From fe578e0afe354d285cc4539e2dc57e28b8464b90 Mon Sep 17 00:00:00 2001
From: Matt Brophy <matt@brophy.org>
Date: Tue, 28 May 2024 10:54:37 -0400
Subject: [PATCH] Single Fetch: fix issues returning/throwing response stubs
 from resource routes (#9488)

---
 .changeset/smart-mirrors-flow.md        |   6 ++
 integration/single-fetch-test.ts        | 111 ++++++++++++++++++++++++
 packages/remix-server-runtime/server.ts |  16 +++-
 3 files changed, 132 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/smart-mirrors-flow.md

diff --git a/.changeset/smart-mirrors-flow.md b/.changeset/smart-mirrors-flow.md
new file mode 100644
index 00000000000..ffd88d253af
--- /dev/null
+++ b/.changeset/smart-mirrors-flow.md
@@ -0,0 +1,6 @@
+---
+"@remix-run/server-runtime": patch
+---
+
+- Fix error when returning null from a resource route in single fetch
+- Fix issues with returning or throwing a response stub from a resource route in single fetch
diff --git a/integration/single-fetch-test.ts b/integration/single-fetch-test.ts
index 75807384b80..a3aa4f0d039 100644
--- a/integration/single-fetch-test.ts
+++ b/integration/single-fetch-test.ts
@@ -1539,6 +1539,33 @@ test.describe("single-fetch", () => {
     console.warn = oldConsoleWarn;
   });
 
+  test("allows resource routes to return null using a response stub", async () => {
+    let fixture = await createFixture(
+      {
+        config: {
+          future: {
+            unstable_singleFetch: true,
+          },
+        },
+        files: {
+          ...files,
+          "app/routes/resource.tsx": js`
+            export function loader({ response }) {
+              response.status = 201;
+              response.headers.set('X-Created-Id', '1');
+              return null;
+            }
+          `,
+        },
+      },
+      ServerMode.Development
+    );
+    let res = await fixture.requestResource("/resource");
+    expect(res.status).toBe(201);
+    expect(res.headers.get("X-Created-Id")).toBe("1");
+    expect(await res.text()).toBe("");
+  });
+
   test("processes response stub onto resource routes returning raw data", async () => {
     let fixture = await createFixture(
       {
@@ -1618,6 +1645,90 @@ test.describe("single-fetch", () => {
     });
   });
 
+  test("processes returned response stub redirects", async () => {
+    let fixture = await createFixture(
+      {
+        config: {
+          future: {
+            unstable_singleFetch: true,
+          },
+        },
+        files: {
+          ...files,
+          "app/routes/resource.tsx": js`
+            import { json } from '@remix-run/node';
+
+            export function loader({ response }) {
+              response.status = 301;
+              response.headers.set('Location', '/whatever')
+              return response;
+            }
+          `,
+        },
+      },
+      ServerMode.Development
+    );
+    let res = await fixture.requestResource("/resource");
+    expect(res.status).toBe(301);
+    expect(res.headers.get("Location")).toBe("/whatever");
+  });
+
+  test("processes thrown response stub redirects", async () => {
+    let fixture = await createFixture(
+      {
+        config: {
+          future: {
+            unstable_singleFetch: true,
+          },
+        },
+        files: {
+          ...files,
+          "app/routes/resource.tsx": js`
+            import { json } from '@remix-run/node';
+
+            export function loader({ response }) {
+              response.status = 301;
+              response.headers.set('Location', '/whatever')
+              throw response;
+            }
+          `,
+        },
+      },
+      ServerMode.Development
+    );
+    let res = await fixture.requestResource("/resource");
+    expect(res.status).toBe(301);
+    expect(res.headers.get("Location")).toBe("/whatever");
+  });
+
+  test("processes response stub redirects when null is returned", async () => {
+    let fixture = await createFixture(
+      {
+        config: {
+          future: {
+            unstable_singleFetch: true,
+          },
+        },
+        files: {
+          ...files,
+          "app/routes/resource.tsx": js`
+            import { json } from '@remix-run/node';
+
+            export function loader({ response }) {
+              response.status = 301;
+              response.headers.set('Location', '/whatever')
+              return null;
+            }
+          `,
+        },
+      },
+      ServerMode.Development
+    );
+    let res = await fixture.requestResource("/resource");
+    expect(res.status).toBe(301);
+    expect(res.headers.get("Location")).toBe("/whatever");
+  });
+
   test("allows fetcher to hit resource route and return via turbo stream", async ({
     page,
   }) => {
diff --git a/packages/remix-server-runtime/server.ts b/packages/remix-server-runtime/server.ts
index 8c0a797a86a..566c515ecfc 100644
--- a/packages/remix-server-runtime/server.ts
+++ b/packages/remix-server-runtime/server.ts
@@ -591,7 +591,7 @@ async function handleResourceRequest(
         : null),
     });
 
-    if (typeof response === "object") {
+    if (typeof response === "object" && response !== null) {
       invariant(
         !(DEFERRED_SYMBOL in response),
         `You cannot return a \`defer()\` response from a Resource Route.  Did you ` +
@@ -609,6 +609,13 @@ async function handleResourceRequest(
           // @ts-expect-error
           response.headers[op](...args);
         }
+      } else if (isResponseStub(response) || response == null) {
+        // If the stub or null was returned, then there is no body so we just
+        // proxy along the status/headers to a Response
+        response = new Response(null, {
+          status: stub.status,
+          headers: stub.headers,
+        });
       } else {
         console.warn(
           resourceRouteJsonWarning(
@@ -639,6 +646,13 @@ async function handleResourceRequest(
       return error;
     }
 
+    if (isResponseStub(error)) {
+      return new Response(null, {
+        status: error.status,
+        headers: error.headers,
+      });
+    }
+
     if (isRouteErrorResponse(error)) {
       if (error) {
         handleError(error);