Implement Response.error()

Signed-off-by: James M Snell <jsnell@cloudflare.com>

Author: jasnell

src/workerd/api/cache.c++

@@ -154,6 +154,9 @@ jsg::Promise<void> Cache::put(jsg::Lock& js,
     jsg::Ref<Response> jsResponse,
     CompatibilityFlags::Reader flags) {
 
+  JSG_REQUIRE(
+      jsResponse->getType() != "error"_kj, TypeError, "Cache is unble to store an error response");
+
   // Fake kj::HttpService::Response implementation that allows us to reuse jsResponse->send() to
   // serialize the response (headers + body) in the format needed to serve as the payload of
   // our cache PUT request.

src/workerd/api/eventsource.c++

@@ -448,6 +448,11 @@ void EventSource::run(jsg::Lock& js,
     kj::Maybe<jsg::Ref<Fetcher>> fetcher) {
   notifyOpen(js);
 
+  KJ_IF_SOME(resp, response) {
+    JSG_REQUIRE(resp->getType() != "error"_kj, TypeError,
+        "Error responses are unsupported with EventSource");
+  }
+
   auto onSuccess =
       JSG_VISITABLE_LAMBDA((self = JSG_THIS, readable = readable.addRef(), withReconnection,
                                response = addRef(response), fetcher = addRef(fetcher)),

src/workerd/api/global-scope.c++

@@ -267,6 +267,9 @@ kj::Promise<DeferredProxy<void>> ServiceWorkerGlobalScope::request(kj::HttpMetho
                         canceled = kj::addRef(*canceled), &headers, span = kj::mv(span)](
                         jsg::Lock& js, jsg::Ref<Response> innerResponse) mutable
                     -> IoOwn<kj::Promise<DeferredProxy<void>>> {
+      JSG_REQUIRE(innerResponse->getType() != "error"_kj, TypeError,
+          "Return value from serve handler must not be an error response (like Response.error())");
+
       auto& context = IoContext::current();
       // Drop our fetch_handler span now that the promise has resolved.
       span = kj::none;

src/workerd/api/html-rewriter.c++

@@ -1216,6 +1216,10 @@ jsg::Ref<HTMLRewriter> HTMLRewriter::onDocument(DocumentContentHandlers&& handle
 }
 
 jsg::Ref<Response> HTMLRewriter::transform(jsg::Lock& js, jsg::Ref<Response> response) {
+
+  JSG_REQUIRE(response->getType() != "error"_kj, TypeError,
+      "HTMLRewriter cannot transform an error response");
+
   auto maybeInput = response->getBody();
 
   if (maybeInput == kj::none) {

src/workerd/api/http-standard-test.js

@@ -1,4 +1,4 @@
-import { strictEqual } from 'node:assert';
+import { strictEqual, rejects, throws } from 'node:assert';
 
 export default {
   async fetch(req) {
@@ -11,8 +11,17 @@ export default {
       });
     } else if (req.url.endsWith('/2')) {
       return new Response('ok');
+    } else if (req.url.endsWith('/error')) {
+      const resp = Response.error();
+      strictEqual(resp.type, 'error');
+      strictEqual(resp.status, 0);
+      return resp;
     }
   },
+
+  foo() {
+    return Response.error();
+  },
 };
 
 export const test = {
@@ -33,3 +42,24 @@ export const typeTest = {
     strictEqual(resp.type, 'default');
   },
 };
+
+export const error = {
+  async test(_, env) {
+    await rejects(env.SERVICE.fetch('http://example/error'), {
+      message:
+        'Return value from serve handler must not be an error ' +
+        'response (like Response.error())',
+    });
+
+    const errorResp = Response.error();
+    throws(() => new Response('', errorResp), {
+      message:
+        'Responses may only be constructed with status codes in ' +
+        'the range 200 to 599, inclusive.',
+    });
+
+    const errorRespRpc = await env.SERVICE.foo(null);
+    strictEqual(errorRespRpc.type, 'error');
+    strictEqual(errorRespRpc.ok, false);
+  },
+};

src/workerd/api/http-standard-test.wd-test

@@ -10,8 +10,8 @@ const unitTests :Workerd.Config = (
         bindings = [
           ( name = "SERVICE", service = "http-standard-test" )
         ],
-        compatibilityDate = "2023-08-01",
-        compatibilityFlags = ["nodejs_compat", "fetch_standard_url"],
+        compatibilityDate = "2025-02-01",
+        compatibilityFlags = ["nodejs_compat"],
       )
     ),
   ],

src/workerd/api/http.c++

@@ -1334,6 +1334,10 @@ Response::Response(jsg::Lock& js,
 // Defined later in this file.
 static kj::StringPtr defaultStatusText(uint statusCode);
 
+jsg::Ref<Response> Response::error(jsg::Lock& js) {
+  return jsg::alloc<Response>(js, 0, kj::String(), jsg::alloc<Headers>(), CfProperty(), kj::none);
+};
+
 jsg::Ref<Response> Response::constructor(jsg::Lock& js,
     jsg::Optional<kj::Maybe<Body::Initializer>> optionalBodyInit,
     jsg::Optional<Initializer> maybeInit) {
@@ -1732,6 +1736,15 @@ jsg::Ref<Response> Response::deserialize(jsg::Lock& js,
     const jsg::TypeHandler<kj::Maybe<jsg::Ref<ReadableStream>>>& streamHandler) {
   auto body = KJ_ASSERT_NONNULL(streamHandler.tryUnwrap(js, deserializer.readValue(js)));
   auto init = KJ_ASSERT_NONNULL(initDictHandler.tryUnwrap(js, deserializer.readValue(js)));
+
+  // If the status code is zero, then it was an error response. We cannot
+  // use the Response::constructor.
+  KJ_IF_SOME(status, init.status) {
+    if (status == 0) {
+      return Response::error(js);
+    }
+  }
+
   return Response::constructor(js, kj::mv(body), kj::mv(init));
 }
 
