Enable .env support by default (#12911)

* Enable .env support by default

Given we've had tons of reports from various people that expected .env support to work even though they had dotenv installed already I think it's fine to enable it as a default:

Fixes #12728

* Remove old test

* Fix duplicate env loading

* Update docs
Co-authored-by: NJJ Kasper <jj@jjsweb.site>

docs/basic-features/environment-variables.md

@@ -47,7 +47,6 @@ npx cross-env NEXT_PUBLIC_EXAMPLE_KEY=my-value next dev
 
 - Trying to destructure `process.env` variables won't work due to the limitations of webpack's [DefinePlugin](https://webpack.js.org/plugins/define-plugin/).
 - To avoid exposing secrets, do not use the `NEXT_PUBLIC_` prefix for them. Instead, [expose the variables using `.env`](#exposing-environment-variables).
-- You cannot have `dotenv` installed in your project, as this will cause Next.js to disable the auto-loading of the environment variables. Look for and uninstall this package if your variables are showing up as `undefined`.
 
 ## Exposing Environment Variables
 

errors/env-loading-disabled.md

@@ -8,7 +8,9 @@ This is also disabled if a `package.json` isn't able to found in your project so
 
 #### Possible Ways to Fix It
 
-Remove `dotenv` from your `devDependencies` or `dependencies` and allow Next.js to load your `dotenv` files for you
+Update to the latest version of Next.js (>= v9.4.1) where this support is enabled regardless of `dotenv` being installed.
+
+Remove `dotenv` from your `devDependencies` or `dependencies` and allow Next.js to load your `dotenv` files for you.
 
 ### Useful Links
 

packages/next/lib/load-env-config.ts

 import fs from 'fs'
 import path from 'path'
 import * as log from '../build/output/log'
-import findUp from 'next/dist/compiled/find-up'
-import { execOnce } from '../next-server/lib/utils'
 import dotenvExpand from 'next/dist/compiled/dotenv-expand'
 import dotenv, { DotenvConfigOutput } from 'next/dist/compiled/dotenv'
 
 export type Env = { [key: string]: string }
 
-const packageJsonHasDep = (packageJsonPath: string, dep: string): boolean => {
-  const { dependencies, devDependencies } = require(packageJsonPath)
-  const allPackages = Object.keys({
-    ...dependencies,
-    ...devDependencies,
-  })
-
-  return allPackages.some(pkg => pkg === dep)
-}
-
 let combinedEnv: Env | undefined = undefined
 
-const envLoadingDisabledWarning = execOnce((packageFile?: string) => {
-  log.warn(
-    (packageFile
-      ? `dotenv loading was disabled due to the \`dotenv\` package being installed in: ${packageFile}`
-      : `dotenv loading was disabled due to no package.json file able to be found`) +
-      `\nSee more info here: https://err.sh/next.js/env-loading-disabled`
-  )
-})
-
 export function loadEnvConfig(dir: string, dev?: boolean): Env | false {
+  // don't reload env if we already have since this breaks escaped
+  // environment values e.g. \$ENV_FILE_KEY
   if (combinedEnv) return combinedEnv
 
-  const packageJson = findUp.sync('package.json', { cwd: dir })
-
-  // only do new env loading if dotenv isn't installed since we
-  // can't check for an experimental flag in next.config.js
-  // since we want to load the env before loading next.config.js
-  if (packageJson) {
-    // check main `package.json` first
-    if (packageJsonHasDep(packageJson, 'dotenv')) {
-      envLoadingDisabledWarning(path.relative(dir, packageJson))
-      return false
-    }
-    // check for a yarn.lock or lerna.json file in case it's a monorepo
-    const monorepoFile = findUp.sync(
-      ['yarn.lock', 'lerna.json', 'package-lock.json'],
-      { cwd: dir }
-    )
-
-    if (monorepoFile) {
-      const monorepoRoot = path.dirname(monorepoFile)
-      const monorepoPackageJson = path.join(monorepoRoot, 'package.json')
-
-      try {
-        if (packageJsonHasDep(monorepoPackageJson, 'dotenv')) {
-          envLoadingDisabledWarning(path.relative(dir, monorepoPackageJson))
-          return false
-        }
-      } catch (_) {}
-    }
-  } else {
-    // we should always have a package.json but disable in case we don't
-    envLoadingDisabledWarning()
-    return false
-  }
-
   const isTest = process.env.NODE_ENV === 'test'
   const mode = isTest ? 'test' : dev ? 'development' : 'production'
   const dotenvFiles = [

