are skipped.
	"""
	attrs = set()
	for base in cls.__mro__[:-1]: # without object
	if base.__name__ in {'Protocol', 'Generic'}:
	continue
	try:
	annotations = base.__annotations__
	except Exception:
	# Only go through annotationlib to handle deferred annotations if we need to
	annotations = _lazy_annotationlib.get_annotations(
	base, format=_lazy_annotationlib.Format.FORWARDREF
	)
	for attr in (*base.__dict__, *annotations):
	if not attr.startswith('_abc_') and attr not in EXCLUDED_ATTRIBUTES:
	attrs.add(attr)
	return attrs

The if statement on line 1887 is too loose in what it matches.

Possibile Fix

The check for base needs to be more specific, either using the instance itself:

if base in {Protocol, Generic}:
    continue

or checking the module too, in order to ensure its the correct class being excluded:

if base.__name__ in {'Protocol', 'Generic'} and base.__module__ == 'typing':
    continue

CPython versions tested on:

3.14

Operating systems tested on:

macOS

Linked PRs

• gh-145688: Fix _get_protocol_attrs matching user classes named "Protocol" or "Generic" #145724

[mvanhorn]

I've submitted a fix for this in PR #145724. Changed the name-based check to also verify base.__module__ == 'typing' so user-defined Protocol subclasses named "Protocol" or "Generic" are no longer skipped.