Fixes #356 - Django 1.8 support.

mptt/managers.py

@@ -11,6 +11,7 @@
 
 from mptt.exceptions import CantDisableUpdates, InvalidMove
 from mptt.querysets import TreeQuerySet
+from mptt.utils import _get_tree_model
 
 __all__ = ('TreeManager',)
 
@@ -65,23 +66,7 @@ def contribute_to_class(self, model, name):
         super(TreeManager, self).contribute_to_class(model, name)
 
         if not (model._meta.abstract or model._meta.proxy):
-            # Find the model that contains the tree fields.
-            # This is a weird way of going about it, but Django doesn't let us access
-            # the fields list to detect where the tree fields actually are,
-            # because the app cache hasn't been loaded yet.
-            # So, it *should* be the *last* concrete MPTTModel subclass in the mro().
-            bases = list(model.mro())
-            while bases:
-                b = bases.pop()
-                # NOTE can't use `issubclass(b, MPTTModel)` here because we can't import MPTTModel yet!
-                # So hasattr(b, '_mptt_meta') will have to do.
-                if hasattr(b, '_mptt_meta') and not (b._meta.abstract or b._meta.proxy):
-                    break
-            else:
-                # this shouldn't ever happen! (fingers crossed ;)
-                raise TypeError("Couldn't find a concrete MPTTModel subclass in %s.mro()" % model)
-
-            self.tree_model = b
+            self.tree_model = _get_tree_model(model)
 
             self._base_manager = None
             if self.tree_model is not model:

mptt/models.py

@@ -13,6 +13,7 @@
 
 from mptt.fields import TreeForeignKey, TreeOneToOneField, TreeManyToManyField
 from mptt.managers import TreeManager
+from mptt.utils import _get_tree_model
 
 
 __all__ = (
@@ -307,11 +308,9 @@ def register(meta, cls, **kwargs):
                 bases.insert(0, MPTTModel)
                 cls.__bases__ = tuple(bases)
 
-            for key in ('left_attr', 'right_attr', 'tree_id_attr', 'level_attr'):
-                field_name = getattr(cls._mptt_meta, key)
-                try:
-                    cls._meta.get_field(field_name)
-                except models.FieldDoesNotExist:
+            if _get_tree_model(cls) is cls:
+                for key in ('left_attr', 'right_attr', 'tree_id_attr', 'level_attr'):
+                    field_name = getattr(cls._mptt_meta, key)
                     field = models.PositiveIntegerField(db_index=True, editable=False)
                     field.contribute_to_class(cls, field_name)
 

mptt/utils.py

@@ -175,3 +175,19 @@ def print_debug_info(qs, file=None):
             row.append(getattr(n, field))
         row.append('%s%s' % ('- ' * level, text_type(n).encode('utf-8')))
         writer.writerow(row)
+
+
+def _get_tree_model(model_class):
+    # Find the model that contains the tree fields.
+    # This is a weird way of going about it, but Django doesn't let us access
+    # the fields list to detect where the tree fields actually are,
+    # because the app cache hasn't been loaded yet.
+    # So, it *should* be the *last* concrete MPTTModel subclass in the mro().
+    bases = list(model_class.mro())
+    while bases:
+        b = bases.pop()
+        # NOTE can't use `issubclass(b, MPTTModel)` here because we can't import MPTTModel yet!
+        # So hasattr(b, '_mptt_meta') will have to do.
+        if hasattr(b, '_mptt_meta') and not (b._meta.abstract or b._meta.proxy):
+            return b
+    return None