pythongh-104873: Add typing.get_protocol_members

Doc/library/typing.rst

@@ -2905,6 +2905,23 @@ Introspection helpers
 
    .. versionadded:: 3.8
 
+.. function:: get_protocol_members(tp)
+
+   Return the set of members defined in a :class:`Protocol`.
+
+   ::
+
+      >>> from typing import Protocol, get_protocol_members
+      >>> class P(Protocol):
+      ...     def a(self) -> str: ...
+      ...     b: int
+      >>> get_protocol_members(P)
+      {'a', 'b'}
+
+   Return None for arguments that are not Protocols.
+
+   .. versionadded:: 3.13
+
 .. function:: is_typeddict(tp)
 
    Check if a type is a :class:`TypedDict`.

Doc/whatsnew/3.13.rst

@@ -87,6 +87,13 @@ New Modules
 Improved Modules
 ================
 
+typing
+------
+
+* Added :func:`typing.get_protocol_members` to return the set of members
+  defining a :class:`typing.Protocol`. (Contributed by Jelle Zijlstra in
+  :gh:`104873`.)
+
 
 Optimizations
 =============

Lib/test/test_typing.py

@@ -22,7 +22,7 @@
 from typing import Generic, ClassVar, Final, final, Protocol
 from typing import assert_type, cast, runtime_checkable
 from typing import get_type_hints
-from typing import get_origin, get_args
+from typing import get_origin, get_args, get_protocol_members
 from typing import override
 from typing import is_typeddict
 from typing import reveal_type
@@ -3172,6 +3172,11 @@ def meth(self): pass
         self.assertNotIn("__callable_proto_members_only__", vars(NonP))
         self.assertNotIn("__callable_proto_members_only__", vars(NonPR))
 
+        self.assertIs(get_protocol_members(NonP), None)
+        self.assertIs(get_protocol_members(NonPR), None)
+        self.assertEqual(get_protocol_members(P), {"x"})
+        self.assertEqual(get_protocol_members(PR), {"meth"})
+
         acceptable_extra_attrs = {
             '_is_protocol', '_is_runtime_protocol', '__parameters__',
             '__init__', '__annotations__', '__subclasshook__',
@@ -3587,6 +3592,39 @@ def __init__(self):
 
         Foo()  # Previously triggered RecursionError
 
+    def test_get_protocol_members(self):
+        self.assertIs(get_protocol_members(object), None)
+        self.assertIs(get_protocol_members(object()), None)
+        self.assertIs(get_protocol_members(Protocol), None)
+        self.assertIs(get_protocol_members(Generic), None)
+
+        class P(Protocol):
+            a: int
+            def b(self) -> str: ...
+            @property
+            def c(self) -> int: ...
+
+        self.assertEqual(get_protocol_members(P), {'a', 'b', 'c'})
+
+        class Concrete:
+            a: int
+            def b(self) -> str: return "capybara"
+            @property
+            def c(self) -> int: return 5
+
+        self.assertIs(get_protocol_members(Concrete), None)
+        self.assertIs(get_protocol_members(Concrete()), None)
+
+        class ConcreteInherit(P):
+            a: int = 42
+            def b(self) -> str: return "capybara"
+            @property
+            def c(self) -> int: return 5
+
+        # not a protocol
+        self.assertEqual(get_protocol_members(ConcreteInherit), None)
+        self.assertIs(get_protocol_members(ConcreteInherit()), None)
+
 
 class GenericTests(BaseTestCase):
 

Lib/typing.py

@@ -132,6 +132,7 @@
     'get_args',
     'get_origin',
     'get_overloads',
+    'get_protocol_members',
     'get_type_hints',
     'is_typeddict',
     'LiteralString',
@@ -3296,3 +3297,23 @@ def method(self) -> None:
         # read-only property, TypeError if it's a builtin class.
         pass
     return method
+
+
+def get_protocol_members(tp: type, /) -> set[str]:
+    """Return the set of members defined in a Protocol.
+
+    Example::
+
+        >>> from typing import Protocol, get_protocol_members
+        >>> class P(Protocol):
+        ...     def a(self) -> str: ...
+        ...     b: int
+        >>> get_protocol_members(P)
+        {'a', 'b'}
+
+    Return None for arguments that are not Protocols.
+
+    """
+    if not getattr(tp, '_is_protocol', False) or tp is Protocol:
+        return None
+    return tp.__protocol_attrs__

Misc/NEWS.d/next/Library/2023-05-24-09-55-33.gh-issue-104873.BKQ54y.rst

@@ -0,0 +1,2 @@
+Add :func:`typing.get_protocol_members` to return the set of members
+defining a :class:`typing.Protocol`. Patch by Jelle Zijlstra.