feat: Add an option to turn off the SPA behavior

Fixes vitejs#5720

packages/playground/nospa/__tests__/nospa.spec.ts

@@ -0,0 +1,24 @@
+// note: tests should retrieve the element at the beginning of test and reuse it
+// in later assertions to ensure CSS HMR doesn't reload the page
+
+const assertNotIndexHtml = async (path: string) => {
+  await page.goto(viteTestUrl + path)
+  const html = await page.innerHTML('body')
+  expect(html).not.toContain(
+    `This file should only ever be served as /index.html`
+  )
+}
+test('/index.html is served', async () => {
+  await page.goto(viteTestUrl + '/index.html')
+  const html = await page.innerHTML('body')
+  expect(html).toContain(`This file should only ever be served as /index.html`)
+})
+test('/ is not served', async () => {
+  await assertNotIndexHtml('/')
+})
+test('/foo/ is not served', async () => {
+  await assertNotIndexHtml('/foo/')
+})
+test('/foo/index.html is not served', async () => {
+  await assertNotIndexHtml('/foo/index.html')
+})

packages/playground/nospa/index.html

@@ -0,0 +1,3 @@
+<p>Hello</p>
+
+<p>This file should only ever be served as /index.html in serve mode</p>

packages/playground/nospa/main.js

@@ -0,0 +1 @@
+// Intentionally empty as no setup is needed

packages/playground/nospa/package.json

@@ -0,0 +1,11 @@
+{
+  "name": "nospa",
+  "private": true,
+  "version": "0.0.0",
+  "scripts": {
+    "dev": "vite",
+    "build": "vite build",
+    "debug": "node --inspect-brk ../../vite/bin/vite",
+    "preview": "vite preview"
+  }
+}

packages/playground/nospa/vite.config.js

@@ -0,0 +1,9 @@
+module.exports = {
+  build: {
+    outDir: './dist',
+    emptyOutDir: true
+  },
+  server: {
+    noSpa: true
+  }
+}

packages/vite/src/node/server/index.ts

@@ -94,6 +94,10 @@ export interface ServerOptions extends CommonServerOptions {
    * Origin for the generated asset URLs.
    */
   origin?: string
+  /**
+   * Do not serve index.html for all URLs which are not resources
+   */
+  noSpa?: boolean
 }
 
 export interface ResolvedServerOptions extends ServerOptions {
@@ -477,7 +481,7 @@ export async function createServer(
   middlewares.use(serveStaticMiddleware(root, server))
 
   // spa fallback
-  if (!middlewareMode || middlewareMode === 'html') {
+  if (!config.server.noSpa && (!middlewareMode || middlewareMode === 'html')) {
     middlewares.use(spaFallbackMiddleware(root))
   }