Fix database converter crash when loading models with a null ArrayField value

django_mongodb_backend/operations.py

@@ -80,6 +80,8 @@ def adapt_timefield_value(self, value):
     def _get_arrayfield_converter(self, converter, *args, **kwargs):
         # Return a database converter that can be applied to a list of values.
         def convert_value(value, expression, connection):
+            if value is None:
+                return None
             return [converter(x, expression, connection) for x in value]
 
         return convert_value

docs/source/releases/5.1.x.rst

@@ -2,6 +2,14 @@
 Django MongoDB Backend 5.1.x
 ============================
 
+5.1.0 beta 4
+============
+
+*Unreleased*
+
+- Fixed crash when loading models with a null value for ``ArrayField``\s where
+  the ``base_field`` uses a database converter.
+
 5.1.0 beta 3
 ============
 

docs/source/releases/5.2.x.rst

@@ -2,6 +2,17 @@
 Django MongoDB Backend 5.2.x
 ============================
 
+5.2.0 beta 1
+============
+
+*Unreleased*
+
+Bug fixes
+---------
+
+- Fixed crash when loading models with a null value for ``ArrayField``\s where
+  the ``base_field`` uses a database converter.
+
 5.2.0 beta 0
 ============
 

tests/model_fields_/models.py

@@ -80,7 +80,12 @@ class NestedIntegerArrayModel(models.Model):
 class OtherTypesArrayModel(models.Model):
     ips = ArrayField(models.GenericIPAddressField(), default=list)
     uuids = ArrayField(models.UUIDField(), default=list)
-    decimals = ArrayField(models.DecimalField(max_digits=5, decimal_places=2), default=list)
+    decimals = ArrayField(
+        models.DecimalField(max_digits=5, decimal_places=2),
+        default=list,
+        null=True,
+        blank=True,
+    )
     tags = ArrayField(TagField(), blank=True, null=True)
     json = ArrayField(models.JSONField(default=dict), default=list)
 

tests/model_fields_/test_arrayfield.py

@@ -195,10 +195,11 @@ def test_null_from_db_value_handling(self):
         instance = OtherTypesArrayModel.objects.create(
             ips=["192.168.0.1", "::1"],
             uuids=[uuid.uuid4()],
-            decimals=[decimal.Decimal(1.25), 1.75],
+            decimals=None,
             tags=None,
         )
         instance.refresh_from_db()
+        self.assertIsNone(instance.decimals)
         self.assertIsNone(instance.tags)
         self.assertEqual(instance.json, [])