Merge pull request #58 from sthenault/id0

Fix case where id are explicitly specified and starts by 0

sqlalchemy_mptt/events.py

@@ -88,7 +88,7 @@ def mptt_before_insert(mapper, connection, instance):
     db_pk = instance.get_pk_column()
     table_pk = getattr(table.c, db_pk.name)
 
-    if not instance.parent_id:
+    if instance.parent_id is None:
         instance.left = 1
         instance.right = 2
         instance.level = instance.get_default_level()
@@ -176,7 +176,7 @@ def mptt_before_delete(mapper, connection, instance, delete=True):
             )
         )
 
-    if instance.parent_id or not delete:
+    if instance.parent_id is not None or not delete:
         """ Update key of current tree
 
             UPDATE tree
@@ -358,14 +358,15 @@ def mptt_before_update(mapper, connection, instance):
     ).fetchone()
 
     # if instance just update w/o move
+    # XXX why this str() around parent_id comparison?
     if not left_sibling \
             and str(node_parent_id) == str(instance.parent_id) \
             and not mptt_move_inside:
         if left_sibling_tree_id is None:
             return
 
     # fix tree shorting
-    if instance.parent_id:
+    if instance.parent_id is not None:
         (
             parent_id,
             parent_pos_right,
@@ -385,14 +386,14 @@ def mptt_before_update(mapper, connection, instance):
                 table_pk == instance.parent_id
             )
         ).fetchone()
-        if not node_parent_id and node_tree_id == parent_tree_id:
+        if node_parent_id is None and node_tree_id == parent_tree_id:
             instance.parent_id = None
             return
 
     # delete from old tree
     mptt_before_delete(mapper, connection, instance, False)
 
-    if instance.parent_id:
+    if instance.parent_id is not None:
         """ Put there right position of new parent node (there moving node
             should be moved)
         """

sqlalchemy_mptt/tests/test_events.py

@@ -12,9 +12,12 @@
 
 import unittest
 
-from sqlalchemy import Column, Boolean, Integer
+from sqlalchemy import Column, Boolean, Integer, create_engine
 from sqlalchemy.event import contains
 from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy.orm import sessionmaker
+
+from sqlalchemy_mptt import mptt_sessionmaker
 
 from . import TreeTestingMixin
 from ..mixins import BaseNestedSets
@@ -150,3 +153,25 @@ def test_remove(self):
             )
         )
         tree_manager.register_events()
+
+
+class Tree0Id(unittest.TestCase):
+    """Test case where node id is provided and starts with 0
+
+    See comments in https://github.com/uralbash/sqlalchemy_mptt/issues/57
+    """
+    def test(self):
+        engine = create_engine('sqlite:///:memory:')
+        Session = mptt_sessionmaker(sessionmaker(bind=engine))
+        session = Session()
+        Base.metadata.create_all(engine)
+
+        root = Tree(id=0)
+        child = Tree(id=1, parent_id=0)
+
+        session.add(root)
+        session.add(child)
+        session.commit()
+
+        self.assertEqual(root.tree_id, 1)
+        self.assertEqual(child.tree_id, 1)