[feature] Allow excluding fields from validation in ValidatedModelSerializer

docs/developer/other-utilities.rst

@@ -35,6 +35,22 @@ REST API Utilities
 
 A model serializer which calls the model instance ``full_clean()``.
 
+Useful to avoid duplicating model validation logic in the REST framework
+serializers.
+
+An optional ``exclude_validation`` property with a list of field names can
+be supplied to exclude specific fields from validation.
+
+Usage:
+
+.. code-block:: python
+
+    from openwisp_utils.api.serializers import ValidatedModelSerializer
+
+
+    class BaseConfigSerializer(ValidatedModelSerializer):
+        exclude_validation = ["device"]
+
 ``openwisp_utils.api.apps.ApiAppConfig``
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

openwisp_utils/api/serializers.py

@@ -1,4 +1,5 @@
 from django.core.exceptions import ImproperlyConfigured
+from django.db import models
 
 try:
     from rest_framework import serializers
@@ -10,7 +11,24 @@
 
 
 class ValidatedModelSerializer(serializers.ModelSerializer):
+    exclude_validation = None
+
     def validate(self, data):
-        instance = self.instance or self.Meta.model(**data)
-        instance.full_clean()
+        """Performs model validation on serialized data.
+
+        Allows to avoid having to duplicate model validation logic in the
+        REST API.
+        """
+        instance = self.instance
+        # if instance is empty (eg: creation)
+        # simulate for validation purposes
+        if not instance:
+            Model = self.Meta.model
+            instance = Model()
+            for key, value in data.items():
+                # avoid direct assignment for m2m (not allowed)
+                if not isinstance(Model._meta.get_field(key), models.ManyToManyField):
+                    setattr(instance, key, value)
+        # perform model validation
+        instance.full_clean(exclude=self.exclude_validation)
         return data

tests/test_project/migrations/0009_shelf_writers.py

@@ -0,0 +1,24 @@
+# Generated by Django 4.2.20 on 2025-04-30 21:58
+
+from django.conf import settings
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
+        ("test_project", "0008_book_price"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="shelf",
+            name="writers",
+            field=models.ManyToManyField(
+                blank=True,
+                related_name="writer_of",
+                to=settings.AUTH_USER_MODEL,
+                verbose_name="Writers",
+            ),
+        ),
+    ]

tests/test_project/models.py

@@ -43,6 +43,12 @@ class Shelf(TimeStampedEditableModel):
         verbose_name=_("Owner of shelf"),
         on_delete=models.CASCADE,
     )
+    writers = models.ManyToManyField(
+        "auth.User",
+        blank=True,
+        verbose_name=_("Writers"),
+        related_name="writer_of",
+    )
     created_at = models.DateTimeField(
         _("Create at"), null=True, blank=True, auto_now_add=True
     )

tests/test_project/tests/test_api.py

@@ -17,10 +17,43 @@ def test_validator_pass(self):
         result = serializer.validate(s1)
         self.assertIsInstance(result, Shelf)
 
+    def test_validator_data_dict(self):
+        s1 = self._create_shelf(name='shelf1')
+        data = s1.__dict__
+        to_delete = [
+            '_state',
+            'id',
+            'created',
+            'created_at',
+            'modified',
+        ]
+        for key in to_delete:
+            del data[key]
+        data['writers'] = [1]
+        serializer = ShelfSerializer()
+        # import ipdb; ipdb.set_trace()
+        data = serializer.validate(data)
+        # self.assertNotIn('writers', data)
+
     def test_validator_fail(self):
         with self.assertRaises(ValidationError):
             self._create_shelf(name='Intentional_Test_Fail')
 
+        s1 = self._create_shelf(name='shelf1')
+        s1.name = 'Intentional_Test_Fail'
+        serializer = ShelfSerializer(s1)
+        with self.assertRaises(ValidationError):
+            serializer.validate(s1)
+
+    def test_exclude_validation(self):
+        s1 = self._create_shelf(name='shelf1')
+        s1.books_type = 'madeup'
+        serializer = ShelfSerializer(s1)
+        with self.assertRaises(ValidationError):
+            serializer.validate(s1)
+        serializer.exclude_validation = ['books_type']
+        serializer.validate(s1)
+
     def test_rest_framework_settings_override(self):
         drf_conf = getattr(settings, 'REST_FRAMEWORK', {})
         self.assertEqual(