@@ -2388,7 +2401,7 @@ jsg::Promise<Fetcher::GetResult> Fetcher::get(
     uint status = response->getStatus();
     if (status == 404 || status == 410) {
       return js.resolvedPromise(GetResult(js.v8Ref(js.v8Null())));
-    } else if (status < 200 || status >= 300) {
+    } else if (response->getOk()) {
       // Manually construct exception so that we can incorporate method and status into the text
       // that JavaScript sees.
       // TODO(someday): Would be nice to attach the response to the JavaScript error, maybe? Or
@@ -2680,6 +2693,10 @@ static kj::StringPtr defaultStatusText(uint statusCode) {
         return "Client Error"_kj;
       } else if (statusCode >= 500 && statusCode < 600) {
         return "Server Error"_kj;
+      } else if (statusCode == 0) {
+        // Status code 0 is used exclusively with error responses
+        // created using Response.error()
+        return ""_kj;
       } else {
         KJ_UNREACHABLE;
       }

src/workerd/api/http.h

@@ -1097,13 +1097,7 @@ class Response final: public Body {
   //
   // A network error is a response whose status is always 0, status message is always the empty
   // byte sequence, header list is always empty, body is always null, and trailer is always empty.
-  static jsg::Unimplemented error() { return {}; };
-  // TODO(conform): implementation is missing; two approaches where tested:
-  //  - returning a HTTP 5xx response but that doesn't match the spec and we didn't
-  //    find it useful.
-  //  - throwing/propagating a DISCONNECTED kj::Exception to actually disconnect the
-  //    client. However, we were concerned about possible side-effects and incorrect
-  //    error reporting.
+  static jsg::Ref<Response> error(jsg::Lock& js);
 
   jsg::Ref<Response> clone(jsg::Lock& js);
 
@@ -1139,7 +1133,10 @@ class Response final: public Body {
   // determined that only the `'default'` and `'error'` properties should be implemented.
   // We currently due not implement Response.error() so "default" is the only value we
   // currently support.
-  kj::StringPtr getType() { return "default"_kj; }
+  kj::StringPtr getType() {
+    if (statusCode == 0) return "error"_kj;
+    return "default"_kj;
+  }
 
   JSG_RESOURCE_TYPE(Response, CompatibilityFlags::Reader flags) {
     JSG_INHERIT(Body);

types/generated-snapshot/2021-11-03/index.d.ts

@@ -1566,6 +1566,7 @@ declare abstract class Body {
 declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/2021-11-03/index.ts

@@ -1571,6 +1571,7 @@ export declare abstract class Body {
 export declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/2022-01-31/index.d.ts

@@ -1572,6 +1572,7 @@ declare abstract class Body {
 declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/2022-01-31/index.ts

@@ -1577,6 +1577,7 @@ export declare abstract class Body {
 export declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/2022-03-21/index.d.ts

@@ -1590,6 +1590,7 @@ declare abstract class Body {
 declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/2022-03-21/index.ts

@@ -1595,6 +1595,7 @@ export declare abstract class Body {
 export declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/2022-08-04/index.d.ts

@@ -1590,6 +1590,7 @@ declare abstract class Body {
 declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/2022-08-04/index.ts

@@ -1595,6 +1595,7 @@ export declare abstract class Body {
 export declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/2022-10-31/index.d.ts

@@ -1590,6 +1590,7 @@ declare abstract class Body {
 declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/2022-10-31/index.ts

@@ -1595,6 +1595,7 @@ export declare abstract class Body {
 export declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/2022-11-30/index.d.ts

@@ -1595,6 +1595,7 @@ declare abstract class Body {
 declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/2022-11-30/index.ts

@@ -1600,6 +1600,7 @@ export declare abstract class Body {
 export declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/2023-03-01/index.d.ts

@@ -1597,6 +1597,7 @@ declare abstract class Body {
 declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/2023-03-01/index.ts

@@ -1602,6 +1602,7 @@ export declare abstract class Body {
 export declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/2023-07-01/index.d.ts

@@ -1597,6 +1597,7 @@ declare abstract class Body {
 declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/2023-07-01/index.ts

@@ -1602,6 +1602,7 @@ export declare abstract class Body {
 export declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/experimental/index.d.ts

@@ -1607,6 +1607,7 @@ declare abstract class Body {
 declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/experimental/index.ts

@@ -1612,6 +1612,7 @@ export declare abstract class Body {
 export declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/oldest/index.d.ts

@@ -1566,6 +1566,7 @@ declare abstract class Body {
 declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };

types/generated-snapshot/oldest/index.ts

@@ -1571,6 +1571,7 @@ export declare abstract class Body {
 export declare var Response: {
   prototype: Response;
   new (body?: BodyInit | null, init?: ResponseInit): Response;
+  error(): Response;
   redirect(url: string, status?: number): Response;
   json(any: any, maybeInit?: ResponseInit | Response): Response;
 };