From 557d75eabad7cd37cc7630e0be75fb256b212d73 Mon Sep 17 00:00:00 2001
From: Vincent Gao <gaobing1230@gmail.com>
Date: Sat, 27 Jun 2026 10:56:50 +0200
Subject: [PATCH] Handle custom field validation errors

---
 rest_framework_friendly_errors/mixins.py |  4 ++--
 tests/test_serializers.py                | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/rest_framework_friendly_errors/mixins.py b/rest_framework_friendly_errors/mixins.py
index c535600..6139517 100644
--- a/rest_framework_friendly_errors/mixins.py
+++ b/rest_framework_friendly_errors/mixins.py
@@ -165,8 +165,8 @@ def get_field_error_entry(self, error, field):
                         'message': error}
             # Here we know that error was raised by custom validate method
             # in serializer
-            validator = getattr(self, "validate_%s" % field.field_name)
-            if self._run_validator(validator, field, error):
+            validator = getattr(self, "validate_%s" % field.field_name, None)
+            if validator and self._run_validator(validator, field, error):
                 name = validator.__name__
                 code = self.FIELD_VALIDATION_ERRORS.get(name) or settings.FRIENDLY_VALIDATOR_ERRORS.get(name)
                 return {'code': code, 'field': field.field_name,
diff --git a/tests/test_serializers.py b/tests/test_serializers.py
index c031eff..7a70918 100644
--- a/tests/test_serializers.py
+++ b/tests/test_serializers.py
@@ -13,6 +13,19 @@ class SimpleSerializerClass(FriendlyErrorMessagesMixin, serializers.Serializer):
     boolean_field = serializers.BooleanField(default=True)
 
 
+class CustomField(serializers.Field):
+
+    def to_internal_value(self, data):
+        raise serializers.ValidationError('Custom field error')
+
+    def to_representation(self, value):
+        return value
+
+
+class CustomFieldSerializer(FriendlyErrorMessagesMixin, serializers.Serializer):
+    custom = CustomField()
+
+
 class SanityTestCase(BaseTestCase):
 
     def test_serializer_valid(self):
@@ -151,6 +164,12 @@ def test_custom_field_validation_using_validators(self):
         self.assertEqual(s.errors['errors'][0]['field'], 'title')
         self.assertEqual(s.errors['errors'][0]['code'], 5001)
 
+    def test_custom_field_validation_error_without_validate_method(self):
+        s = run_is_valid(CustomFieldSerializer, data={'custom': 'invalid'})
+        self.assertEqual(s.errors['errors'][0]['field'], 'custom')
+        self.assertEqual(s.errors['errors'][0]['message'],
+                         'Custom field error')
+
     def test_field_dependency_validation(self):
         self.data_set['title'] = 'A Python'
         self.data_set['language'] = 'c++'