Delete cascade cycle issue

AUTHORS

@@ -226,4 +226,4 @@ that much better:
  * Emmanuel Leblond (https://github.com/touilleMan)
  * Breeze.Kay (https://github.com/9nix00)
  * Vicki Donchenko (https://github.com/kivistein)
-
+ * Emile Caron (https://github.com/emilecaron)

docs/changelog.rst

@@ -34,6 +34,7 @@ Changes in 0.10.0
 - Allow dynamic lookup for more than two parts. #882
 - Added support for min_distance on geo queries. #831
 - Allow to add custom metadata to fields #705
+- Fix infinite recursion with CASCADE delete rules under specific conditions. #1046
 
 Changes in 0.9.0
 ================

mongoengine/queryset/base.py

@@ -363,11 +363,6 @@ def delete(self, write_concern=None, _from_doc_delete=False, cascade_refs=None):
         queryset = self.clone()
         doc = queryset._document
 
-        cascade_refs = set() if cascade_refs is None else cascade_refs
-        if doc in cascade_refs:
-            return 0
-        cascade_refs.add(doc)
-
         if write_concern is None:
             write_concern = {}
 
@@ -407,7 +402,10 @@ def delete(self, write_concern=None, _from_doc_delete=False, cascade_refs=None):
                 continue
             rule = doc._meta['delete_rules'][rule_entry]
             if rule == CASCADE:
-                ref_q = document_cls.objects(**{field_name + '__in': self})
+                cascade_refs = set() if cascade_refs is None else cascade_refs
+                for ref in queryset:
+                    cascade_refs.add(ref.id)
+                ref_q = document_cls.objects(**{field_name + '__in': self, 'id__nin': cascade_refs})
                 ref_q_count = ref_q.count()
                 if ref_q_count > 0:
                     ref_q.delete(write_concern=write_concern, cascade_refs=cascade_refs)