[Backport maintenance/2.15.x] Define Protocol as abstract to prevent abstract-method FP

doc/whatsnew/fragments/7209.false_positive

@@ -0,0 +1,3 @@
+Fixes false positive ``abstract-method`` on Protocol classes.
+
+Closes #7209

pylint/checkers/classes/class_checker.py

@@ -2085,19 +2085,9 @@ def _check_init(self, node: nodes.FunctionDef, klass_node: nodes.ClassDef) -> No
             if node_frame_class(method) in parents_with_called_inits:
                 return
 
-            # Return if klass is protocol
-            if klass.qname() in utils.TYPING_PROTOCOLS:
+            if utils.is_protocol_class(klass):
                 return
 
-            # Return if any of the klass' first-order bases is protocol
-            for base in klass.bases:
-                try:
-                    for inf_base in base.infer():
-                        if inf_base.qname() in utils.TYPING_PROTOCOLS:
-                            return
-                except astroid.InferenceError:
-                    continue
-
             if decorated_with(node, ["typing.overload"]):
                 continue
             self.add_message(

pylint/checkers/utils.py

@@ -1151,6 +1151,10 @@ def class_is_abstract(node: nodes.ClassDef) -> bool:
     """Return true if the given class node should be considered as an abstract
     class.
     """
+    # Protocol classes are considered "abstract"
+    if is_protocol_class(node):
+        return True
+
     # Only check for explicit metaclass=ABCMeta on this specific class
     meta = node.declared_metaclass()
     if meta is not None:
@@ -1595,14 +1599,23 @@ def is_protocol_class(cls: nodes.NodeNG) -> bool:
     """Check if the given node represents a protocol class.
 
     :param cls: The node to check
-    :returns: True if the node is a typing protocol class, false otherwise.
+    :returns: True if the node is or inherits from typing.Protocol directly, false otherwise.
     """
     if not isinstance(cls, nodes.ClassDef):
         return False
 
-    # Use .ancestors() since not all protocol classes can have
-    # their mro deduced.
-    return any(parent.qname() in TYPING_PROTOCOLS for parent in cls.ancestors())
+    # Return if klass is protocol
+    if cls.qname() in TYPING_PROTOCOLS:
+        return True
+
+    for base in cls.bases:
+        try:
+            for inf_base in base.infer():
+                if inf_base.qname() in TYPING_PROTOCOLS:
+                    return True
+        except astroid.InferenceError:
+            continue
+    return False
 
 
 def is_call_of_name(node: nodes.NodeNG, name: str) -> bool:

tests/functional/p/protocol_classes_abstract.py

@@ -0,0 +1,46 @@
+"""Test that classes inheriting directly from Protocol should not warn about abstract-method."""
+
+# pylint: disable=too-few-public-methods,disallowed-name,invalid-name
+
+from abc import abstractmethod, ABCMeta
+from typing import Protocol, Literal
+
+
+class FooProtocol(Protocol):
+    """Foo Protocol"""
+
+    @abstractmethod
+    def foo(self) -> Literal["foo"]:
+        """foo method"""
+
+    def foo_no_abstract(self) -> Literal["foo"]:
+        """foo not abstract method"""
+
+
+class BarProtocol(Protocol):
+    """Bar Protocol"""
+    @abstractmethod
+    def bar(self) -> Literal["bar"]:
+        """bar method"""
+
+
+class FooBarProtocol(FooProtocol, BarProtocol, Protocol):
+    """FooBar Protocol"""
+
+class BarParent(BarProtocol): # [abstract-method]
+    """Doesn't subclass typing.Protocol directly"""
+
+class IndirectProtocol(FooProtocol):  # [abstract-method]
+    """Doesn't subclass typing.Protocol directly"""
+
+class AbcProtocol(FooProtocol, metaclass=ABCMeta):
+    """Doesn't subclass typing.Protocol but uses metaclass directly"""
+
+class FooBar(FooBarProtocol):
+    """FooBar object"""
+
+    def bar(self) -> Literal["bar"]:
+        return "bar"
+
+    def foo(self) -> Literal["foo"]:
+        return "foo"

tests/functional/p/protocol_classes_abstract.rc

@@ -0,0 +1,2 @@
+[testoptions]
+min_pyver=3.8

tests/functional/p/protocol_classes_abstract.txt

@@ -0,0 +1,2 @@
+abstract-method:30:0:30:15:BarParent:Method 'bar' is abstract in class 'BarProtocol' but is not overridden:UNDEFINED
+abstract-method:33:0:33:22:IndirectProtocol:Method 'foo' is abstract in class 'FooProtocol' but is not overridden:UNDEFINED