Configurable cascading saves

Updated cascading save logic - can now add meta or pass
cascade to save().  Also Cleaned up reset changed fields logic
as well, so less looping

Refs: #370 #349

mongoengine/document.py

@@ -120,7 +120,8 @@ class Document(BaseDocument):
                 self._collection = db[collection_name]
         return self._collection
 
-    def save(self, safe=True, force_insert=False, validate=True, write_options=None, _refs=None):
+    def save(self, safe=True, force_insert=False, validate=True, write_options=None,
+            cascade=None, _refs=None):
         """Save the :class:`~mongoengine.Document` to the database. If the
         document already exists, it will be updated, otherwise it will be
         created.
@@ -138,14 +139,19 @@ class Document(BaseDocument):
                 which will be used as options for the resultant ``getLastError`` command.
                 For example, ``save(..., w=2, fsync=True)`` will wait until at least two servers
                 have recorded the write and will force an fsync on each server being written to.
+        :param cascade: Sets the flag for cascading saves.  You can set a default by setting
+            "cascade" in the document __meta__
+        :param _refs: A list of processed references used in cascading saves
 
         .. versionchanged:: 0.5
             In existing documents it only saves changed fields using set / unset
             Saves are cascaded and any :class:`~pymongo.dbref.DBRef` objects
             that have changes are saved as well.
-        """
-        from fields import ReferenceField, GenericReferenceField
+        .. versionchanged:: 0.6
+            Cascade saves are optional = defaults to True, if you want fine grain
+            control then you can turn off using document meta['cascade'] = False
 
+        """
         signals.pre_save.send(self.__class__, document=self)
 
         if validate:
@@ -173,16 +179,11 @@ class Document(BaseDocument):
                 if removals:
                     collection.update({'_id': object_id}, {"$unset": removals}, upsert=True, safe=safe, **write_options)
 
-            # Save any references / generic references
-            _refs = _refs or []
-            for name, cls in self._fields.items():
-                if isinstance(cls, (ReferenceField, GenericReferenceField)):
-                    ref = getattr(self, name)
-                    if ref and str(ref) not in _refs:
-                        _refs.append(str(ref))
-                        ref.save(safe=safe, force_insert=force_insert,
-                                 validate=validate, write_options=write_options,
-                                 _refs=_refs)
+            cascade = self._meta.get('cascade', True) if cascade is None else cascade
+            if cascade:
+                self.cascade_save(safe=safe, force_insert=force_insert,
+                                  validate=validate, write_options=write_options,
+                                  cascade=cascade, _refs=_refs)
 
         except pymongo.errors.OperationFailure, err:
             message = 'Could not save document (%s)'
@@ -192,23 +193,26 @@ class Document(BaseDocument):
         id_field = self._meta['id_field']
         self[id_field] = self._fields[id_field].to_python(object_id)
 
-        def reset_changed_fields(doc, inspected=None):
-            """Loop through and reset changed fields lists"""
-
-            inspected = inspected or []
-            inspected.append(doc)
-            if hasattr(doc, '_changed_fields'):
-                doc._changed_fields = []
-
-            for field_name in doc._fields:
-                field = getattr(doc, field_name)
-                if field not in inspected and hasattr(field, '_changed_fields'):
-                    reset_changed_fields(field, inspected)
-
-        reset_changed_fields(self)
         self._changed_fields = []
         signals.post_save.send(self.__class__, document=self, created=creation_mode)
 
+    def cascade_save(self, *args, **kwargs):
+        """Recursively saves any references / generic references on an object"""
+        from fields import ReferenceField, GenericReferenceField
+        _refs = kwargs.get('_refs', []) or []
+        for name, cls in self._fields.items():
+            if not isinstance(cls, (ReferenceField, GenericReferenceField)):
+                continue
+            ref = getattr(self, name)
+            if not ref:
+                continue
+            ref_id = "%s,%s" % (ref.__class__.__name__, str(ref._data))
+            if ref and ref_id not in _refs:
+                _refs.append(ref_id)
+                kwargs["_refs"] = _refs
+                ref.save(**kwargs)
+                ref._changed_fields = []
+
     def update(self, **kwargs):
         """Performs an update on the :class:`~mongoengine.Document`
         A convenience wrapper to :meth:`~mongoengine.QuerySet.update`.