Warn on incomplete concrete classes that inherit from abstract classes

pylint/checkers/utils.py

@@ -1164,9 +1164,14 @@ def class_is_abstract(node: nodes.ClassDef) -> bool:
         if meta.name == "ABCMeta" and meta.root().name in ABC_MODULES:
             return True
 
-    for ancestor in node.ancestors():
-        if ancestor.name == "ABC" and ancestor.root().name in ABC_MODULES:
-            # abc.ABC inheritance
+    # As well as direct abc.ABC inheritance
+    for base in node.bases:
+        inferred_base = safe_infer(base)
+        if (
+            isinstance(inferred_base, nodes.ClassDef)
+            and inferred_base.root().name in ABC_MODULES
+            and inferred_base.name == "ABC"
+        ):
             return True
 
     for method in node.methods():

pylint/testutils/lint_module_test.py

@@ -272,10 +272,15 @@
         )
         if missing:
             msg.append("\nExpected in testdata:")
-            msg.extend(f" {msg[0]:3}: {msg[1]}" for msg in sorted(missing))
+            msg.extend(
+                f" {msg[0]:3}: {msg[1]} ({cnt})" for msg, cnt in sorted(missing.items())
+            )
         if unexpected:
             msg.append("\nUnexpected in testdata:")
-            msg.extend(f" {msg[0]:3}: {msg[1]}" for msg in sorted(unexpected))
+            msg.extend(
+                f" {msg[0]:3}: {msg[1]} ({cnt})"
+                for msg, cnt in sorted(unexpected.items())
+            )
         error_msg = "\n".join(msg)
         if self._config and self._config.getoption("verbose") > 0:
             error_msg += "\n\nActual pylint output for this file:\n"

tests/functional/a/abstract/abstract_method.py

@@ -6,7 +6,7 @@
 import abc
 
 
-class Abstract:
+class Abstract(abc.ABC):
     def aaaa(self):
         """should be overridden in concrete class"""
         raise NotImplementedError()
@@ -16,7 +16,7 @@ def bbbb(self):
         raise NotImplementedError()
 
 
-class AbstractB(Abstract):
+class AbstractB(Abstract, abc.ABC):
     """Abstract class.
 
     this class is checking that it does not output an error msg for
@@ -44,12 +44,43 @@ class AbstractD(AbstractB, metaclass=abc.ABCMeta):
     """
 
 
-class Concrete(Abstract): # [abstract-method]
-    """Concrete class"""
+class ConcreteA(AbstractC):  # [abstract-method, abstract-method, abstract-method]
+    """
+    Incomplete concrete class.
+
+    Should trigger a warning for unimplemented abstract
+    methods due to lack of explicit abc.ABC inheritance.
+    """
+
+
+class ConcreteB(Abstract):  # [abstract-method]
+    """
+    Incomplete concrete class.
+
+    Should trigger a warning for unimplemented abstract
+    methods due to lack of explicit abc.ABC inheritance.
+    """
+
+    def aaaa(self):
+        """overridden form Abstract"""
+
 
+class ConcreteC(AbstractC):
+    """
+    Complete concrete class
+
+    Should not trigger a warning as all
+    abstract methods are implemented.
+    """
     def aaaa(self):
         """overridden form Abstract"""
 
+    def bbbb(self):
+        """overridden form Abstract"""
+
+    def cccc(self):
+        """overridden form AbstractB"""
+
 
