Resolve empty HTML charfield behavior. Closes #3318.

rest_framework/fields.py

@@ -385,8 +385,10 @@ class Field(object):
                 # If the field is blank, and null is a valid value then
                 # determine if we should use null instead.
                 return '' if getattr(self, 'allow_blank', False) else None
-            elif ret == '' and self.default:
+            elif ret == '' and not self.required:
-                return empty
+                # If the field is blank, and emptyness is valid then
+                # determine if we should use emptyness instead.
+                return '' if getattr(self, 'allow_blank', False) else empty
             return ret
         return dictionary.get(self.field_name, empty)
 

tests/test_fields.py

@@ -253,7 +253,7 @@ class TestBooleanHTMLInput:
 
 
 class TestHTMLInput:
-    def test_empty_html_charfield(self):
+    def test_empty_html_charfield_with_default(self):
         class TestSerializer(serializers.Serializer):
             message = serializers.CharField(default='happy')
 
@@ -261,6 +261,22 @@ class TestHTMLInput:
         assert serializer.is_valid()
         assert serializer.validated_data == {'message': 'happy'}
 
+    def test_empty_html_charfield_without_default(self):
+        class TestSerializer(serializers.Serializer):
+            message = serializers.CharField(allow_blank=True)
+
+        serializer = TestSerializer(data=QueryDict('message='))
+        assert serializer.is_valid()
+        assert serializer.validated_data == {'message': ''}
+
+    def test_empty_html_charfield_without_default_not_required(self):
+        class TestSerializer(serializers.Serializer):
+            message = serializers.CharField(allow_blank=True, required=False)
+
+        serializer = TestSerializer(data=QueryDict('message='))
+        assert serializer.is_valid()
+        assert serializer.validated_data == {'message': ''}
+
     def test_empty_html_integerfield(self):
         class TestSerializer(serializers.Serializer):
             message = serializers.IntegerField(default=123)