Allow dependencies to use environment variables in middlewares

packages/next/build/polyfills/process.js

@@ -0,0 +1 @@
+module.exports = global.process || require('../../compiled/process')

packages/next/build/webpack-config.ts

@@ -635,7 +635,7 @@ export default async function getBaseWebpackConfig(
  os: require.resolve('next/dist/compiled/os-browserify'),
  path: require.resolve('next/dist/compiled/path-browserify'),
  punycode: require.resolve('next/dist/compiled/punycode'),
- process: require.resolve('next/dist/compiled/process'),
+ process: require.resolve('./polyfills/process'),
  // Handled in separate alias
  querystring: require.resolve('next/dist/compiled/querystring-es3'),
  // TODO: investigate ncc'ing stream-browserify

packages/next/build/webpack/plugins/middleware-plugin.ts

@@ -295,8 +295,6 @@ export default class MiddlewarePlugin {
  .tap(PLUGIN_NAME, ignore)
 
  const memberChainHandler = (_expr: any, members: string[]) => {
- if (!isMiddlewareModule()) return
-
  if (members.length >= 2 && members[0] === 'env') {
  const envName = members[1]
  const { buildInfo } = parser.state.module
@@ -305,7 +303,7 @@ export default class MiddlewarePlugin {
  }
 
  buildInfo.nextUsedEnvVars.add(envName)
- return true
+ if (isMiddlewareModule()) return true
  }
  }
 

test/production/dependencies-can-use-env-vars-in-middlewares/index.test.ts

@@ -0,0 +1,73 @@
+import { createNext } from 'e2e-utils'
+import { NextInstance } from 'test/lib/next-modes/base'
+import { renderViaHTTP } from 'next-test-utils'
+import { readJson } from 'fs-extra'
+import path from 'path'
+
+describe('dependencies can use env vars in middlewares', () => {
+ let next: NextInstance
+
+ beforeAll(() => {
+ process.env.MY_CUSTOM_PACKAGE_ENV_VAR = 'my-custom-package-env-var'
+ process.env.ENV_VAR_USED_IN_MIDDLEWARE = 'env-var-used-in-middleware'
+ })
+
+ beforeAll(async () => {
+ next = await createNext({
+ files: {
+ // A 3rd party dependency
+ 'node_modules/my-custom-package/package.json': JSON.stringify({
+ name: 'my-custom-package',
+ version: '1.0.0',
+ browser: 'index.js',
+ }),
+ 'node_modules/my-custom-package/index.js': `
+ module.exports = () => process.env.MY_CUSTOM_PACKAGE_ENV_VAR;
+ `,
+
+ // The actual middleware code
+ 'pages/api/_middleware.js': `
+ import customPackage from 'my-custom-package';
+ export default function middleware(_req) {
+ return new Response(JSON.stringify({
+ string: "a constant string",
+ hello: process.env.ENV_VAR_USED_IN_MIDDLEWARE,
+ customPackage: customPackage(),
+ }), {
+ headers: {
+ 'Content-Type': 'application/json'
+ }
+ })
+ }
+ `,
+ },
+ dependencies: {},
+ })
+ })
+ afterAll(() => next.destroy())
+
+ it('parses the env vars correctly', async () => {
+ const testDir = next.testDir
+ const manifestPath = path.join(
+ testDir,
+ '.next/server/middleware-manifest.json'
+ )
+ const manifest = await readJson(manifestPath)
+ const envVars = manifest?.middleware?.['/api']?.env
+
+ expect(envVars).toHaveLength(2)
+ expect(envVars).toContain('ENV_VAR_USED_IN_MIDDLEWARE')
+ expect(envVars).toContain('MY_CUSTOM_PACKAGE_ENV_VAR')
+ })
+
+ it('uses the environment variables', async () => {
+ const html = await renderViaHTTP(next.url, '/api')
+ expect(html).toContain(
+ JSON.stringify({
+ string: 'a constant string',
+ hello: 'env-var-used-in-middleware',
+ customPackage: 'my-custom-package-env-var',
+ })
+ )
+ })
+})