Fix #4415: autodoc classifies inherited classmethods as regular methods

CHANGES

@@ -16,6 +16,8 @@ Features added
 Bugs fixed
 ----------
 
+* #4415: autodoc classifies inherited classmethods as regular methods
+
 Testing
 --------
 

sphinx/ext/autodoc/__init__.py

@@ -32,7 +32,7 @@ from sphinx.application import ExtensionError
 from sphinx.util import logging
 from sphinx.util.inspect import Signature, isdescriptor, safe_getmembers, \
     safe_getattr, object_description, is_builtin_class_method, \
-    isenumattribute, getdoc
+    isenumattribute, isclassmethod, getdoc
 from sphinx.util.docstrings import prepare_docstring
 
 if False:
@@ -1261,8 +1261,10 @@ class MethodDocumenter(DocstringSignatureMixin, ClassLevelDocumenter):  # type:
 
         # to distinguish classmethod/staticmethod
         obj = self.parent.__dict__.get(self.object_name)
+        if obj is None:
+            obj = self.object
 
-        if isinstance(obj, classmethod):
+        if isclassmethod(obj):
             self.directivetype = 'classmethod'
             # document class and static members before ordinary ones
             self.member_order = self.member_order - 1

sphinx/util/inspect.py

@@ -154,6 +154,20 @@ def isenumattribute(x):
     return isinstance(x, enum.Enum)
 
 
+def isclassmethod(obj):
+    # type: (Any) -> bool
+    """Check if the object is classmethod."""
+    if isinstance(obj, classmethod):
+        return True
+    elif inspect.ismethod(obj):
+        if getattr(obj, 'im_self', None):  # py2
+            return True
+        elif getattr(obj, '__self__', None):  # py3
+            return True
+
+    return False
+
+
 def isdescriptor(x):
     # type: (Any) -> bool
     """Check if the object is some kind of descriptor."""

tests/roots/test-ext-autodoc/target/__init__.py

@@ -64,6 +64,10 @@ class Base(object):
     def inheritedmeth(self):
         """Inherited function."""
 
+    @classmethod
+    def inheritedclassmeth(cls):
+        """Inherited class method."""
+
 
 class Derived(Base):
     def inheritedmeth(self):

tests/test_autodoc.py

@@ -715,6 +715,7 @@ def test_generate():
     assert_processes(should, 'class', 'Class')
     options.inherited_members = True
     should.append(('method', 'target.Class.inheritedmeth'))
+    should.append(('method', 'target.Class.inheritedclassmeth'))
     assert_processes(should, 'class', 'Class')
 
     # test special members
@@ -798,6 +799,7 @@ def test_generate():
                   '   .. py:attribute:: Class.inst_attr_comment',
                   '   .. py:attribute:: Class.inst_attr_string',
                   '   .. py:attribute:: Class._private_inst_attr',
+                  '   .. py:classmethod:: Class.inheritedclassmeth()',
                   '   .. py:method:: Class.inheritedmeth()',
                   ],
                  'class', 'Class', member_order='bysource', all_members=True)