Use new style of `required=<bool>` not `blank` or `null`

rest_framework/serializers.py

@@ -481,17 +481,15 @@ class ModelSerializer(Serializer):
         Creates a default instance of a basic non-relational field.
         """
         kwargs = {}
+        has_default = model_field.has_default()
 
-        kwargs['blank'] = model_field.blank
-
-        if model_field.null or model_field.blank:
+        if model_field.null or model_field.blank or has_default:
             kwargs['required'] = False
 
         if isinstance(model_field, models.AutoField) or not model_field.editable:
             kwargs['read_only'] = True
 
-        if model_field.has_default():
-            kwargs['required'] = False
+        if has_default:
             kwargs['default'] = model_field.get_default()
 
         if issubclass(model_field.__class__, models.TextField):

rest_framework/tests/relations_slug.py

@@ -18,7 +18,7 @@ class ForeignKeySourceSerializer(serializers.ModelSerializer):
 
 
 class NullableForeignKeySourceSerializer(serializers.ModelSerializer):
-    target = serializers.SlugRelatedField(slug_field='name', null=True)
+    target = serializers.SlugRelatedField(slug_field='name', required=False)
 
     class Meta:
         model = NullableForeignKeySource

rest_framework/tests/serializer.py

@@ -802,7 +802,7 @@ class BlankFieldTests(TestCase):
                 model = BlankFieldModel
 
         class BlankFieldSerializer(serializers.Serializer):
-            title = serializers.CharField(blank=True)
+            title = serializers.CharField(required=False)
 
         class NotBlankFieldModelSerializer(serializers.ModelSerializer):
             class Meta: