Move reset of cached_tag_flat_dict out of GroupableMixin into Tag.

That should not have been there!
Needed to add the BAIL sentinel so that Tag methods would only
reset the cache if the internal method actually did made any changes.

etiquette/objects.py

@@ -10,6 +10,7 @@ import traceback
 
 from voussoirkit import bytestring
 from voussoirkit import pathclass
+from voussoirkit import sentinel
 from voussoirkit import spinal
 from voussoirkit import sqlhelpers
 
@@ -19,6 +20,8 @@ from . import exceptions
 from . import helpers
 
 
+BAIL = sentinel.Sentinel('BAIL')
+
 def normalize_db_row(db_row, table):
     if isinstance(db_row, (list, tuple)):
         db_row = dict(zip(constants.SQL_COLUMNS[table], db_row))
@@ -98,7 +101,7 @@ class GroupableMixin:
             raise exceptions.CantGroupSelf(self)
 
         if self.has_child(member):
-            return
+            return BAIL
 
         self.photodb.log.debug('Adding child %s to %s.', member, self)
 
@@ -112,14 +115,12 @@ class GroupableMixin:
         }
         self.photodb.sql_insert(table=self.group_table, data=data)
 
-        self.photodb._cached_tag_flat_dict = None
-
     def add_child(self, member):
         return self._add_child(member)
 
     def add_children(self, members):
-        for member in members:
-            self._add_child(member)
+        if all(self._add_child(member) is BAIL for member in members):
+            return BAIL
 
     def assert_same_type(self, other):
         if not isinstance(other, type(self)):
@@ -140,7 +141,6 @@ class GroupableMixin:
             If True, all children will be deleted.
             Otherwise they'll just be raised up one level.
         '''
-        self.photodb._cached_tag_flat_dict = None
         if delete_children:
             for child in self.get_children():
                 child.delete(delete_children=True)
@@ -191,7 +191,7 @@ class GroupableMixin:
 
     def remove_child(self, member):
         if not self.has_child(member):
-            return
+            return BAIL
 
         self.photodb.log.debug('Removing child %s from %s.', member, self)
 
@@ -200,7 +200,6 @@ class GroupableMixin:
             'memberid': member.id,
         }
         self.photodb.sql_delete(table=self.group_table, pairs=pairs)
-        self.photodb._cached_tag_flat_dict = None
 
     def walk_children(self):
         '''
@@ -1203,12 +1202,20 @@ class Tag(ObjectBase, GroupableMixin):
     @decorators.required_feature('tag.edit')
     @decorators.transaction
     def add_child(self, *args, **kwargs):
-        return super().add_child(*args, **kwargs)
+        ret = super().add_child(*args, **kwargs)
+        if ret is BAIL:
+            return
+        self.photodb._cached_tag_flat_dict = None
+        return ret
 
     @decorators.required_feature('tag.edit')
     @decorators.transaction
     def add_children(self, *args, **kwargs):
-        return super().add_children(*args, **kwargs)
+        ret = super().add_children(*args, **kwargs)
+        if ret is BAIL:
+            return
+        self.photodb._cached_tag_flat_dict = None
+        return ret
 
     @decorators.required_feature('tag.edit')
     @decorators.transaction
@@ -1299,10 +1306,11 @@ class Tag(ObjectBase, GroupableMixin):
     def delete(self, *, delete_children=False):
         self.photodb.log.debug('Deleting %s', self)
         self.photodb._cached_tag_flat_dict = None
-        GroupableMixin.delete(self, delete_children=delete_children)
+        super().delete(delete_children=delete_children)
         self.photodb.sql_delete(table='photo_tag_rel', pairs={'tagid': self.id})
         self.photodb.sql_delete(table='tag_synonyms', pairs={'mastername': self.name})
         self.photodb.sql_delete(table='tags', pairs={'id': self.id})
+        self.photodb._cached_tag_flat_dict = None
         self._uncache()
 
     @decorators.required_feature('tag.edit')
@@ -1335,7 +1343,11 @@ class Tag(ObjectBase, GroupableMixin):
     @decorators.required_feature('tag.edit')
     @decorators.transaction
     def remove_child(self, *args, **kwargs):
-        return super().remove_child(*args, **kwargs)
+        ret = super().remove_child(*args, **kwargs)
+        if ret is BAIL:
+            return
+        self.photodb._cached_tag_flat_dict = None
+        return ret
 
     @decorators.required_feature('tag.edit')
     @decorators.transaction