Ensure that ModelSerializer fields are in same order than in DRF (#1182)

* fix(ModelSerializer): preserve field order like DRF

* test(ModelSerializer): add test_get_field_names

* docs: update changelog and authors files

---------

Co-authored-by: Oliver Sauder <[email protected]>

Author: antoineauger

AUTHORS

@@ -2,6 +2,7 @@ Adam Wróbel <https://adamwrobel.com>
 Adam Ziolkowski <[email protected]>
 Alan Crosswell <[email protected]>
 Alex Seidmann <[email protected]>
+Antoine Auger <https://antoineauger.fr/en>
 Anton Shutik <[email protected]>
 Arttu Perälä <[email protected]>
 Ashley Loewen <[email protected]>

CHANGELOG.md

@@ -13,6 +13,7 @@ any parts of the framework not mentioned in the documentation should generally b
 ### Fixed
 
 * Fixed OpenAPI schema generation for `Serializer` when used inside another `Serializer` or as a child of `ListField`.
+* `ModelSerializer` fields are now returned in the same order than DRF
 
 ### Removed
 

rest_framework_json_api/serializers.py

@@ -309,11 +309,11 @@ def get_field_names(self, declared_fields, info):
         """
         meta_fields = getattr(self.Meta, "meta_fields", [])
 
-        declared = {}
-        for field_name in set(declared_fields.keys()):
-            field = declared_fields[field_name]
-            if field_name not in meta_fields:
-                declared[field_name] = field
+        declared = {
+            field_name: field
+            for field_name, field in declared_fields.items()
+            if field_name not in meta_fields
+        }
         fields = super().get_field_names(declared, info)
         return list(fields) + list(getattr(self.Meta, "meta_fields", list()))
 

tests/test_serializers.py

@@ -1,5 +1,6 @@
 import pytest
 from django.db import models
+from rest_framework.utils import model_meta
 
 from rest_framework_json_api import serializers
 from tests.models import DJAModel, ManyToManyTarget
@@ -50,3 +51,36 @@ class ReservedFieldNamesSerializer(serializers.Serializer):
         "ReservedFieldNamesSerializer uses following reserved field name(s) which is "
         "not allowed: meta, results"
     )
+
+
+def test_get_field_names():
+    class MyTestModel(DJAModel):
+        verified = models.BooleanField(default=False)
+        uuid = models.UUIDField()
+
+    class AnotherSerializer(serializers.Serializer):
+        ref_id = serializers.CharField()
+        reference_string = serializers.CharField()
+
+    class MyTestModelSerializer(AnotherSerializer, serializers.ModelSerializer):
+        an_extra_field = serializers.CharField()
+
+        class Meta:
+            model = MyTestModel
+            fields = "__all__"
+            extra_kwargs = {
+                "verified": {"read_only": True},
+            }
+
+    # Same logic than in DRF get_fields() method
+    declared_fields = MyTestModelSerializer._declared_fields
+    info = model_meta.get_field_info(MyTestModel)
+
+    assert MyTestModelSerializer().get_field_names(declared_fields, info) == [
+        "id",
+        "ref_id",
+        "reference_string",
+        "an_extra_field",
+        "verified",
+        "uuid",
+    ]