Improve weakref.proxy implementation for embedded documents

Author: bagerard

mongoengine/base/datastructures.py

@@ -117,6 +117,7 @@ def __init__(self, list_items, instance, name):
                 self._instance = instance
             else:
                 self._instance = weakref.proxy(instance)
+
         self._name = name
         super().__init__(list_items)
 
@@ -189,13 +190,6 @@ def _mark_as_changed(self, key=None):
 
 
 class EmbeddedDocumentList(BaseList):
-    def __init__(self, list_items, instance, name):
-        super().__init__(list_items, instance, name)
-        if isinstance(instance, weakref.ProxyTypes):
-            self._instance = instance
-        else:
-            self._instance = weakref.proxy(instance)
-
     @classmethod
     def __match_all(cls, embedded_doc, kwargs):
         """Return True if a given embedded doc matches all the filter

tests/fields/test_embedded_document_field.py

@@ -1,3 +1,4 @@
+import weakref
 from copy import deepcopy
 
 import pytest
@@ -62,6 +63,21 @@ class MyFailingDoc(Document):
             class MyFailingdoc2(Document):
                 emb = EmbeddedDocumentField("MyDoc")
 
+    def test_embedded_document_field_has_a_weakref__instance_reference(self):
+        class Wallet(EmbeddedDocument):
+            money = IntField()
+
+        class WalletOwner(Document):
+            name = StringField()
+            wallet = EmbeddedDocumentField(Wallet)
+
+        WalletOwner.drop_collection()
+
+        wallet = Wallet(money=100)
+        owner = WalletOwner(name="John", wallet=wallet)
+        assert wallet._instance is owner
+        assert isinstance(wallet._instance, weakref.ProxyTypes)
+
     def test_embedded_document_field_validate_subclass(self):
         class BaseItem(EmbeddedDocument):
             f = IntField()