INTPYTHON-765 Fix crash loading EmbeddedModelField/PolymorphicEmbeddedModelField with missing fields

Author: timgraham

django_mongodb_backend/operations.py

@@ -184,6 +184,8 @@ def convert_embeddedmodelfield_value(self, value, expression, connection):
         if value is not None:
             # Apply database converters to each field of the embedded model.
             for field in expression.output_field.embedded_model._meta.fields:
+                if field.attname not in value:
+                    continue
                 field_expr = Expression(output_field=field)
                 converters = connection.ops.get_db_converters(
                     field_expr
@@ -204,6 +206,8 @@ def convert_polymorphicembeddedmodelfield_value(self, value, expression, connect
             model_class = expression.output_field._get_model_from_label(value["_label"])
             # Apply database converters to each field of the embedded model.
             for field in model_class._meta.fields:
+                if field.attname not in value:
+                    continue
                 field_expr = Expression(output_field=field)
                 converters = connection.ops.get_db_converters(
                     field_expr

docs/releases/5.2.x.rst

@@ -15,7 +15,10 @@ New features
 Bug fixes
 ---------
 
-- ...
+- Fixed a ``KeyError`` crash when loading ``EmbeddedModelField`` or
+  ``PolymorphicEmbeddedModelField`` if an embedded model field that uses a
+  converter isn't present in the data (e.g. data not written by Django, or
+  after a field was added to an existing embedded model).
 
 Deprecated features
 -------------------

tests/model_fields_/test_embedded_model.py

@@ -2,7 +2,7 @@
 from datetime import timedelta
 
 from django.core.exceptions import FieldDoesNotExist, ValidationError
-from django.db import models
+from django.db import connection, models
 from django.db.models import (
     Exists,
     ExpressionWrapper,
@@ -225,6 +225,15 @@ def test_nested(self):
         )
         self.assertCountEqual(Book.objects.filter(author__address__city="NYC"), [obj])
 
+    def test_missing_field_in_data(self):
+        """
+        Loading a model with an EmbeddedModelField that has a missing sub-field
+        (e.g. data not written by Django) that uses a database converter (in
+        this case, integer is an IntegerField) doesn't crash.
+        """
+        connection.database.model_fields__holder.update_many({}, {"$unset": {"data.integer": ""}})
+        self.assertIsNone(Holder.objects.first().data.integer)
+
 
 class ArrayFieldTests(TestCase):
     @classmethod

tests/model_fields_/test_polymorphic_embedded_model.py

@@ -2,7 +2,7 @@
 from decimal import Decimal
 
 from django.core.exceptions import FieldDoesNotExist, ValidationError
-from django.db import models
+from django.db import connection, models
 from django.test import SimpleTestCase, TestCase
 from django.test.utils import isolate_apps
 
@@ -161,6 +161,15 @@ def test_nested(self):
         with self.assertRaisesMessage(FieldDoesNotExist, msg):
             (Person.objects.filter(pet__favorite_toy__manufacturer="Maker 1"),)
 
+    def test_missing_field_in_data(self):
+        """
+        Loading a model with a PolymorphicEmbeddedModelField that has a missing
+        sub-field (e.g. data not written by Django) that uses a database
+        converter (in this case, weight is a DecimalField) doesn't crash.
+        """
+        connection.database.model_fields__person.update_many({}, {"$unset": {"pet.weight": ""}})
+        self.assertIsNone(Person.objects.first().pet.weight)
+
 
 class InvalidLookupTests(SimpleTestCase):
     def test_invalid_field(self):