From e31558318e48a5734818360e9632239efdb1a762 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bastien=20G=C3=A9rard?= <bastien.gerard@cluepoints.com>
Date: Mon, 12 Nov 2018 23:12:35 +0100
Subject: [PATCH] BugFix - _cls not set in constructor #1950

---
 docs/changelog.rst            |  1 +
 mongoengine/base/document.py  |  3 +++
 tests/document/inheritance.py | 29 +++++++++++++++++++++++++----
 3 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index 47af2b1b..1e223aa1 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -5,6 +5,7 @@ Changelog
 Development
 ===========
 - (Fill this out as you fix issues and develop your features).
+- Fix `_cls` that is not set properly in Document constructor (regression) #1950
 - Remove deprecated `save()` method and used `insert_one()` #1899
 
 =================
diff --git a/mongoengine/base/document.py b/mongoengine/base/document.py
index 348ab24b..11b3a49a 100644
--- a/mongoengine/base/document.py
+++ b/mongoengine/base/document.py
@@ -91,6 +91,9 @@ class BaseDocument(object):
             value = getattr(self, key, None)
             setattr(self, key, value)
 
+        if '_cls' not in values:
+            self._cls = self._class_name
+
         # Set passed values after initialisation
         if self._dynamic:
             dynamic_data = {}
diff --git a/tests/document/inheritance.py b/tests/document/inheritance.py
index b4ba6058..32e3ed29 100644
--- a/tests/document/inheritance.py
+++ b/tests/document/inheritance.py
@@ -2,11 +2,11 @@
 import unittest
 import warnings
 
-from tests.fixtures import Base
-
-from mongoengine import Document, EmbeddedDocument, connect, ReferenceField,\
-    BooleanField, GenericReferenceField, IntField, StringField
+from mongoengine import (BooleanField, Document, EmbeddedDocument,
+                         EmbeddedDocumentField, GenericReferenceField,
+                         IntField, ReferenceField, StringField, connect)
 from mongoengine.connection import get_db
+from tests.fixtures import Base
 
 __all__ = ('InheritanceTest', )
 
@@ -23,6 +23,27 @@ class InheritanceTest(unittest.TestCase):
                 continue
             self.db.drop_collection(collection)
 
+    def test_constructor_cls(self):
+        # Ensures _cls is properly set during construction
+        # and when object gets reloaded (prevent regression of #1950)
+        class EmbedData(EmbeddedDocument):
+            data = StringField()
+            meta = {'allow_inheritance': True}
+
+        class DataDoc(Document):
+            name = StringField()
+            embed = EmbeddedDocumentField(EmbedData)
+            meta = {'allow_inheritance': True}
+
+        test_doc = DataDoc(name='test', embed=EmbedData(data='data'))
+        assert test_doc._cls == 'DataDoc'
+        assert test_doc.embed._cls == 'EmbedData'
+        test_doc.save()
+        saved_doc = DataDoc.objects.with_id(test_doc.id)
+        assert test_doc._cls == saved_doc._cls
+        assert test_doc.embed._cls == saved_doc.embed._cls
+        test_doc.delete()
+
     def test_superclasses(self):
         """Ensure that the correct list of superclasses is assembled.
         """