Apply to_representation on choices

Fixes #340

src/drf_yasg/inspectors/field.py

@@ -13,7 +13,9 @@ from rest_framework.settings import api_settings as rest_framework_settings
 
 from .. import openapi
 from ..errors import SwaggerGenerationError
-from ..utils import decimal_as_float, filter_none, get_serializer_class, get_serializer_ref_name
+from ..utils import (
+    decimal_as_float, field_value_to_representation, filter_none, get_serializer_class, get_serializer_ref_name
+)
 from .base import FieldInspector, NotHandled, SerializerInspector, call_view_method
 
 try:
@@ -635,7 +637,14 @@ class ChoiceFieldInspector(FieldInspector):
 
         if isinstance(field, serializers.ChoiceField):
             enum_type = openapi.TYPE_STRING
-            enum_values = list(field.choices.keys())
+            enum_values = []
+            for choice in field.choices.keys():
+                if isinstance(field, serializers.MultipleChoiceField):
+                    choice = field_value_to_representation(field, [choice])[0]
+                else:
+                    choice = field_value_to_representation(field, choice)
+
+                enum_values.append(choice)
 
             # for ModelSerializer, try to infer the type from the associated model field
             serializer = get_parent_serializer(field)

src/drf_yasg/utils.py

@@ -2,6 +2,7 @@ import inspect
 import logging
 import sys
 from collections import OrderedDict
+from decimal import Decimal
 
 from django.db import models
 from django.utils.encoding import force_text
@@ -441,6 +442,25 @@ def force_real_str(s, encoding='utf-8', strings_only=False, errors='strict'):
     return s
 
 
+def field_value_to_representation(field, value):
+    """Convert a python value related to a field (default, choices, etc.) into its OpenAPI-compatible representation.
+
+    :param serializers.Field field: field associated with the value
+    :param obj value: value
+    :return: the converted value
+    """
+    value = field.to_representation(value)
+    if isinstance(value, Decimal):
+        if decimal_as_float(field):
+            value = float(value)
+        else:
+            value = str(value)
+
+    # JSON roundtrip ensures that the value is valid JSON;
+    # for example, sets and tuples get transformed into lists
+    return json.loads(json.dumps(value, cls=encoders.JSONEncoder))
+
+
 def get_field_default(field):
     """
     Get the default value for a field, converted to a JSON-compatible value while properly handling callables.
@@ -462,12 +482,7 @@ def get_field_default(field):
 
         if default is not serializers.empty and default is not None:
             try:
-                default = field.to_representation(default)
+                default = field_value_to_representation(field, default)
-                # JSON roundtrip ensures that the value is valid JSON;
-                # for example, sets and tuples get transformed into lists
-                default = json.loads(json.dumps(default, cls=encoders.JSONEncoder))
-                if decimal_as_float(field):
-                    default = float(default)
             except Exception:  # pragma: no cover
                 logger.warning("'default' on schema for %s will not be set because "
                                "to_representation raised an exception", field, exc_info=True)