Introduce DjangoModelType

Author: wencakisa

styleguide_example/common/services.py

@@ -1,21 +1,22 @@
 from typing import List, Dict, Any, Tuple
 
+from styleguide_example.common.types import DjangoModelType
+
 
-# TODO: Decide typing for the `instance` argument
 def model_update(
     *,
-    instance: Any,
+    instance: DjangoModelType,
     fields: List[str],
     data: Dict[str, Any]
-) -> Tuple[Any, bool]:
+) -> Tuple[DjangoModelType, bool]:
     """
     Generic update service meant to be reused in local update services
 
     For example:
 
-    def user_update(*, user: User, **data) -> User:
+    def user_update(*, user: User, data) -> User:
         fields = ['first_name', 'last_name']
-        user = model_update(instance=user, fields=fields, data=data)
+        user, has_updated = model_update(instance=user, fields=fields, data=data)
 
         // Do other actions with the user here
 
@@ -27,9 +28,6 @@ def user_update(*, user: User, **data) -> User:
     """
     has_updated = False
 
-    if instance is None:
-        return instance, has_updated
-
     for field in fields:
         # Skip if a field is not present in the actual data
         if field not in data:

styleguide_example/common/tests/services/test_model_update.py

@@ -12,23 +12,6 @@ def setUp(self):
             field_c=None
         )
 
-    def test_model_update_does_not_update_if_instance_is_none(self):
-        updated_instance, has_updated = model_update(
-            instance=self.instance,
-            fields=[],
-            data={}
-        )
-
-        self.assertEqual(updated_instance, self.instance)
-        self.assertFalse(has_updated)
-
-        self.assertIsNone(updated_instance.field_a)
-        self.assertIsNone(updated_instance.field_b)
-        self.assertIsNone(updated_instance.field_c)
-
-        self.instance.full_clean.assert_not_called()
-        self.instance.save.assert_not_called()
-
     def test_model_update_does_not_update_if_none_of_the_fields_are_in_the_data(self):
         update_fields = ['non_existing_field']
         data = {'field_a': 'value_a'}

styleguide_example/common/types.py

@@ -0,0 +1,7 @@
+from typing import TypeVar
+
+from django.db import models
+
+# Generic type for a Django model
+# Reference: https://mypy.readthedocs.io/en/stable/kinds_of_types.html#the-type-of-class-objects
+DjangoModelType = TypeVar('DjangoModelType', bound=models.Model)

styleguide_example/users/services.py

@@ -25,7 +25,7 @@ def user_create(
 
 
 @transaction.atomic
-def user_update(*, user: BaseUser, **data) -> BaseUser:
+def user_update(*, user: BaseUser, data) -> BaseUser:
     non_side_effect_fields = ['first_name', 'last_name']
 
     user, has_updated = model_update(