mro() can be computed for classes with old style classes in the hierarchy

Author: PCManticore

ChangeLog

@@ -5,6 +5,8 @@ Change log for the astroid package (used to be astng)
 
    * Basic support for the class form of typing.NamedTuple
 
+   * mro() can be computed for classes with old style classes in the hierarchy
+
 
 2017-04-13 -- 1.5.0
 

astroid/scoped_nodes.py

@@ -1777,25 +1777,15 @@ def _inferred_bases(self, context=None):
                 for base in baseobj.bases:
                     yield base
 
-    def mro(self, context=None):
-        """Get the method resolution order, using C3 linearization.
-
-        It returns the list of ancestors sorted by the mro.
-        This will raise `NotImplementedError` for old-style classes, since
-        they don't have the concept of MRO.
-        """
-        if not self.newstyle:
-            raise NotImplementedError(
-                "Could not obtain mro for old-style classes.")
-
+    def _compute_mro(self, context=None):
         inferred_bases = list(self._inferred_bases(context=context))
         bases_mro = []
         for base in inferred_bases:
             if base is self:
                 continue
 
             try:
-                mro = base.mro(context=context)
+                mro = base._compute_mro(context=context)
                 bases_mro.append(mro)
             except NotImplementedError:
                 # Some classes have in their ancestors both newstyle and
@@ -1810,6 +1800,20 @@ def mro(self, context=None):
         _verify_duplicates_mro(unmerged_mro, self, context)
         return _c3_merge(unmerged_mro, self, context)
 
+    def mro(self, context=None):
+        """Get the method resolution order, using C3 linearization.
+
+        It returns the list of ancestors sorted by the mro.
+        This will raise `NotImplementedError` for old-style classes, since
+        they don't have the concept of MRO.
+        """
+
+        if not self.newstyle:
+            raise NotImplementedError(
+                "Could not obtain mro for old-style classes.")
+
+        return self._compute_mro(context=context)
+
     def bool_value(self):
         return True
 

astroid/tests/unittest_scoped_nodes.py

@@ -1323,6 +1323,33 @@ class Old: pass""")
         self.assertEqual(str(cm.exception), "Could not obtain mro for "
                                             "old-style classes.")
 
+    @test_utils.require_version(maxver='3.0')
+    def test_mro_for_classes_with_old_style_in_mro(self):
+        node = builder.extract_node('''
+        class Factory:
+            pass
+        class ClientFactory(Factory):
+            pass
+        class ReconnectingClientFactory(ClientFactory):
+            pass
+        class WebSocketAdapterFactory(object):
+            pass
+        class WebSocketClientFactory(WebSocketAdapterFactory, ClientFactory):
+            pass
+        class WampWebSocketClientFactory(WebSocketClientFactory):
+            pass
+        class RetryFactory(WampWebSocketClientFactory, ReconnectingClientFactory):
+            pas
+        ''')
+        self.assertEqualMro(
+            node,
+            ['RetryFactory', 'WampWebSocketClientFactory',
+             'WebSocketClientFactory', 'WebSocketAdapterFactory', 'object',
+             'ReconnectingClientFactory', 'ClientFactory',
+             'Factory'
+             ]
+        )
+
     @test_utils.require_version(maxver='3.0')
     def test_combined_newstyle_oldstyle_in_mro(self):
         node = builder.extract_node('''