fix: respond with correct headers and status code for HEAD requests (#20421)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

Author: sapphi-red

packages/vite/src/node/server/middlewares/transform.ts

@@ -120,7 +120,10 @@ export function transformMiddleware(
   return async function viteTransformMiddleware(req, res, next) {
     const environment = server.environments.client
 
-    if (req.method !== 'GET' || knownIgnoreList.has(req.url!)) {
+    if (
+      (req.method !== 'GET' && req.method !== 'HEAD') ||
+      knownIgnoreList.has(req.url!)
+    ) {
       return next()
     }
 

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

@@ -92,6 +92,10 @@ export function send(
   }
 
   res.statusCode = 200
-  res.end(content)
+  if (req.method === 'HEAD') {
+    res.end()
+  } else {
+    res.end(content)
+  }
   return
 }

playground/resolve/__tests__/resolve.spec.ts

@@ -1,8 +1,8 @@
 import fs from 'node:fs'
 import path from 'node:path'
 import { fileURLToPath } from 'node:url'
-import { expect, test } from 'vitest'
-import { isBuild, isWindows, page, testDir, viteTestUrl } from '~utils'
+import { describe, expect, test } from 'vitest'
+import { isBuild, isServe, isWindows, page, testDir, viteTestUrl } from '~utils'
 
 test('bom import', async () => {
   expect(await page.textContent('.utf8-bom')).toMatch('[success]')
@@ -263,3 +263,26 @@ test.runIf(isBuild)('sideEffects field glob pattern is respected', async () => {
   )
   expect(sideEffectValues).toStrictEqual(['success'])
 })
+
+describe.runIf(isServe)('HEAD request handling', () => {
+  test('HEAD request to JS file returns correct Content-Type', async () => {
+    const response = await fetch(new URL('/absolute.js', viteTestUrl), {
+      method: 'HEAD',
+    })
+    expect(response.headers.get('content-type')).toBe('text/javascript')
+    expect(response.status).toBe(200)
+    const text = await response.text()
+    expect(text).toBe('')
+  })
+
+  test('HEAD request to CSS file returns correct Content-Type', async () => {
+    const response = await fetch(new URL('/style.css', viteTestUrl), {
+      method: 'HEAD',
+      headers: {
+        Accept: 'text/css',
+      },
+    })
+    expect(response.headers.get('content-type')).toBe('text/css')
+    expect(response.status).toBe(200)
+  })
+})

playground/resolve/style.css

@@ -0,0 +1,5 @@
+/* Simple CSS for HEAD request testing */
+body {
+  margin: 0;
+  padding: 0;
+}