test/integration/env-config-disable/app/package.json

-{
-  "name": "env-config",
-  "devDependencies": {
-    "dotenv": "latest"
-  }
-}

test/integration/env-config-disable/app/packages/sub-app/.env/.env.development

-HELLO=world
\ No newline at end of file

test/integration/env-config-disable/app/packages/sub-app/package.json

-{
-  "name": "env-config",
-  "dependencies": {}
-}

test/integration/env-config-disable/app/packages/sub-app/pages/index.js

-export default () => 'hi'

test/integration/env-config-disable/test/index.test.js

-/* eslint-env jest */
-/* global jasmine */
-import fs from 'fs-extra'
-import { join } from 'path'
-import {
-  nextBuild,
-  findPort,
-  launchApp,
-  killApp,
-  nextStart,
-  renderViaHTTP,
-} from 'next-test-utils'
-
-jasmine.DEFAULT_TIMEOUT_INTERVAL = 1000 * 60 * 2
-
-const monorepoRoot = join(__dirname, '../app')
-const yarnLock = join(monorepoRoot, 'yarn.lock')
-const lernaConf = join(monorepoRoot, 'lerna.json')
-const appDir = join(monorepoRoot, 'packages/sub-app')
-
-let app
-let appPort
-
-const runTests = () => {
-  describe('dev mode', () => {
-    it('should start dev server without errors', async () => {
-      let stderr = ''
-      let stdout = ''
-      appPort = await findPort()
-      app = await launchApp(appDir, appPort, {
-        onStderr(msg) {
-          stderr += msg || ''
-        },
-        onStdout(msg) {
-          stdout += msg || ''
-        },
-      })
-
-      const html = await renderViaHTTP(appPort, '/')
-      await killApp(app)
-
-      expect(html).toContain('hi')
-      expect(stderr).not.toContain('Failed to load env')
-      expect(stdout).toContain(
-        'dotenv loading was disabled due to the `dotenv` package being installed in'
-      )
-    })
-  })
-
-  describe('production mode', () => {
-    it('should build app successfully', async () => {
-      const { stderr, stdout, code } = await nextBuild(appDir, [], {
-        stderr: true,
-        stdout: true,
-      })
-      expect(code).toBe(0)
-      expect((stderr || '').length).toBe(0)
-      expect(stdout).toContain(
-        'dotenv loading was disabled due to the `dotenv` package being installed in'
-      )
-    })
-
-    it('should start without error', async () => {
-      let stderr = ''
-      let stdout = ''
-      appPort = await findPort()
-      app = await nextStart(appDir, appPort, {
-        onStderr(msg) {
-          stderr += msg || ''
-        },
-        onStdout(msg) {
-          stdout += msg || ''
-        },
-      })
-
-      const html = await renderViaHTTP(appPort, '/')
-      await killApp(app)
-
-      expect(html).toContain('hi')
-      expect(stderr).not.toContain('Failed to load env')
-      expect(stdout).toContain(
-        'dotenv loading was disabled due to the `dotenv` package being installed in'
-      )
-    })
-  })
-}
-
-describe('Env support disabling', () => {
-  describe('with yarn based monorepo', () => {
-    beforeAll(() => fs.writeFile(yarnLock, 'test'))
-    afterAll(() => fs.remove(yarnLock))
-
-    runTests()
-  })
-
-  describe('with lerna based monorepo', () => {
-    beforeAll(() => fs.writeFile(lernaConf, 'test'))
-    afterAll(() => fs.remove(lernaConf))
-
-    runTests()
-  })
-})