bpo-40257: Revert changes to inspect.getdoc() (GH-20073)

Lib/pydoc.py

@@ -90,9 +90,101 @@ def pathdirs():
             normdirs.append(normdir)
     return dirs
 
+def _findclass(func):
+    cls = sys.modules.get(func.__module__)
+    if cls is None:
+        return None
+    for name in func.__qualname__.split('.')[:-1]:
+        cls = getattr(cls, name)
+    if not inspect.isclass(cls):
+        return None
+    return cls
+
+def _finddoc(obj):
+    if inspect.ismethod(obj):
+        name = obj.__func__.__name__
+        self = obj.__self__
+        if (inspect.isclass(self) and
+            getattr(getattr(self, name, None), '__func__') is obj.__func__):
+            # classmethod
+            cls = self
+        else:
+            cls = self.__class__
+    elif inspect.isfunction(obj):
+        name = obj.__name__
+        cls = _findclass(obj)
+        if cls is None or getattr(cls, name) is not obj:
+            return None
+    elif inspect.isbuiltin(obj):
+        name = obj.__name__
+        self = obj.__self__
+        if (inspect.isclass(self) and
+            self.__qualname__ + '.' + name == obj.__qualname__):
+            # classmethod
+            cls = self
+        else:
+            cls = self.__class__
+    # Should be tested before isdatadescriptor().
+    elif isinstance(obj, property):
+        func = obj.fget
+        name = func.__name__
+        cls = _findclass(func)
+        if cls is None or getattr(cls, name) is not obj:
+            return None
+    elif inspect.ismethoddescriptor(obj) or inspect.isdatadescriptor(obj):
+        name = obj.__name__
+        cls = obj.__objclass__
+        if getattr(cls, name) is not obj:
+            return None
+        if inspect.ismemberdescriptor(obj):
+            slots = getattr(cls, '__slots__', None)
+            if isinstance(slots, dict) and name in slots:
+                return slots[name]
+    else:
+        return None
+    for base in cls.__mro__:
+        try:
+            doc = _getowndoc(getattr(base, name))
+        except AttributeError:
+            continue
+        if doc is not None:
+            return doc
+    return None
+
+def _getowndoc(obj):
+    """Get the documentation string for an object if it is not
+    inherited from its class."""
+    try:
+        doc = object.__getattribute__(obj, '__doc__')
+        if doc is None:
+            return None
+        if obj is not type:
+            typedoc = type(obj).__doc__
+            if isinstance(typedoc, str) and typedoc == doc:
+                return None
+        return doc
+    except AttributeError:
+        return None
+
+def _getdoc(object):
+    """Get the documentation string for an object.
+
+    All tabs are expanded to spaces.  To clean up docstrings that are
+    indented to line up with blocks of code, any whitespace than can be
+    uniformly removed from the second line onwards is removed."""
+    doc = _getowndoc(object)
+    if doc is None:
+        try:
+            doc = _finddoc(object)
+        except (AttributeError, TypeError):
+            return None
+    if not isinstance(doc, str):
+        return None
+    return inspect.cleandoc(doc)
+
 def getdoc(object):
     """Get the doc string or comments for an object."""
-    result = inspect.getdoc(object) or inspect.getcomments(object)
+    result = _getdoc(object) or inspect.getcomments(object)
     return result and re.sub('^ *\n', '', result.rstrip()) or ''
 
 def splitdoc(doc):
@@ -1669,7 +1761,7 @@ def render_doc(thing, title='Python Library Documentation: %s', forceload=0,
               inspect.isclass(object) or
               inspect.isroutine(object) or
               inspect.isdatadescriptor(object) or
-              inspect.getdoc(object)):
+              _getdoc(object)):
         # If the passed object is a piece of data or an instance,
         # document its available methods instead of its value.
         if hasattr(object, '__origin__'):