blank fields shall not be required

rest_framework/utils/field_mapping.py

@@ -223,9 +223,9 @@ def get_relation_kwargs(field_name, relation_info):
             # If this field is read-only, then return early.
             # No further keyword arguments are valid.
             return kwargs
-        if model_field.has_default() or model_field.null:
+        if model_field.has_default() or model_field.blank:
             kwargs['required'] = False
-        if model_field.null:
+        if model_field.blank:
             kwargs['allow_null'] = True
         if model_field.validators:
             kwargs['validators'] = model_field.validators

tests/models.py

@@ -40,6 +40,17 @@ class ManyToManySource(RESTFrameworkModel):
     targets = models.ManyToManyField(ManyToManyTarget, related_name='sources')
 
 
+class ManyToManyBlankedSource(RESTFrameworkModel):
+    """
+    Some fields can be blank without being null
+    """
+    name = models.CharField(max_length=100)
+    surname = models.CharField(max_length=100, blank=True)
+    story = models.TextField(blank=True)
+    targets = models.ManyToManyField(ManyToManyTarget, blank=True,
+                                     related_name='blank_sources')
+
+
 # ForeignKey
 class ForeignKeyTarget(RESTFrameworkModel):
     name = models.CharField(max_length=100)

tests/test_relations_pk.py

@@ -5,6 +5,7 @@ from rest_framework import serializers
 from tests.models import (
     ManyToManyTarget, ManyToManySource, ForeignKeyTarget, ForeignKeySource,
     NullableForeignKeySource, OneToOneTarget, NullableOneToOneSource,
+    ManyToManyBlankedSource,
 )
 
 
@@ -21,6 +22,12 @@ class ManyToManySourceSerializer(serializers.ModelSerializer):
         fields = ('id', 'name', 'targets')
 
 
+class ManyToManyBlankedSourceSerializer(serializers.ModelSerializer):
+    class Meta:
+        model = ManyToManyBlankedSource
+        fields = ('id', 'name', 'surname', 'story', 'targets')
+
+
 # ForeignKey
 class ForeignKeyTargetSerializer(serializers.ModelSerializer):
     class Meta:
@@ -106,6 +113,17 @@ class PKManyToManyTests(TestCase):
         ]
         self.assertEqual(serializer.data, expected)
 
+    def test_many_to_many_blanked_retrieve(self):
+        data = {'id': 1, 'name': 'source-1-updated'}
+        instance = ManyToManyBlankedSource(name='source-%d' % data['id'])
+        instance.save()
+        serializer = ManyToManyBlankedSourceSerializer(instance, data=data)
+        self.assertTrue(serializer.is_valid())
+        serializer.save()
+        # set default values
+        data.update({'targets': [], 'surname': '', 'story': ''})
+        self.assertEqual(serializer.data, data)
+
     def test_reverse_many_to_many_update(self):
         data = {'id': 1, 'name': 'target-1', 'sources': [1]}
         instance = ManyToManyTarget.objects.get(pk=1)