Fix #6588: autodoc: Decorated inherited method has no documentation

CHANGES

@@ -68,6 +68,7 @@ Bugs fixed
 
 * #6703: autodoc: incremental build does not work for imported objects
 * #7564: autodoc: annotations not to be shown for descriptors
+* #6588: autodoc: Decorated inherited method has no documentation
 * #7535: sphinx-autogen: crashes when custom template uses inheritance
 * #7536: sphinx-autogen: crashes when template uses i18n feature
 

sphinx/ext/autodoc/__init__.py

@@ -436,7 +436,8 @@ class Documenter:
                           % self.__class__.__name__,
                           RemovedInSphinx40Warning)
         docstring = getdoc(self.object, self.get_attr,
-                           self.env.config.autodoc_inherit_docstrings)
+                           self.env.config.autodoc_inherit_docstrings,
+                           self.parent, self.object_name)
         if docstring:
             tab_width = self.directive.state.document.settings.tab_width
             return [prepare_docstring(docstring, ignore, tab_width)]
@@ -557,7 +558,8 @@ class Documenter:
             else:
                 isattr = False
 
-            doc = getdoc(member, self.get_attr, self.env.config.autodoc_inherit_docstrings)
+            doc = getdoc(member, self.get_attr, self.env.config.autodoc_inherit_docstrings,
+                         self.parent, self.object_name)
             if not isinstance(doc, str):
                 # Ignore non-string __doc__
                 doc = None
@@ -1250,7 +1252,8 @@ class ClassDocumenter(DocstringSignatureMixin, ModuleLevelDocumenter):  # type:
         if content in ('both', 'init'):
             __init__ = self.get_attr(self.object, '__init__', None)
             initdocstring = getdoc(__init__, self.get_attr,
-                                   self.env.config.autodoc_inherit_docstrings)
+                                   self.env.config.autodoc_inherit_docstrings,
+                                   self.parent, self.object_name)
             # for new-style classes, no __init__ means default __init__
             if (initdocstring is not None and
                 (initdocstring == object.__init__.__doc__ or  # for pypy
@@ -1260,7 +1263,8 @@ class ClassDocumenter(DocstringSignatureMixin, ModuleLevelDocumenter):  # type:
                 # try __new__
                 __new__ = self.get_attr(self.object, '__new__', None)
                 initdocstring = getdoc(__new__, self.get_attr,
-                                       self.env.config.autodoc_inherit_docstrings)
+                                       self.env.config.autodoc_inherit_docstrings,
+                                       self.parent, self.object_name)
                 # for new-style classes, no __new__ means default __new__
                 if (initdocstring is not None and
                     (initdocstring == object.__new__.__doc__ or  # for pypy

sphinx/util/inspect.py

@@ -691,13 +691,14 @@ class Signature:
 
 
 def getdoc(obj: Any, attrgetter: Callable = safe_getattr,
-           allow_inherited: bool = False) -> str:
+           allow_inherited: bool = False, cls: Any = None, name: str = None) -> str:
     """Get the docstring for the object.
 
     This tries to obtain the docstring for some kind of objects additionally:
 
     * partial functions
     * inherited docstring
+    * inherited decorated methods
     """
     doc = attrgetter(obj, '__doc__', None)
     if ispartial(obj) and doc == obj.__class__.__doc__:
@@ -705,4 +706,14 @@ def getdoc(obj: Any, attrgetter: Callable = safe_getattr,
     elif doc is None and allow_inherited:
         doc = inspect.getdoc(obj)
 
+        if doc is None and cls:
+            # inspect.getdoc() does not support some kind of inherited and decorated methods.
+            # This tries to obtain the docstring from super classes.
+            for basecls in getattr(cls, '__mro__', []):
+                meth = safe_getattr(basecls, name, None)
+                if meth:
+                    doc = inspect.getdoc(meth)
+                    if doc:
+                        break
+
     return doc

tests/test_util_inspect.py

@@ -564,3 +564,18 @@ def test_unpartial():
 
     assert inspect.unpartial(func2) is func1
     assert inspect.unpartial(func3) is func1
+
+
+def test_getdoc_inherited_decorated_method():
+    class Foo:
+        def meth(self):
+            """docstring."""
+
+    class Bar(Foo):
+        @functools.lru_cache()
+        def meth(self):
+            # inherited and decorated method
+            pass
+
+    assert inspect.getdoc(Bar.meth, getattr, False, Bar, "meth") is None
+    assert inspect.getdoc(Bar.meth, getattr, True, Bar, "meth") == "docstring."