Fix for ModelSerializer ChoiceField with nonstandard args. Closes #3126.

Author: tomchristie

rest_framework/serializers.py

@@ -1033,6 +1033,19 @@ def build_standard_field(self, field_name, model_field):
             # Fields with choices get coerced into `ChoiceField`
             # instead of using their regular typed field.
             field_class = self.serializer_choice_field
+            # Some model fields may introduce kwargs that would not be valid
+            # for the choice field. We need to strip these out.
+            # Eg. models.DecimalField(max_digits=3, decimal_places=1, choices=DECIMAL_CHOICES)
+            valid_kwargs = set((
+                'read_only', 'write_only',
+                'required', 'default', 'initial', 'source',
+                'label', 'help_text', 'style',
+                'error_messages', 'validators', 'allow_null', 'allow_blank',
+                'choices'
+            ))
+            for key in list(field_kwargs.keys()):
+                if key not in valid_kwargs:
+                    field_kwargs.pop(key)
 
         if not issubclass(field_class, ModelField):
             # `model_field` is only valid for the fallback case of

tests/test_model_serializer.py

@@ -7,6 +7,8 @@
 """
 from __future__ import unicode_literals
 
+import decimal
+
 import django
 import pytest
 from django.core.exceptions import ImproperlyConfigured
@@ -70,6 +72,7 @@ def method(self):
 
 
 COLOR_CHOICES = (('red', 'Red'), ('blue', 'Blue'), ('green', 'Green'))
+DECIMAL_CHOICES = (('low', decimal.Decimal('0.1')), ('medium', decimal.Decimal('0.5')), ('high', decimal.Decimal('0.9')))
 
 
 class FieldOptionsModel(models.Model):
@@ -82,6 +85,10 @@ class FieldOptionsModel(models.Model):
     choices_field = models.CharField(max_length=100, choices=COLOR_CHOICES)
 
 
+class MappingForChoicesWithNonStandardArgs(models.Model):
+    choices_field_with_nonstandard_args = models.DecimalField(max_digits=3, decimal_places=1, choices=DECIMAL_CHOICES)
+
+
 class TestModelSerializer(TestCase):
     def test_create_method(self):
         class TestSerializer(serializers.ModelSerializer):
@@ -307,6 +314,13 @@ class Meta:
 
         ChildSerializer().fields
 
+    def test_choices_with_nonstandard_args(self):
+        class ExampleSerializer(serializers.ModelSerializer):
+            class Meta:
+                model = MappingForChoicesWithNonStandardArgs
+
+        ExampleSerializer()
+
 
 @pytest.mark.skipif(django.VERSION < (1, 8),
                     reason='DurationField is only available for django1.8+')