Add DEFAULT_SCHEMA_CLASS setting (#5658)

* Add test for new setting

* Add DefaultSchema utility

* Add new setting to docs

Author: carltongibson

docs/api-guide/settings.md

@@ -94,6 +94,12 @@ A content negotiation class, that determines how a renderer is selected for the
 
 Default: `'rest_framework.negotiation.DefaultContentNegotiation'`
 
+#### DEFAULT_SCHEMA_CLASS
+
+A view inspector class that will be used for schema generation.
+
+Default: `'rest_framework.schemas.AutoSchema'`
+
 ---
 
 ## Generic view settings

rest_framework/schemas/__init__.py

@@ -23,7 +23,7 @@
 from rest_framework.settings import api_settings
 
 from .generators import SchemaGenerator
-from .inspectors import AutoSchema, ManualSchema  # noqa
+from .inspectors import AutoSchema, DefaultSchema, ManualSchema  # noqa
 
 
 def get_schema_view(

rest_framework/schemas/inspectors.py

@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 """
 inspectors.py   # Per-endpoint view introspection
 
@@ -456,3 +457,13 @@ def get_link(self, path, method, base_url):
         )
 
         return self._link
+
+
+class DefaultSchema(object):
+    """Allows overriding AutoSchema using DEFAULT_SCHEMA_CLASS setting"""
+    def __get__(self, instance, owner):
+        inspector_class = api_settings.DEFAULT_SCHEMA_CLASS
+        assert issubclass(inspector_class, ViewInspector), "DEFAULT_SCHEMA_CLASS must be set to a ViewInspector (usually an AutoSchema) subclass"
+        inspector = inspector_class()
+        inspector.view = instance
+        return inspector

rest_framework/settings.py

@@ -55,6 +55,9 @@
     'DEFAULT_PAGINATION_CLASS': None,
     'DEFAULT_FILTER_BACKENDS': (),
 
+    # Schema
+    'DEFAULT_SCHEMA_CLASS': 'rest_framework.schemas.AutoSchema',
+
     # Throttling
     'DEFAULT_THROTTLE_RATES': {
         'user': None,
@@ -140,6 +143,7 @@
     'DEFAULT_VERSIONING_CLASS',
     'DEFAULT_PAGINATION_CLASS',
     'DEFAULT_FILTER_BACKENDS',
+    'DEFAULT_SCHEMA_CLASS',
     'EXCEPTION_HANDLER',
     'TEST_REQUEST_RENDERER_CLASSES',
     'UNAUTHENTICATED_USER',

rest_framework/views.py

@@ -18,7 +18,7 @@
 from rest_framework import exceptions, status
 from rest_framework.request import Request
 from rest_framework.response import Response
-from rest_framework.schemas import AutoSchema
+from rest_framework.schemas import DefaultSchema
 from rest_framework.settings import api_settings
 from rest_framework.utils import formatting
 
@@ -117,7 +117,7 @@ class APIView(View):
     # Allow dependency injection of other settings to make testing easier.
     settings = api_settings
 
-    schema = AutoSchema()
+    schema = DefaultSchema()
 
     @classmethod
     def as_view(cls, **initkwargs):

tests/test_schemas.py

@@ -516,13 +516,30 @@ def test_4605_regression(self):
         assert prefix == '/'
 
 
+class CustomViewInspector(AutoSchema):
+    """A dummy AutoSchema subclass"""
+    pass
+
+
 class TestAutoSchema(TestCase):
 
     def test_apiview_schema_descriptor(self):
         view = APIView()
         assert hasattr(view, 'schema')
         assert isinstance(view.schema, AutoSchema)
 
+    def test_set_custom_inspector_class_on_view(self):
+        class CustomView(APIView):
+            schema = CustomViewInspector()
+
+        view = CustomView()
+        assert isinstance(view.schema, CustomViewInspector)
+
+    def test_set_custom_inspector_class_via_settings(self):
+        with override_settings(REST_FRAMEWORK={'DEFAULT_SCHEMA_CLASS': 'tests.test_schemas.CustomViewInspector'}):
+            view = APIView()
+            assert isinstance(view.schema, CustomViewInspector)
+
     def test_get_link_requires_instance(self):
         descriptor = APIView.schema  # Accessed from class
         with pytest.raises(AssertionError):