Set cache-control public (again) (#4322)

* set cache-control public

* test for Cache-Control header

* set Cache-Control header for commons/main.js

server/index.js

@@ -161,7 +161,7 @@ export default class Server {
       '/_next/webpack/chunks/:name': async (req, res, params) => {
         // Cache aggressively in production
         if (!this.dev) {
-          res.setHeader('Cache-Control', 'max-age=31536000, immutable')
+          res.setHeader('Cache-Control', 'public, max-age=31536000, immutable')
         }
         const p = join(this.dir, this.dist, 'chunks', params.name)
         await this.serveStatic(req, res, p)
@@ -227,8 +227,12 @@ export default class Server {
       '/_next/static/:path*': async (req, res, params) => {
         // The commons folder holds commonschunk files
         // In development they don't have a hash, and shouldn't be cached by the browser.
-        if (this.dev && params.path[0] === 'commons') {
-          res.setHeader('Cache-Control', 'no-store, must-revalidate')
+        if (params.path[0] === 'commons') {
+          if (this.dev) {
+            res.setHeader('Cache-Control', 'no-store, must-revalidate')
+          } else {
+            res.setHeader('Cache-Control', 'public, max-age=31536000, immutable')
+          }
         }
         const p = join(this.dir, this.dist, 'static', ...(params.path || []))
         await this.serveStatic(req, res, p)
@@ -434,7 +438,7 @@ export default class Server {
       return false
     }
 
-    res.setHeader('Cache-Control', 'max-age=31536000, immutable')
+    res.setHeader('Cache-Control', 'public, max-age=31536000, immutable')
     return true
   }
 

test/integration/production/test/index.test.js

 /* global jasmine, describe, it, expect, beforeAll, afterAll */
 
+import { readFileSync } from 'fs'
 import { join } from 'path'
 import {
   pkg,
@@ -52,6 +53,31 @@ describe('Production Usage', () => {
       expect(res2.status).toBe(304)
     })
 
+    it('should set Cache-Control header', async () => {
+      const buildId = readFileSync(join(__dirname, '../.next/BUILD_ID'), 'utf8')
+      const buildManifest = require('../.next/build-manifest.json')
+      const url = `http://localhost:${appPort}/_next/`
+
+      const resources = []
+
+      // test a regular page
+      resources.push(`${url}${buildId}/page/index.js`)
+
+      // test dynamic chunk
+      const chunkKey = Object.keys(buildManifest).find((x) => x.includes('chunks/'))
+      resources.push(url + 'webpack/' + buildManifest[chunkKey])
+
+      // test main.js
+      const mainJsKey = Object.keys(buildManifest).find((x) => x === 'main.js')
+      resources.push(url + buildManifest[mainJsKey])
+
+      const responses = await Promise.all(resources.map((resource) => fetch(resource)))
+
+      responses.forEach((res) => {
+        expect(res.headers.get('Cache-Control')).toBe('public, max-age=31536000, immutable')
+      })
+    })
+
     it('should block special pages', async () => {
       const urls = ['/_document', '/_error']
       for (const url of urls) {