Add optimization: If conventional "objects" attr exists, just use tha…

…t and don't iterate everything else, also fixes #369

mptt/models.py

@@ -327,21 +327,27 @@ def register(meta, cls, **kwargs):
 
                 # make sure we have a tree manager somewhere
                 tree_manager = None
-                for attr in sorted(dir(cls)):
-                    try:
-                        # HACK: avoid using getattr(cls, attr)
-                        # because it calls __get__ on descriptors, which can cause nasty side effects
-                        # with more inconsiderate apps.
-                        # (e.g. django-tagging's TagField is a descriptor which can do db queries on getattr)
-                        # ( ref: http://stackoverflow.com/questions/27790344 )
-                        obj = cls.__dict__[attr]
-                    except KeyError:
-                        continue
-                    if isinstance(obj, TreeManager):
-                        tree_manager = obj
-                        # prefer any locally defined manager (i.e. keep going if not local)
-                        if obj.model is cls:
-                            break
+                attrs = dir(cls)
+                if "objects" in attrs and isinstance(cls.objects, TreeManager):
+                    tree_manager = cls.objects
+
+                # Go look for it somewhere else
+                else:
+                    for attr in sorted(attrs):
+                        try:
+                            # HACK: avoid using getattr(cls, attr)
+                            # because it calls __get__ on descriptors, which can cause nasty side effects
+                            # with more inconsiderate apps.
+                            # (e.g. django-tagging's TagField is a descriptor which can do db queries on getattr)
+                            # ( ref: http://stackoverflow.com/questions/27790344 )
+                            obj = cls.__dict__[attr]
+                        except KeyError:
+                            continue
+                        if isinstance(obj, TreeManager):
+                            tree_manager = obj
+                            # prefer any locally defined manager (i.e. keep going if not local)
+                            if obj.model is cls:
+                                break
                 if tree_manager and tree_manager.model is not cls:
                     tree_manager = tree_manager._copy_to_model(cls)
                 elif tree_manager is None: