Modified serializers.ChoiceField behavior convert display_name --> key

during deserialization and `key` --> `display_name` during serialization.

Perhaps I misunderstand the intended behavior of `fields.ChoiceField`, but I
noticed recently that the although every `ChoiceField` instance stores the full
list of choices with which it is initialized (a list of pairs of `key` and
`display_name`), I couldn't figure out when it ever uses a choice's
`display_name`. As a result, I found myself manually converting user input
values, which matched choice `display_name`s, to the underlying data values that
match the choice `key`s.

This commit modifies the behavior of `ChoiceField` instances so that they
automatically deserialize user input into the corresponding underlying data
value and do the reverse for serialization.

rest_framework/fields.py

@@ -130,7 +130,7 @@ def to_choices_dict(choices):
     """
     Convert choices into key/value dicts.
 
-    to_choices_dict([1]) -> {1: 1}
+    to_choices_dict([1]) -> {1: '1'}
     to_choices_dict([(1, '1st'), (2, '2nd')]) -> {1: '1st', 2: '2nd'}
     to_choices_dict([('Group', ((1, '1st'), 2))]) -> {'Group': {1: '1st', 2: '2'}}
     """
@@ -142,7 +142,7 @@ def to_choices_dict(choices):
     for choice in choices:
         if not isinstance(choice, (list, tuple)):
             # single choice
-            ret[choice] = choice
+            ret[choice] = str(choice)
         else:
             key, value = choice
             if isinstance(value, (list, tuple)):
@@ -150,7 +150,7 @@ def to_choices_dict(choices):
                 ret[key] = to_choices_dict(value)
             else:
                 # paired choice (key, display value)
-                ret[key] = value
+                ret[key] = str(value)
     return ret
 
 
@@ -1421,7 +1421,7 @@ class ChoiceField(Field):
     def to_representation(self, value):
         if value in ('', None):
             return value
-        return self.choice_strings_to_values.get(str(value), value)
+        return self._choices.get(value, str(value))
 
     def iter_options(self):
         """
@@ -1440,11 +1440,15 @@ class ChoiceField(Field):
         self.grouped_choices = to_choices_dict(choices)
         self._choices = flatten_choices_dict(self.grouped_choices)
 
-        # Map the string representation of choices to the underlying value.
-        # Allows us to deal with eg. integer choices while supporting either
-        # integer or string input, but still get the correct datatype out.
+        # `self._choices` is a dictionary that maps the data value of a
+        # particular choice to its display representation. Here, we want to
+        # reverse that dictionary so that when a user supplies a choice's
+        # display value as input, we can look up the underlying data value to
+        # which we should deserialize it. All of the values in the `OrderedDict`
+        # returned by `to_choices_dict` should be strings, so `display` should
+        # always be a string.
         self.choice_strings_to_values = {
-            str(key): key for key in self.choices
+            display_name: key for key, display_name in self.choices.items()
         }
 
     choices = property(_get_choices, _set_choices)

tests/test_fields.py

@@ -953,12 +953,13 @@ class TestFilePathField(FieldValues):
     """
 
     valid_inputs = {
-        __file__: __file__,
+        os.path.basename(__file__): os.path.abspath(__file__),
     }
     invalid_inputs = {
         'wrong_path': ['"wrong_path" is not a valid path choice.']
     }
     outputs = {
+        os.path.abspath(__file__): os.path.basename(__file__),
     }
     field = serializers.FilePathField(
         path=os.path.abspath(os.path.dirname(__file__))
@@ -1559,15 +1560,15 @@ class TestChoiceField(FieldValues):
     Valid and invalid values for `ChoiceField`.
     """
     valid_inputs = {
-        'poor': 'poor',
-        'medium': 'medium',
-        'good': 'good',
+        'Poor quality': 'poor',
+        'Medium quality': 'medium',
+        'Good quality': 'good',
     }
     invalid_inputs = {
         'amazing': ['"amazing" is not a valid choice.']
     }
     outputs = {
-        'good': 'good',
+        'good': 'Good quality',
         '': '',
         'amazing': 'amazing',
     }
@@ -1658,16 +1659,16 @@ class TestChoiceFieldWithType(FieldValues):
     instead of a char type.
     """
     valid_inputs = {
-        '1': 1,
-        3: 3,
+        'Poor quality': 1,
+        'Good quality': 3,
     }
     invalid_inputs = {
         5: ['"5" is not a valid choice.'],
         'abc': ['"abc" is not a valid choice.']
     }
     outputs = {
-        '1': 1,
-        1: 1
+        '1': '1',
+        1: 'Poor quality',
     }
     field = serializers.ChoiceField(
         choices=[
@@ -1703,15 +1704,15 @@ class TestChoiceFieldWithGroupedChoices(FieldValues):
     choices, rather than a list of pairs of (`value`, `description`).
     """
     valid_inputs = {
-        'poor': 'poor',
-        'medium': 'medium',
-        'good': 'good',
+        'Poor quality': 'poor',
+        'Medium quality': 'medium',
+        'Good quality': 'good',
     }
     invalid_inputs = {
         'awful': ['"awful" is not a valid choice.']
     }
     outputs = {
-        'good': 'good'
+        'good': 'Good quality'
     }
     field = serializers.ChoiceField(
         choices=[
@@ -1733,15 +1734,15 @@ class TestChoiceFieldWithMixedChoices(FieldValues):
     grouped.
     """
     valid_inputs = {
-        'poor': 'poor',
+        'Poor quality': 'poor',
         'medium': 'medium',
-        'good': 'good',
+        'Good quality': 'good',
     }
     invalid_inputs = {
         'awful': ['"awful" is not a valid choice.']
     }
     outputs = {
-        'good': 'good'
+        'good': 'Good quality'
     }
     field = serializers.ChoiceField(
         choices=[
@@ -1763,12 +1764,12 @@ class TestMultipleChoiceField(FieldValues):
     """
     valid_inputs = {
         (): set(),
-        ('aircon',): {'aircon'},
-        ('aircon', 'manual'): {'aircon', 'manual'},
+        ('AirCon',): {'aircon'},
+        ('AirCon', 'Manual drive'): {'aircon', 'manual'},
     }
     invalid_inputs = {
         'abc': ['Expected a list of items but got type "str".'],
-        ('aircon', 'incorrect'): ['"incorrect" is not a valid choice.']
+        ('AirCon', 'incorrect'): ['"incorrect" is not a valid choice.']
     }
     outputs = [
         (['aircon', 'manual', 'incorrect'], {'aircon', 'manual', 'incorrect'})

tests/test_model_serializer.py

@@ -107,7 +107,7 @@ class Issue3674ChildModel(models.Model):
 class UniqueChoiceModel(models.Model):
     CHOICES = (
         ('choice1', 'choice 1'),
-        ('choice2', 'choice 1'),
+        ('choice2', 'choice 2'),
     )
 
     name = models.CharField(max_length=254, unique=True, choices=CHOICES)
@@ -1196,7 +1196,7 @@ class Test5004UniqueChoiceField(TestCase):
                 fields = '__all__'
 
         UniqueChoiceModel.objects.create(name='choice1')
-        serializer = TestUniqueChoiceSerializer(data={'name': 'choice1'})
+        serializer = TestUniqueChoiceSerializer(data={'name': 'choice 1'})
         assert not serializer.is_valid()
         assert serializer.errors == {'name': ['unique choice model with this name already exists.']}
 

tests/test_validation.py

@@ -196,7 +196,7 @@ class TestChoiceFieldChoicesValidate(TestCase):
         Make sure a value for choices works as expected.
         """
         f = serializers.ChoiceField(choices=self.CHOICES)
-        value = self.CHOICES[0][0]
+        value = self.CHOICES[0][1]
         try:
             f.to_internal_value(value)
         except serializers.ValidationError:
@@ -218,7 +218,7 @@ class TestChoiceFieldChoicesValidate(TestCase):
         Make sure a nested value for choices works as expected.
         """
         f = serializers.ChoiceField(choices=self.CHOICES_NESTED)
-        value = self.CHOICES_NESTED[0][1][0][0]
+        value = self.CHOICES_NESTED[0][1][0][1]
         try:
             f.to_internal_value(value)
         except serializers.ValidationError: