From 5dbee2a2708722a4e9835ac5738991ba394954c9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bastien=20G=C3=A9rard?= <bastien.gerard@cluepoints.com>
Date: Thu, 30 Aug 2018 16:03:16 +0200
Subject: [PATCH] Ensures EmbeddedDocumentField does not accepts references to
 Document classes in its constructor

---
 mongoengine/fields.py  | 12 +++++++++--
 tests/fields/fields.py | 47 ++++++++++++++++++++++++++++++++++++++++++
 tests/utils.py         |  8 +++++--
 3 files changed, 63 insertions(+), 4 deletions(-)

diff --git a/mongoengine/fields.py b/mongoengine/fields.py
index 16f3185f..a54d3a52 100644
--- a/mongoengine/fields.py
+++ b/mongoengine/fields.py
@@ -645,9 +645,17 @@ class EmbeddedDocumentField(BaseField):
     def document_type(self):
         if isinstance(self.document_type_obj, six.string_types):
             if self.document_type_obj == RECURSIVE_REFERENCE_CONSTANT:
-                self.document_type_obj = self.owner_document
+                resolved_document_type = self.owner_document
             else:
-                self.document_type_obj = get_document(self.document_type_obj)
+                resolved_document_type = get_document(self.document_type_obj)
+
+            if not issubclass(resolved_document_type, EmbeddedDocument):
+                # Due to the late resolution of the document_type
+                # There is a chance that it won't be an EmbeddedDocument (#1661)
+                self.error('Invalid embedded document class provided to an '
+                           'EmbeddedDocumentField')
+            self.document_type_obj = resolved_document_type
+
         return self.document_type_obj
 
     def to_python(self, value):
diff --git a/tests/fields/fields.py b/tests/fields/fields.py
index 7352d242..362acec4 100644
--- a/tests/fields/fields.py
+++ b/tests/fields/fields.py
@@ -2147,6 +2147,15 @@ class FieldTest(MongoDBTestCase):
         ]))
         self.assertEqual(a.b.c.txt, 'hi')
 
+    def test_embedded_document_field_cant_reference_using_a_str_if_it_does_not_exist_yet(self):
+        raise SkipTest("Using a string reference in an EmbeddedDocumentField does not work if the class isnt registerd yet")
+
+        class MyDoc2(Document):
+            emb = EmbeddedDocumentField('MyDoc')
+
+        class MyDoc(EmbeddedDocument):
+            name = StringField()
+
     def test_embedded_document_validation(self):
         """Ensure that invalid embedded documents cannot be assigned to
         embedded document fields.
@@ -4388,6 +4397,44 @@ class EmbeddedDocumentListFieldTestCase(MongoDBTestCase):
         self.assertEqual(custom_data['a'], CustomData.c_field.custom_data['a'])
 
 
+class TestEmbeddedDocumentField(MongoDBTestCase):
+    def test___init___(self):
+        class MyDoc(EmbeddedDocument):
+            name = StringField()
+
+        field = EmbeddedDocumentField(MyDoc)
+        self.assertEqual(field.document_type_obj, MyDoc)
+
+        field2 = EmbeddedDocumentField('MyDoc')
+        self.assertEqual(field2.document_type_obj, 'MyDoc')
+
+    def test___init___throw_error_if_document_type_is_not_EmbeddedDocument(self):
+        with self.assertRaises(ValidationError):
+            EmbeddedDocumentField(dict)
+
+    def test_document_type_throw_error_if_not_EmbeddedDocument_subclass(self):
+
+        class MyDoc(Document):
+            name = StringField()
+
+        emb = EmbeddedDocumentField('MyDoc')
+        with self.assertRaises(ValidationError) as ctx:
+            emb.document_type
+        self.assertIn('Invalid embedded document class provided to an EmbeddedDocumentField', str(ctx.exception))
+
+    def test_embedded_document_field_only_allow_subclasses_of_embedded_document(self):
+        # Relates to #1661
+        class MyDoc(Document):
+            name = StringField()
+
+        with self.assertRaises(ValidationError):
+            class MyFailingDoc(Document):
+                emb = EmbeddedDocumentField(MyDoc)
+
+        with self.assertRaises(ValidationError):
+            class MyFailingdoc2(Document):
+                emb = EmbeddedDocumentField('MyDoc')
+
 class CachedReferenceFieldTest(MongoDBTestCase):
 
     def test_cached_reference_field_get_and_save(self):
diff --git a/tests/utils.py b/tests/utils.py
index 4566d864..acd318c5 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -7,12 +7,12 @@ from mongoengine.connection import get_db, get_connection
 from mongoengine.python_support import IS_PYMONGO_3
 
 
-MONGO_TEST_DB = 'mongoenginetest'
+MONGO_TEST_DB = 'mongoenginetest'   # standard name for the test database
 
 
 class MongoDBTestCase(unittest.TestCase):
     """Base class for tests that need a mongodb connection
-    db is being dropped automatically
+    It ensures that the db is clean at the beginning and dropped at the end automatically
     """
 
     @classmethod
@@ -32,6 +32,7 @@ def get_mongodb_version():
     """
     return tuple(get_connection().server_info()['versionArray'])
 
+
 def _decorated_with_ver_requirement(func, ver_tuple):
     """Return a given function decorated with the version requirement
     for a particular MongoDB version tuple.
@@ -50,18 +51,21 @@ def _decorated_with_ver_requirement(func, ver_tuple):
 
     return _inner
 
+
 def needs_mongodb_v26(func):
     """Raise a SkipTest exception if we're working with MongoDB version
     lower than v2.6.
     """
     return _decorated_with_ver_requirement(func, (2, 6))
 
+
 def needs_mongodb_v3(func):
     """Raise a SkipTest exception if we're working with MongoDB version
     lower than v3.0.
     """
     return _decorated_with_ver_requirement(func, (3, 0))
 
+
 def skip_pymongo3(f):
     """Raise a SkipTest exception if we're running a test against
     PyMongo v3.x.