fix(cells) Fix ViewSiloLimit when applied to function views (#103949)

Fix parameter handling and request attribute extraction for view
functions that have `ViewSiloLimit` applied to them.

Fixes SENTRY-5DP1

Author: markstory

src/sentry/web/frontend/base.py

@@ -22,7 +22,6 @@
 from django.utils.decorators import method_decorator
 from django.views.decorators.csrf import csrf_exempt
 from django.views.generic import View
-from rest_framework.request import Request
 
 from sentry import options
 from sentry.api.exceptions import DataSecrecyError
@@ -80,10 +79,11 @@ def handle_when_unavailable(
         current_mode: SiloMode,
         available_modes: Iterable[SiloMode],
     ) -> Callable[..., Any]:
-        def handle(obj: Any, request: Request, *args: Any, **kwargs: Any) -> HttpResponse:
+        def handle(*args: Any, **kwargs: Any) -> HttpResponse:
+            method, path = self._request_attrs(args, kwargs)
             mode_str = ", ".join(str(m) for m in available_modes)
             message = (
-                f"Received {request.method} request at {request.path!r} to server in "
+                f"Received {method} request at {path!r} to server in "
                 f"{current_mode} mode. This view is available only in: {mode_str}"
             )
             if settings.FAIL_ON_UNAVAILABLE_API_CALL:
@@ -94,6 +94,15 @@ def handle(obj: Any, request: Request, *args: Any, **kwargs: Any) -> HttpRespons
 
         return handle
 
+    def _request_attrs(self, args: Iterable[Any], kwargs: Mapping[str, Any]) -> tuple[str, str]:
+        for arg in args:
+            if isinstance(arg, HttpRequest):
+                return (arg.method or "unknown", arg.path)
+        for value in kwargs.values():
+            if isinstance(value, HttpRequest):
+                return (value.method or "unknown", value.path)
+        return ("unknown", "unknown")
+
     def __call__(self, decorated_obj: Any) -> Any:
         if isinstance(decorated_obj, type):
             if not issubclass(decorated_obj, View):

tests/sentry/web/frontend/test_base.py

@@ -0,0 +1,45 @@
+import pytest
+from rest_framework.response import Response
+
+from sentry.silo.base import SiloMode
+from sentry.testutils.cases import APITestCase
+from sentry.testutils.silo import assume_test_silo_mode
+from sentry.web.frontend.base import BaseView, ViewSiloLimit
+
+
+class ViewSiloLimitTest(APITestCase):
+    def _test_active_on(self, endpoint_mode, active_mode, expect_to_be_active):
+        @ViewSiloLimit(endpoint_mode)
+        def view_func(request):
+            pass
+
+        @ViewSiloLimit(endpoint_mode)
+        class DummyView(BaseView):
+            def get(self, request):
+                return Response("dummy-view", 200)
+
+        view_class_func = DummyView.as_view()
+        with assume_test_silo_mode(active_mode):
+            request = self.make_request(method="GET", path="/dummy/")
+            setattr(request, "subdomain", "acme")
+
+            if expect_to_be_active:
+                view_func(request)
+                view_class_func(request)
+            else:
+                with pytest.raises(ViewSiloLimit.AvailabilityError):
+                    view_func(request)
+                with pytest.raises(ViewSiloLimit.AvailabilityError):
+                    view_class_func(request)
+
+    def test_with_active_mode(self) -> None:
+        self._test_active_on(SiloMode.REGION, SiloMode.REGION, True)
+        self._test_active_on(SiloMode.CONTROL, SiloMode.CONTROL, True)
+
+    def test_with_inactive_mode(self) -> None:
+        self._test_active_on(SiloMode.REGION, SiloMode.CONTROL, False)
+        self._test_active_on(SiloMode.CONTROL, SiloMode.REGION, False)
+
+    def test_with_monolith_mode(self) -> None:
+        self._test_active_on(SiloMode.REGION, SiloMode.MONOLITH, True)
+        self._test_active_on(SiloMode.CONTROL, SiloMode.MONOLITH, True)