Fix in-place modification of swagger_auto_schema arguments (#75)

Fixes #74

docs/changelog.rst

@@ -3,6 +3,15 @@ Changelog
 #########
 
 
+*********
+**1.4.5**
+*********
+
+*Release date: Mar 05, 2018*
+
+- **FIXED:** fixed an issue with modification of ``swagger_auto_schema`` arguments in-place during introspection, which
+  would sometimes cause an incomplete Swagger document to be generated after the first pass (:issue:`74`, :pr:`75`)
+
 *********
 **1.4.4**
 *********

src/drf_yasg/generators.py

@@ -1,3 +1,4 @@
+import copy
 import logging
 import re
 from collections import OrderedDict, defaultdict
@@ -388,7 +389,7 @@ def get_overrides(self, view, method):
         if method in overrides:
             overrides = overrides[method]
 
-        return overrides
+        return copy.deepcopy(overrides)
 
     def get_path_parameters(self, path, view_cls):
         """Return a list of Parameter instances corresponding to any templated path variables.

src/drf_yasg/utils.py

@@ -11,10 +11,15 @@
 
 logger = logging.getLogger(__name__)
 
-#: used to forcibly remove the body of a request via :func:`.swagger_auto_schema`
-no_body = object()
 
-unset = object()
+class no_body(object):
+    """Used as a sentinel value to forcibly remove the body of a request via :func:`.swagger_auto_schema`."""
+    pass
+
+
+class unset(object):
+    """Used as a sentinel value for function parameters not set by the caller where ``None`` would be a valid value."""
+    pass
 
 
 def swagger_auto_schema(method=None, methods=None, auto_schema=unset, request_body=None, query_serializer=None,
@@ -33,7 +38,7 @@ def swagger_auto_schema(method=None, methods=None, auto_schema=unset, request_bo
     :param .inspectors.SwaggerAutoSchema auto_schema: custom class to use for generating the Operation object;
         this overrides both the class-level ``swagger_schema`` attribute and the ``DEFAULT_AUTO_SCHEMA_CLASS``
         setting, and can be set to ``None`` to prevent this operation from being generated
-    :param .Schema,.SchemaRef,.Serializer request_body: custom request body, or :data:`.no_body`. The value given here
+    :param .Schema,.SchemaRef,.Serializer request_body: custom request body, or :class:`.no_body`. The value given here
         will be used as the ``schema`` property of a :class:`.Parameter` with ``in: 'body'``.
 
         A Schema or SchemaRef is not valid if this request consumes form-data, because ``form`` and ``body`` parameters

tests/test_schema_generator.py

@@ -2,11 +2,14 @@
 from collections import OrderedDict
 
 import pytest
+from rest_framework import routers, serializers, viewsets
+from rest_framework.response import Response
 
 from drf_yasg import codecs, openapi
 from drf_yasg.codecs import yaml_sane_load
 from drf_yasg.errors import SwaggerGenerationError
 from drf_yasg.generators import OpenAPISchemaGenerator
+from drf_yasg.utils import swagger_auto_schema
 
 
 def test_schema_is_valid(swagger, codec_yaml):
@@ -79,3 +82,34 @@ def test_securiy_requirements(swagger_settings, mock_schema_request):
 
     swagger = generator.get_schema(mock_schema_request, public=True)
     assert swagger['security'] == []
+
+
+def test_replaced_serializer():
+    class DetailSerializer(serializers.Serializer):
+        detail = serializers.CharField()
+
+    class DetailViewSet(viewsets.ViewSet):
+        serializer_class = DetailSerializer
+
+        @swagger_auto_schema(responses={404: openapi.Response("Not found or Not accessible", DetailSerializer)})
+        def retrieve(self, request, pk=None):
+            serializer = DetailSerializer({'detail': None})
+            return Response(serializer.data)
+
+    router = routers.DefaultRouter()
+    router.register(r'details', DetailViewSet, base_name='details')
+
+    generator = OpenAPISchemaGenerator(
+        info=openapi.Info(title="Test generator", default_version="v1"),
+        version="v2",
+        url='',
+        patterns=router.urls
+    )
+
+    for _ in range(3):
+        swagger = generator.get_schema(None, True)
+        assert 'Detail' in swagger['definitions']
+        assert 'detail' in swagger['definitions']['Detail']['properties']
+        responses = swagger['paths']['/details/{id}/']['get']['responses']
+        assert '404' in responses
+        assert responses['404']['schema']['$ref'] == "#/definitions/Detail"