Improve PR django-polymorphic#24, also perform a parent test for left/right movements

Author: vdboor

polymorphic_tree/admin/parentadmin.py

@@ -217,13 +217,26 @@ def api_node_moved_view(self, request):
  'error': _('You do not have permission to move this node.')
  }), content_type='application/json', status=409)
 
+ # Find out which parent the node will reside under.
+ parent_attr_id = '{}_id'.format(moved._mptt_meta.parent_attr)
+
  if position == 'inside':
+ test_new_parent = target
+ else:
+ # left/right of an other node
+ if getattr(target, parent_attr_id) != getattr(moved, parent_attr_id):
+ test_new_parent = getattr(target, moved._mptt_meta.parent_attr)
+ else:
+ test_new_parent = None # kept inside the same parent.
+
+ # Test whether the parent allows this node to be a child.
+ if test_new_parent is not None:
  error = None
- if not self.can_have_children(target):
+ if not self.can_have_children(test_new_parent):
  error = _(u'Cannot place \u2018{0}\u2019 below \u2018{1}\u2019;'
  u' a {2} does not allow children!').format(moved, target,
  target._meta.verbose_name)
- elif not self.can_have_children(target, moved):
+ elif not self.can_have_children(test_new_parent, child=moved):
  error = _(u'Cannot place \u2018{0}\u2019 below \u2018{1}\u2019;'
  u' a {2} does not allow {3} as a child!').format(moved,
  target, target._meta.verbose_name, moved._meta.verbose_name)
@@ -235,7 +248,6 @@ def api_node_moved_view(self, request):
  }), content_type='application/json', status=409) # Conflict
 
  # Compare on strings to support UUID fields.
- parent_attr_id = '{}_id'.format(moved._mptt_meta.parent_attr)
  if str(getattr(moved, parent_attr_id)) != str(previous_parent_id):
  return HttpResponse(json.dumps({
  'action': 'reload',