fix(preview): send configured headers

docs/config/preview-options.md

@@ -75,3 +75,9 @@ Uses [`http-proxy`](https://github.com/http-party/node-http-proxy). Full options
 - **Default:** [`server.cors`](./server-options#server-cors)
 
 Configure CORS for the preview server. This is enabled by default and allows any origin. Pass an [options object](https://github.com/expressjs/cors) to fine tune the behavior or `false` to disable.
+
+## preview.headers
+
+- **Type:** `OutgoingHttpHeaders`
+
+Specify server response headers.

packages/vite/src/node/preview.ts

@@ -111,12 +111,20 @@ export async function preview(
 
   // static assets
   const distDir = path.resolve(config.root, config.build.outDir)
+  const headers = config.preview.headers
   app.use(
     previewBase,
     sirv(distDir, {
       etag: true,
       dev: true,
-      single: config.appType === 'spa'
+      single: config.appType === 'spa',
+      setHeaders(res) {
+        if (headers) {
+          for (const name in headers) {
+            res.setHeader(name, headers[name]!)
+          }
+        }
+      }
     })
   )
 

playground/fs-serve/__tests__/fs-serve.spec.ts

@@ -1,3 +1,4 @@
+import fetch from 'node-fetch'
 import { beforeAll, describe, expect, test } from 'vitest'
 import testJSON from '../safe.json'
 import { isServe, page, viteTestUrl } from '~utils'
@@ -97,3 +98,11 @@ describe.runIf(isServe)('main', () => {
     expect(await page.textContent('.unsafe-dotenv')).toBe('404')
   })
 })
+
+describe('fetch', () => {
+  // Note: this should pass in build too, but the test setup doesn't use Vite preview
+  test.runIf(isServe)('serve with configured headers', async () => {
+    const res = await fetch(viteTestUrl + '/src/')
+    expect(res.headers.get('x-served-by')).toBe('vite')
+  })
+})

playground/fs-serve/package.json

@@ -6,6 +6,6 @@
     "dev": "vite root",
     "build": "vite build root",
     "debug": "node --inspect-brk ../../packages/vite/bin/vite",
-    "preview": "vite preview"
+    "preview": "vite preview root"
   }
 }

playground/fs-serve/root/vite.config.js

@@ -18,6 +18,14 @@ module.exports = {
     },
     hmr: {
       overlay: false
+    },
+    headers: {
+      'x-served-by': 'vite'
+    }
+  },
+  preview: {
+    headers: {
+      'x-served-by': 'vite'
     }
   },
   define: {