Added cascading deletes

Also ensured that unsetting works when not the default value of a field

docs/changelog.rst

@@ -5,6 +5,7 @@ Changelog
 Changes in dev
 ==============
 
+- Added cascading saves - so changes to Referenced documents are saved on .save()
 - Added select_related() support
 - Added support for the positional operator
 - Updated geo index checking to be recursive and check in embedded documents

mongoengine/base.py

@@ -747,10 +747,21 @@ class BaseDocument(object):
             if '_id' in set_data:
                 del(set_data['_id'])
 
-        for k,v in set_data.items():
-            if not v:
-                del(set_data[k])
-                unset_data[k] = 1
+        # Determine if any changed items were actually unset.
+        for path, value in set_data.items():
+            if value:
+                continue
+
+            # If we've set a value that aint the default value save it.
+            if path in self._fields:
+                default = self._fields[path].default
+                if callable(default):
+                    default = default()
+                if default != value:
+                    continue
+
+            del(set_data[path])
+            unset_data[path] = 1
         return set_data, unset_data
 
     @classmethod

mongoengine/document.py

@@ -112,7 +112,7 @@ class Document(BaseDocument):
                 self._collection = db[collection_name]
         return self._collection
 
-    def save(self, safe=True, force_insert=False, validate=True, write_options=None):
+    def save(self, safe=True, force_insert=False, validate=True, write_options=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.
@@ -131,6 +131,8 @@ class Document(BaseDocument):
                 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.
         """
+        from fields import ReferenceField, GenericReferenceField
+
         signals.pre_save.send(self.__class__, document=self)
 
         if validate:
@@ -140,6 +142,7 @@ class Document(BaseDocument):
             write_options = {}
 
         doc = self.to_mongo()
+
         created = '_id' not in doc
         try:
             collection = self.__class__.objects._collection
@@ -154,6 +157,18 @@ class Document(BaseDocument):
                     collection.update({'_id': object_id}, {"$set": updates}, upsert=True, safe=safe, **write_options)
                 if removals:
                     collection.update({'_id': object_id}, {"$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)
+
         except pymongo.errors.OperationFailure, err:
             message = 'Could not save document (%s)'
             if u'duplicate key' in unicode(err):

tests/document.py

@@ -1054,11 +1054,11 @@ class DocumentTest(unittest.TestCase):
 
         Person.drop_collection()
 
-        p1 = Person(name="Wilson Jr")
+        p1 = Person(name="Wilson Snr")
         p1.parent = None
         p1.save()
 
-        p2 = Person(name="Wilson Jr2")
+        p2 = Person(name="Wilson Jr")
         p2.parent = p1
         p2.save()
 
@@ -1071,6 +1071,51 @@ class DocumentTest(unittest.TestCase):
         p0.name = 'wpjunior'
         p0.save()
 
+    def test_save_cascades(self):
+
+        class Person(Document):
+            name = StringField()
+            parent = ReferenceField('self')
+
+        Person.drop_collection()
+
+        p1 = Person(name="Wilson Snr")
+        p1.parent = None
+        p1.save()
+
+        p2 = Person(name="Wilson Jr")
+        p2.parent = p1
+        p2.save()
+
+        p = Person.objects(name="Wilson Jr").get()
+        p.parent.name = "Daddy Wilson"
+        p.save()
+
+        p1.reload()
+        self.assertEquals(p1.name, p.parent.name)
+
+    def test_save_cascades_generically(self):
+
+        class Person(Document):
+            name = StringField()
+            parent = GenericReferenceField()
+
+        Person.drop_collection()
+
+        p1 = Person(name="Wilson Snr")
+        p1.save()
+
+        p2 = Person(name="Wilson Jr")
+        p2.parent = p1
+        p2.save()
+
+        p = Person.objects(name="Wilson Jr").get()
+        p.parent.name = "Daddy Wilson"
+        p.save()
+
+        p1.reload()
+        self.assertEquals(p1.name, p.parent.name)
+
     def test_update(self):
         """Ensure that an existing document is updated instead of be overwritten.
         """
@@ -1364,22 +1409,31 @@ class DocumentTest(unittest.TestCase):
         """Ensure save only sets / unsets changed fields
         """
 
+        class User(self.Person):
+            active = BooleanField(default=True)
+
+
+        User.drop_collection()
+
         # Create person object and save it to the database
-        person = self.Person(name='Test User', age=30)
-        person.save()
-        person.reload()
+        user = User(name='Test User', age=30, active=True)
+        user.save()
+        user.reload()
 
+        # Simulated Race condition
         same_person = self.Person.objects.get()
+        same_person.active = False
+
+        user.age = 21
+        user.save()
 
-        person.age = 21
         same_person.name = 'User'
-
-        person.save()
         same_person.save()
 
         person = self.Person.objects.get()
         self.assertEquals(person.name, 'User')
         self.assertEquals(person.age, 21)
+        self.assertEquals(person.active, False)
 
     def test_delete(self):
         """Ensure that document may be deleted using the delete method.