Loosen restrictions on resource route response types when accessed externally

.changeset/kind-hats-greet.md

@@ -0,0 +1,8 @@
+---
+"react-router": patch
+---
+
+Stop erroring on resource routes that return raw strings/objects and instead serialize them as `text/plain` or `application/json` responses
+
+- This only applies when accessed as a resource route without the `.data` extension
+- When accessed from a Single Fetch `.data` request, they will still be encoded via `turbo-stream`

integration/resource-routes-test.ts

@@ -61,7 +61,7 @@ test.describe("loader in an app", async () => {
           export default () => <div data-testid="redirect-destination">You made it!</div>
         `,
         "app/routes/defer.tsx": js`
-          export let loader = () => ({ data: 'whatever' });
+          export let loader = () => ({ data: Promise.resolve('whatever') });
         `,
         "app/routes/data[.]json.tsx": js`
           export let loader = () => Response.json({ hello: "world" });
@@ -101,6 +101,11 @@ test.describe("loader in an app", async () => {
             return { hello: 'world' };
           }
         `,
+        "app/routes/return-string.tsx": js`
+          export let loader = () => {
+            return 'hello world';
+          }
+        `,
         "app/routes/throw-object.tsx": js`
           export let loader = () => {
             throw { but: 'why' };
@@ -207,9 +212,25 @@ test.describe("loader in an app", async () => {
     expect(await res.text()).toEqual("Partial");
   });
 
-  // TODO: This test should work once we bring over the changes from
-  // https://github.com/remix-run/remix/pull/9349 to the v7 branch
-  test.skip("should handle objects returned from resource routes", async ({
+  test("should convert strings returned from resource routes to text responses", async ({
+    page,
+  }) => {
+    let app = new PlaywrightFixture(appFixture, page);
+    let res = await app.goto("/return-string");
+    expect(res.status()).toBe(200);
+    expect(await res.text()).toEqual("hello world");
+  });
+
+  test("should convert non-strings returned from resource routes to JSON responses", async ({
+    page,
+  }) => {
+    let app = new PlaywrightFixture(appFixture, page);
+    let res = await app.goto("/return-object");
+    expect(res.status()).toBe(200);
+    expect(await res.json()).toEqual({ hello: "world" });
+  });
+
+  test("should handle objects returned from resource routes", async ({
     page,
   }) => {
     let app = new PlaywrightFixture(appFixture, page);
@@ -256,10 +277,8 @@ test.describe("loader in an app", async () => {
   }) => {
     let app = new PlaywrightFixture(appFixture, page);
     let res = await app.goto("/defer");
-    expect(res.status()).toBe(500);
-    expect(await res.text()).toMatch(
-      "Error: Expected a Response to be returned from resource route handler"
-    );
+    expect(res.status()).toBe(200);
+    expect(await res.json()).toEqual({ data: {} });
   });
 });
 

packages/react-router/lib/server-runtime/server.ts

@@ -504,12 +504,15 @@ async function handleResourceRequest(
       requestContext: loadContext,
     });
 
-    invariant(
-      isResponse(response),
-      "Expected a Response to be returned from resource route handler"
-    );
+    if (isResponse(response)) {
+      return response;
+    }
 
-    return response;
+    if (typeof response === "string") {
+      return new Response(response);
+    }
+
+    return Response.json(response);
   } catch (error: unknown) {
     if (isResponse(error)) {
       // Note: Not functionally required but ensures that our response headers