Fix documentation of descriptor classes that have a custom metaclass

(i.e. a subclass of type).  This avoids using string comparisons to do
type checks, except in the case of the fix for #1155, since in Python 3
there really seems to be no way to export the instancemethod type, short
of using ctypes.

sphinx/ext/autodoc.py

@@ -34,6 +34,11 @@ from sphinx.util.inspect import getargspec, isdescriptor, safe_getmembers, \
 from sphinx.util.docstrings import prepare_docstring
 
 
+# This type isn't exposed directly in any modules, but can be found
+# here in most Python versions
+MethodDescriptorType = type(type.__subclasses__)
+
+
 #: extended signature RE: with explicit module name separated by ::
 py_ext_sig_re = re.compile(
     r'''^ ([\w.]+::)?            # explicit module name
@@ -1309,10 +1314,13 @@ class AttributeDocumenter(DocstringStripSignatureMixin, ClassLevelDocumenter):
 
     @classmethod
     def can_document_member(cls, member, membername, isattr, parent):
+        non_attr_types = cls.method_types + (type, MethodDescriptorType)
         isdatadesc = isdescriptor(member) and not \
-            isinstance(member, cls.method_types) and not \
-            type(member).__name__ in ("type", "method_descriptor",
-                                      "instancemethod")
+            isinstance(member, non_attr_types) and not \
+            type(member).__name__ == "instancemethod"
+        # That last condition addresses an obscure case of C-defined
+        # methods using a deprecated type in Python 3, that is not otherwise
+        # exported anywhere by Python
         return isdatadesc or (not isinstance(parent, ModuleDocumenter) and
                               not inspect.isroutine(member) and
                               not isinstance(member, class_types))

tests/test_autodoc.py

@@ -14,7 +14,7 @@
 from util import TestApp, Struct, raises
 from nose.tools import with_setup
 
-from six import StringIO
+from six import StringIO, add_metaclass
 from docutils.statemachine import ViewList
 
 from sphinx.ext.autodoc import AutoDirective, add_documenter, \
@@ -784,11 +784,13 @@ def test_generate():
     del directive.env.ref_context['py:module']
 
     # test descriptor class documentation
-    options.members = ['CustomDataDescriptor']
+    options.members = ['CustomDataDescriptor', 'CustomDataDescriptor2']
     assert_result_contains('.. py:class:: CustomDataDescriptor(doc)',
                            'module', 'test_autodoc')
     assert_result_contains('   .. py:method:: CustomDataDescriptor.meth()',
                            'module', 'test_autodoc')
+    assert_result_contains('.. py:class:: CustomDataDescriptor2(doc)',
+                           'module', 'test_autodoc')
 
 # --- generate fodder ------------
 
@@ -818,6 +820,15 @@ class CustomDataDescriptor(object):
         """Function."""
         return "The Answer"
 
+
+class CustomDataDescriptorMeta(type):
+    """Descriptor metaclass docstring."""
+
+@add_metaclass(CustomDataDescriptorMeta)
+class CustomDataDescriptor2(CustomDataDescriptor):
+    """Descriptor class with custom metaclass docstring."""
+
+
 def _funky_classmethod(name, b, c, d, docstring=None):
     """Generates a classmethod for a class from a template by filling out
     some arguments."""