feat: copy .env file in standalone mode

packages/next/build/index.ts

@@ -2037,6 +2037,7 @@ export default async function build(
       for (const file of [
         ...requiredServerFiles.files,
         path.join(config.distDir, SERVER_FILES_MANIFEST),
+        '.env',
       ]) {
         const filePath = path.join(dir, file)
         await promises.copyFile(

test/production/required-server-files.test.ts

@@ -19,6 +19,7 @@ describe('should set-up next', () => {
   let appPort
   let errors = []
   let requiredFilesManifest
+  const envPath = join(__dirname, 'required-server-files/.env')
 
   beforeAll(async () => {
     // test build against environment with next support
@@ -31,6 +32,7 @@ describe('should set-up next', () => {
         'data.txt': new FileRef(
           join(__dirname, 'required-server-files/data.txt')
         ),
+        '.env': new FileRef(envPath),
       },
       nextConfig: {
         eslint: {
@@ -722,4 +724,13 @@ describe('should set-up next', () => {
     const $ = cheerio.load(html)
     expect($('#slug-page').text()).toBe('[slug] page')
   })
+
+  it('should copy and read .env file', async () => {
+    const res = await fetchViaHTTP(appPort, '/api/env')
+
+    const envVariable = await res.text()
+    const envFromFile = fs.readFileSync(envPath).toString().split('=')[1]
+
+    expect(envFromFile).toBe(envVariable)
+  })
 })

test/production/required-server-files/.env

@@ -0,0 +1 @@
+FOO=bar

test/production/required-server-files/pages/api/env.js

@@ -0,0 +1,3 @@
+export default function handler(_, res) {
+  res.send(process.env.FOO)
+}