refactor: remove noparent and just leave noop

ziggurat_foundations/__init__.py

@@ -17,7 +17,6 @@ def __nonzero__(self):
 
 
 noop = NOOP()
-noparent = NOOP()
 
 
 def make_passwordmanager():

ziggurat_foundations/models/services/resource_tree.py

@@ -1,6 +1,6 @@
 from __future__ import unicode_literals
 
-from ziggurat_foundations import noparent
+from ziggurat_foundations import noop
 
 __all__ = ['ResourceTreeService']
 
@@ -77,7 +77,7 @@ def path_upper(self, object_id, limit_depth=1000000, db_session=None, *args,
             object_id=object_id, limit_depth=limit_depth, db_session=db_session,
             *args, **kwargs)
 
-    def move_to_position(self, resource_id, to_position, new_parent_id=noparent,
+    def move_to_position(self, resource_id, to_position, new_parent_id=noop,
                          db_session=None, *args, **kwargs):
         """
         Moves node to new location in the tree

ziggurat_foundations/models/services/resource_tree_postgres.py

@@ -3,7 +3,7 @@
 from collections import OrderedDict
 
 import sqlalchemy as sa
-from ziggurat_foundations import noparent
+from ziggurat_foundations import noop
 from ziggurat_foundations.exc import (
     ZigguratResourceTreeMissingException,
     ZigguratResourceTreePathException,
@@ -171,7 +171,7 @@ def path_upper(cls, object_id, limit_depth=1000000, db_session=None, *args,
 
     @classmethod
     def move_to_position(cls, resource_id, to_position,
-                         new_parent_id=noparent, db_session=None, *args,
+                         new_parent_id=noop, db_session=None, *args,
                          **kwargs):
         """
         Moves node to new location in the tree
@@ -194,15 +194,15 @@ def move_to_position(cls, resource_id, to_position,
 
         # reset if parent is same as old
         if new_parent_id == resource.parent_id:
-            new_parent_id = noparent
+            new_parent_id = noop
 
-        if new_parent_id is not noparent:
+        if new_parent_id is not noop:
             cls.check_node_parent(resource_id, new_parent_id,
                                   db_session=db_session)
         else:
             same_branch = True
 
-        if new_parent_id is noparent:
+        if new_parent_id is noop:
             # it is not guaranteed that parent exists
             parent_id = resource.parent_id if resource else None
         else:
@@ -212,7 +212,7 @@ def move_to_position(cls, resource_id, to_position,
             parent_id, to_position, on_same_branch=same_branch,
             db_session=db_session)
         # move on same branch
-        if new_parent_id is noparent:
+        if new_parent_id is noop:
             order_range = list(sorted((resource.ordering, to_position)))
             move_down = resource.ordering > to_position
 
@@ -361,7 +361,7 @@ def check_node_position(
         :return:
         """
         db_session = get_db_session(db_session)
-        if position < 1:
+        if not position or position < 1:
             raise ZigguratResourceOutOfBoundaryException(
                 'Position is lower than {}', value=1)
         item_count = cls.count_children(parent_id, db_session=db_session)