 class Structure(metaclass=abc.ABCMeta):
     @abc.abstractmethod

tests/functional/a/abstract/abstract_method.txt

@@ -1,16 +1,19 @@
-abstract-method:47:0:47:14:Concrete:Method 'bbbb' is abstract in class 'Abstract' but is not overridden in child class 'Concrete':INFERENCE
-abstract-method:70:0:70:15:Container:Method '__hash__' is abstract in class 'Structure' but is not overridden in child class 'Container':INFERENCE
-abstract-method:70:0:70:15:Container:Method '__iter__' is abstract in class 'Structure' but is not overridden in child class 'Container':INFERENCE
-abstract-method:70:0:70:15:Container:Method '__len__' is abstract in class 'Structure' but is not overridden in child class 'Container':INFERENCE
-abstract-method:76:0:76:13:Sizable:Method '__contains__' is abstract in class 'Structure' but is not overridden in child class 'Sizable':INFERENCE
-abstract-method:76:0:76:13:Sizable:Method '__hash__' is abstract in class 'Structure' but is not overridden in child class 'Sizable':INFERENCE
-abstract-method:76:0:76:13:Sizable:Method '__iter__' is abstract in class 'Structure' but is not overridden in child class 'Sizable':INFERENCE
-abstract-method:82:0:82:14:Hashable:Method '__contains__' is abstract in class 'Structure' but is not overridden in child class 'Hashable':INFERENCE
-abstract-method:82:0:82:14:Hashable:Method '__iter__' is abstract in class 'Structure' but is not overridden in child class 'Hashable':INFERENCE
-abstract-method:82:0:82:14:Hashable:Method '__len__' is abstract in class 'Structure' but is not overridden in child class 'Hashable':INFERENCE
-abstract-method:87:0:87:14:Iterator:Method '__contains__' is abstract in class 'Structure' but is not overridden in child class 'Iterator':INFERENCE
-abstract-method:87:0:87:14:Iterator:Method '__hash__' is abstract in class 'Structure' but is not overridden in child class 'Iterator':INFERENCE
-abstract-method:87:0:87:14:Iterator:Method '__len__' is abstract in class 'Structure' but is not overridden in child class 'Iterator':INFERENCE
-abstract-method:106:0:106:19:BadComplexMro:Method '__hash__' is abstract in class 'Structure' but is not overridden in child class 'BadComplexMro':INFERENCE
-abstract-method:106:0:106:19:BadComplexMro:Method '__len__' is abstract in class 'AbstractSizable' but is not overridden in child class 'BadComplexMro':INFERENCE
-abstract-method:106:0:106:19:BadComplexMro:Method 'length' is abstract in class 'AbstractSizable' but is not overridden in child class 'BadComplexMro':INFERENCE
+abstract-method:47:0:47:15:ConcreteA:Method 'aaaa' is abstract in class 'Abstract' but is not overridden in child class 'ConcreteA':INFERENCE
+abstract-method:47:0:47:15:ConcreteA:Method 'bbbb' is abstract in class 'Abstract' but is not overridden in child class 'ConcreteA':INFERENCE
+abstract-method:47:0:47:15:ConcreteA:Method 'cccc' is abstract in class 'AbstractB' but is not overridden in child class 'ConcreteA':INFERENCE
+abstract-method:56:0:56:15:ConcreteB:Method 'bbbb' is abstract in class 'Abstract' but is not overridden in child class 'ConcreteB':INFERENCE
+abstract-method:101:0:101:15:Container:Method '__hash__' is abstract in class 'Structure' but is not overridden in child class 'Container':INFERENCE
+abstract-method:101:0:101:15:Container:Method '__iter__' is abstract in class 'Structure' but is not overridden in child class 'Container':INFERENCE
+abstract-method:101:0:101:15:Container:Method '__len__' is abstract in class 'Structure' but is not overridden in child class 'Container':INFERENCE
+abstract-method:107:0:107:13:Sizable:Method '__contains__' is abstract in class 'Structure' but is not overridden in child class 'Sizable':INFERENCE
+abstract-method:107:0:107:13:Sizable:Method '__hash__' is abstract in class 'Structure' but is not overridden in child class 'Sizable':INFERENCE
+abstract-method:107:0:107:13:Sizable:Method '__iter__' is abstract in class 'Structure' but is not overridden in child class 'Sizable':INFERENCE
+abstract-method:113:0:113:14:Hashable:Method '__contains__' is abstract in class 'Structure' but is not overridden in child class 'Hashable':INFERENCE
+abstract-method:113:0:113:14:Hashable:Method '__iter__' is abstract in class 'Structure' but is not overridden in child class 'Hashable':INFERENCE
+abstract-method:113:0:113:14:Hashable:Method '__len__' is abstract in class 'Structure' but is not overridden in child class 'Hashable':INFERENCE
+abstract-method:118:0:118:14:Iterator:Method '__contains__' is abstract in class 'Structure' but is not overridden in child class 'Iterator':INFERENCE
+abstract-method:118:0:118:14:Iterator:Method '__hash__' is abstract in class 'Structure' but is not overridden in child class 'Iterator':INFERENCE
+abstract-method:118:0:118:14:Iterator:Method '__len__' is abstract in class 'Structure' but is not overridden in child class 'Iterator':INFERENCE
+abstract-method:137:0:137:19:BadComplexMro:Method '__hash__' is abstract in class 'Structure' but is not overridden in child class 'BadComplexMro':INFERENCE
+abstract-method:137:0:137:19:BadComplexMro:Method '__len__' is abstract in class 'AbstractSizable' but is not overridden in child class 'BadComplexMro':INFERENCE
+abstract-method:137:0:137:19:BadComplexMro:Method 'length' is abstract in class 'AbstractSizable' but is not overridden in child class 'BadComplexMro':INFERENCE