Fix OpenAPISchema rendering for timedelta (#7641)

* Add failing test when rendering to json a schema with timedelta

* Fix JSONOpenAPIRenderer for fields with default=timedelta()

* fix isort

* fix test for python 3.5

Co-authored-by: Pierre Chiquet <pierre.chiquet@ubikey.fr>

rest_framework/renderers.py

@@ -1063,7 +1063,8 @@ class OpenAPIRenderer(BaseRenderer):
 class JSONOpenAPIRenderer(BaseRenderer):
     media_type = 'application/vnd.oai.openapi+json'
     charset = None
+    encoder_class = encoders.JSONEncoder
     format = 'openapi-json'
 
     def render(self, data, media_type=None, renderer_context=None):
-        return json.dumps(data, indent=2).encode('utf-8')
+        return json.dumps(data, cls=self.encoder_class, indent=2).encode('utf-8')

tests/schemas/test_openapi.py

@@ -11,7 +11,8 @@ from rest_framework.authtoken.views import obtain_auth_token
 from rest_framework.compat import uritemplate
 from rest_framework.parsers import JSONParser, MultiPartParser
 from rest_framework.renderers import (
-    BaseRenderer, BrowsableAPIRenderer, JSONRenderer, OpenAPIRenderer
+    BaseRenderer, BrowsableAPIRenderer, JSONOpenAPIRenderer, JSONRenderer,
+    OpenAPIRenderer
 )
 from rest_framework.request import Request
 from rest_framework.schemas.openapi import AutoSchema, SchemaGenerator
@@ -992,6 +993,19 @@ class TestGenerator(TestCase):
         assert 'openapi' in schema
         assert 'paths' in schema
 
+    def test_schema_rendering_to_json(self):
+        patterns = [
+            path('example/', views.ExampleGenericAPIView.as_view()),
+        ]
+        generator = SchemaGenerator(patterns=patterns)
+
+        request = create_request('/')
+        schema = generator.get_schema(request=request)
+        ret = JSONOpenAPIRenderer().render(schema)
+
+        assert b'"openapi": "' in ret
+        assert b'"default": "0.0"' in ret
+
     def test_schema_with_no_paths(self):
         patterns = []
         generator = SchemaGenerator(patterns=patterns)

tests/schemas/views.py

@@ -1,4 +1,5 @@
 import uuid
+from datetime import timedelta
 
 from django.core.validators import (
     DecimalValidator, MaxLengthValidator, MaxValueValidator,
@@ -59,6 +60,7 @@ class DocStringExampleDetailView(APIView):
 class ExampleSerializer(serializers.Serializer):
     date = serializers.DateField()
     datetime = serializers.DateTimeField()
+    duration = serializers.DurationField(default=timedelta())
     hstore = serializers.HStoreField()
     uuid_field = serializers.UUIDField(default=uuid.uuid4)