fix: prerending with SPA mode enabled renders all routes (#4800)

Author: schiller-manuel

e2e/react-start/spa-mode/package.json

@@ -7,7 +7,7 @@
     "dev": "vite dev --port 3000",
     "dev:e2e": "vite dev",
     "build": "vite build && tsc --noEmit",
-    "start": "node .output/server/index.mjs",
+    "start": "npx serve .output/public",
     "test:e2e": "rm -rf port*.txt; playwright test --project=chromium"
   },
   "dependencies": {

e2e/react-start/spa-mode/vite.config.ts

@@ -13,7 +13,16 @@ export default defineConfig({
     tanstackStart({
       spa: {
         enabled: true,
+        prerender: {
+          outputPath: 'index.html',
+        },
       },
+      pages: [
+        {
+          path: '/posts/1',
+          prerender: { enabled: true, outputPath: '/posts/1/index.html' },
+        },
+      ],
     }),
   ],
 })

e2e/solid-start/spa-mode/package.json

@@ -7,7 +7,7 @@
     "dev": "vite dev --port 3000",
     "dev:e2e": "vite dev",
     "build": "vite build && tsc --noEmit",
-    "start": "node .output/server/index.mjs",
+    "start": "npx serve .output/public",
     "test:e2e": "rm -rf port*.txt; playwright test --project=chromium"
   },
   "dependencies": {

e2e/solid-start/spa-mode/vite.config.ts

@@ -13,7 +13,17 @@ export default defineConfig({
     tanstackStart({
       spa: {
         enabled: true,
+        prerender: {
+          outputPath: 'index.html',
+          crawlLinks: true,
+        },
       },
+      pages: [
+        {
+          path: '/posts/1',
+          prerender: { enabled: true, outputPath: '/posts/1/index.html' },
+        },
+      ],
     }),
   ],
 })

packages/router-core/src/router.ts

@@ -346,6 +346,11 @@ export interface RouterOptions<
    */
   isShell?: boolean
 
+  /**
+   * @default false
+   */
+  isPrerendering?: boolean
+
   /**
    * The default `ssr` a route should use if no `ssr` is provided.
    *
@@ -833,7 +838,11 @@ export class RouterCore<
   startTransition: StartTransitionFn = (fn) => fn()
 
   isShell() {
-    return this.options.isShell
+    return !!this.options.isShell
+  }
+
+  isPrerendering() {
+    return !!this.options.isPrerendering
   }
 
   update: UpdateFn<

packages/start-plugin-core/src/nitro-plugin/plugin.ts

@@ -155,7 +155,13 @@ async function buildNitroApp(
 
     options.pages.push({
       path: maskUrl.toString().replace('http://localhost', ''),
-      prerender: options.spa.prerender,
+      prerender: {
+        ...options.spa.prerender,
+        env: {
+          ...options.spa.prerender.env,
+          TSS_SPA_MODE: 'true',
+        },
+      },
       sitemap: {
         exclude: true,
       },

packages/start-plugin-core/src/nitro-plugin/prerender.ts

@@ -171,13 +171,23 @@ export async function prerender({
           // Fetch the route
           const encodedRoute = encodeURI(page.path)
 
+          const originalEnv = { ...process.env }
+
+          process.env = {
+            ...originalEnv,
+            TSS_PRERENDERING: 'true',
+            ...(prerenderOptions.env || {}),
+          }
           const res = await localFetch<Response>(
             withBase(encodedRoute, nodeNitro.options.baseURL),
             {
-              headers: { 'x-nitro-prerender': encodedRoute },
+              headers: {
+                ...prerenderOptions.headers,
+                'x-nitro-prerender': encodedRoute,
+              },
             },
           )
-
+          process.env = originalEnv
           if (!res.ok) {
             throw new Error(`Failed to fetch ${page.path}: ${res.statusText}`, {
               cause: res,

packages/start-plugin-core/src/plugin.ts

@@ -60,7 +60,7 @@ export function TanStackStartVitePluginCore(
     resolveVirtualEntriesPlugin(opts, startConfig),
     {
       name: 'tanstack-start-core:config-client',
-      async config(viteConfig) {
+      async config(viteConfig, { command }) {
         const viteAppBase = trimPathRight(viteConfig.base || '/')
         globalThis.TSS_APP_BASE = viteAppBase
 
@@ -147,7 +147,7 @@ export function TanStackStartVitePluginCore(
             ...defineReplaceEnv('TSS_SERVER_FN_BASE', startConfig.serverFns.base),
             ...defineReplaceEnv('TSS_OUTPUT_PUBLIC_DIR', nitroOutputPublicDir),
             ...defineReplaceEnv('TSS_APP_BASE', viteAppBase),
-            ...defineReplaceEnv('TSS_SPA_MODE', startConfig.spa?.enabled ? 'true' : 'false'),
+            ...(command === 'serve' ? defineReplaceEnv('TSS_SPA_MODE', startConfig.spa?.enabled ? 'true' : 'false') : {}),
           },
         }
       },

packages/start-plugin-core/src/schema.ts

@@ -196,6 +196,8 @@ const pagePrerenderOptionsSchema = z.object({
     )
     .returns(z.any())
     .optional(),
+  headers: z.record(z.string(), z.string()).optional(),
+  env: z.record(z.string(), z.string()).optional(),
 })
 
 const spaSchema = z.object({

packages/start-server-core/src/createStartHandler.ts

@@ -126,6 +126,7 @@ export function createStartHandler<TRouter extends AnyRouter>({
       router.update({
         history,
         isShell: process.env.TSS_SPA_MODE === 'true',
+        isPrerendering: process.env.TSS_PRERENDERING === 'true',
       })
 
       const response = await (async () => {