Allow invalid outputs to pass through to_representation() for ChoiceField & MultipleChoiceField

rest_framework/fields.py

@@ -1042,10 +1042,16 @@ class ChoiceField(Field):
         except KeyError:
             self.fail('invalid_choice', input=data)
 
+    def representation_value(self, value):
+        try:
+            return self.choice_strings_to_values[six.text_type(value)]
+        except KeyError:
+            return value
+
     def to_representation(self, value):
         if value in ('', None):
             return value
-        return self.choice_strings_to_values[six.text_type(value)]
+        return self.representation_value(value)
 
 
 class MultipleChoiceField(ChoiceField):
@@ -1073,7 +1079,7 @@ class MultipleChoiceField(ChoiceField):
 
     def to_representation(self, value):
         return set([
-            self.choice_strings_to_values[six.text_type(item)] for item in value
+            self.representation_value(item) for item in value
         ])
 
 

tests/test_fields.py

@@ -920,7 +920,8 @@ class TestChoiceField(FieldValues):
     }
     outputs = {
         'good': 'good',
-        '': ''
+        '': '',
+        'amazing': 'amazing',
     }
     field = serializers.ChoiceField(
         choices=[
@@ -1005,7 +1006,7 @@ class TestMultipleChoiceField(FieldValues):
         ('aircon', 'incorrect'): ['"incorrect" is not a valid choice.']
     }
     outputs = [
-        (['aircon', 'manual'], set(['aircon', 'manual']))
+        (['aircon', 'manual', 'incorrect'], set(['aircon', 'manual', 'incorrect']))
     ]
     field = serializers.MultipleChoiceField(
         choices=[