EmbeddedDocuments dont support Reverse Delete Rules

Now throws an InvalidDocumentError

Refs #227

docs/upgrade.rst

@@ -8,10 +8,11 @@ Upgrading
 Embedded Documents - if you had a `pk` field you will have to rename it from `_id`
 to `pk` as pk is no longer a property of Embedded Documents.
 
+Reverse Delete Rules in Embedded Documents, MapFields and DictFields now throw
+an InvalidDocument error as they aren't currently supported.
+
 Document._get_subclasses - Is no longer used and the class method has been removed.
 
-Reverse Delete Rules on MapFields and DictFields now throw a InvalidDocument error
-as they aren't supported.
 
 0.4 to 0.5
 ===========

mongoengine/base.py

@@ -518,6 +518,8 @@ class DocumentMetaclass(type):
                 f = field.field
 
             if delete_rule != DO_NOTHING:
+                if issubclass(new_class, EmbeddedDocument):
+                    raise InvalidDocumentError("Reverse delete rules are not supported for EmbeddedDocuments (field: %s)" % field.name)
                 f.document_type.register_delete_rule(new_class, field.name, delete_rule)
 
             if field.name and hasattr(Document, field.name) and EmbeddedDocument not in new_class.mro():
@@ -663,6 +665,18 @@ class TopLevelDocumentMetaclass(DocumentMetaclass):
 
         return new_class
 
+    def __instancecheck__(cls, inst):
+        """Custom instance check for isinstance() as registering delete rules or
+        calling a cls method in __new__ seems to change the cls so vanilla
+        isinstance() fails"""
+        is_instance = super(DocumentMetaclass, cls).__instancecheck__(inst)
+        if hasattr(cls, '_meta') and 'delete_rules' in cls._meta and not is_instance:
+            try:
+                is_instance = get_document(cls.__name__) == get_document(inst.__class__.__name__)
+            except NotRegistered:
+                pass
+        return is_instance
+
     @classmethod
     def _unique_with_indexes(cls, new_class, namespace=""):
         unique_indexes = []

tests/document.py

@@ -2245,6 +2245,8 @@ class DocumentTest(unittest.TestCase):
         author.delete()
         self.assertEqual(len(BlogPost.objects), 0)
 
+    def test_invalid_reverse_delete_rules_raise_errors(self):
+
         def throw_invalid_document_error():
             class Blog(Document):
                 content = StringField()
@@ -2253,6 +2255,12 @@ class DocumentTest(unittest.TestCase):
 
         self.assertRaises(InvalidDocumentError, throw_invalid_document_error)
 
+        def throw_invalid_document_error_embedded():
+            class Parents(EmbeddedDocument):
+                father = ReferenceField('Person', reverse_delete_rule=DENY)
+                mother = ReferenceField('Person', reverse_delete_rule=DENY)
+
+        self.assertRaises(InvalidDocumentError, throw_invalid_document_error_embedded)
 
     def test_reverse_delete_rule_cascade_recurs(self):
         """Ensure that a chain of documents is also deleted upon cascaded