Fix deepcopy on EmbeddedDocument

AUTHORS

@@ -260,3 +260,4 @@ that much better:
  * Stankiewicz Mateusz (https://github.com/mas15)
  * Felix Schultheiß (https://github.com/felix-smashdocs)
  * Jan Stein (https://github.com/janste63)
+ * Timothé Perez (https://github.com/AchilleAsh)

docs/changelog.rst

@@ -13,6 +13,7 @@ Changes in 0.23.1
 ===========
 - Bug fix: ignore LazyReferenceFields when clearing _changed_fields #2484
 - Improve connection doc #2481
+- Fix deepcopy on EmbeddedDocument
 
 Changes in 0.23.0
 =================

mongoengine/document.py

@@ -99,6 +99,15 @@ class EmbeddedDocument(BaseDocument, metaclass=DocumentMetaclass):
     def __ne__(self, other):
         return not self.__eq__(other)
 
+    def __getstate__(self):
+        data = super().__getstate__()
+        data["_instance"] = self._instance
+        return data
+
+    def __setstate__(self, state):
+        super().__setstate__(state)
+        self._instance = state["_instance"]
+
     def to_mongo(self, *args, **kwargs):
         data = super().to_mongo(*args, **kwargs)
 

tests/document/test_instance.py

@@ -3,6 +3,7 @@ import pickle
 import unittest
 import uuid
 import weakref
+from copy import deepcopy
 from datetime import datetime
 
 import bson
@@ -78,6 +79,14 @@ class TestDocumentInstance(MongoDBTestCase):
         else:
             assert field._instance == instance
 
+    def test_deepcopy(self):
+        """Ensure that the _instance attribute on EmbeddedDocument exists after a deepcopy"""
+
+        doc = self.Job()
+        assert doc._instance is None
+        copied = deepcopy(doc)
+        assert copied._instance is None
+
     def test_capped_collection(self):
         """Ensure that capped collections work properly."""