Add initial process.env stubbing for new env support

errors/missing-env-value.md

@@ -2,24 +2,15 @@
 
 #### Why This Error Occurred
 
-One of your pages' config requested an env value that wasn't populated.
+In one of your pages you attempted to access an environment value that is not provided in the environment.
 
-```js
-// pages/index.js
-export const config = {
-  // this value isn't provided in `.env`
-  env: ['MISSING_KEY'],
-}
-```
+When accessing environment variables on the client they must be prefixed with `NEXT_PUBLIC_` to signify they are safe to be inlined for the client.
 
-```
-// .env (notice no `MISSING_KEY` provided here)
-NOTION_KEY='...'
-```
+When accessing environment variables on the server in `getStaticProps`, `getServerSideProps`, or an API route the value must be provided in the environment at runtime.
 
 #### Possible Ways to Fix It
 
-Either remove the requested env value from the page's config, populate it in your `.env` file, or manually populate it in your environment before running `next dev` or `next build`.
+Either remove the code accessing the env value, populate it in your `.env` file, or manually populate it in your environment before running `next dev` or `next build`.
 
 ### Useful Links
 

packages/next/build/webpack-config.ts

@@ -838,6 +838,27 @@ export default async function getBaseWebpackConfig(
               'global.GENTLY': JSON.stringify(false),
             }
           : undefined),
+        // stub process.env with proxy to warn a missing value is
+        // being accessed
+        ...(config.experimental.pageEnv
+          ? {
+              'process.env':
+                process.env.NODE_ENV === 'production'
+                  ? isServer
+                    ? 'process.env'
+                    : '{}'
+                  : `
+            new Proxy(${isServer ? 'process.env' : '{}'}, {
+              get(target, prop) {
+                if (typeof target[prop] === 'undefined') {
+                  console.warn(\`An environment variable (\${prop}) that was not provided in the environment was accessed.\nSee more info here: https://err.sh/next.js/missing-env-value\`)
+                }
+                return target[prop]
+              }
+            })
+          `,
+            }
+          : {}),
       }),
       !isServer &&
         new ReactLoadablePlugin({

test/integration/process-env-stub/next.config.js

@@ -0,0 +1,5 @@
+module.exports = {
+  experimental: {
+    pageEnv: true,
+  },
+}

test/integration/process-env-stub/pages/also-not-missing.js

@@ -0,0 +1,4 @@
+export default () => {
+  console.log(process.env.I_SHOULD_BE_HERE)
+  return <p>hi there 👋</p>
+}

test/integration/process-env-stub/pages/api/hi.js

@@ -0,0 +1,4 @@
+export default (req, res) => {
+  console.log(process.env.where_is_it)
+  res.end('done')
+}

test/integration/process-env-stub/pages/missing-gsp.js

@@ -0,0 +1,12 @@
+export default () => {
+  return <p>hi there 👋</p>
+}
+
+export const getStaticProps = () => {
+  console.log(process.env.SECRET)
+  return {
+    props: {
+      hi: 'there',
+    },
+  }
+}

test/integration/process-env-stub/pages/missing-gssp.js

@@ -0,0 +1,12 @@
+export default () => {
+  return <p>hi there 👋</p>
+}
+
+export const getServerSideProps = () => {
+  console.log(process.env.SECRET)
+  return {
+    props: {
+      hi: 'there',
+    },
+  }
+}

test/integration/process-env-stub/pages/missing.js

@@ -0,0 +1,4 @@
+export default () => {
+  console.log(process.env.hi)
+  return <p>hi there 👋</p>
+}

test/integration/process-env-stub/pages/not-missing.js

@@ -0,0 +1,4 @@
+export default () => {
+  console.log(process.env.NEXT_PUBLIC_HI)
+  return <p>hi there 👋</p>
+}

test/integration/process-env-stub/test/index.test.js

@@ -0,0 +1,110 @@
+/* eslint-env jest */
+/* global jasmine */
+import {
+  findPort,
+  killApp,
+  launchApp,
+  renderViaHTTP,
+  waitFor,
+} from 'next-test-utils'
+import { join } from 'path'
+import webdriver from 'next-webdriver'
+
+jasmine.DEFAULT_TIMEOUT_INTERVAL = 1000 * 60 * 2
+const appDir = join(__dirname, '..')
+let app
+let stderr
+let appPort
+
+const buildWarning = prop =>
+  `An environment variable (${prop}) that was not provided in the environment was accessed`
+
+const checkMissing = async (pathname, prop, shouldWarn = false) => {
+  stderr = ''
+  await renderViaHTTP(appPort, pathname)
+  await waitFor(1000)
+
+  if (shouldWarn) {
+    expect(stderr).toContain(buildWarning(prop))
+  } else {
+    expect(stderr).not.toContain(buildWarning(prop))
+  }
+}
+
+const checkMissingClient = async (pathname, prop, shouldWarn = false) => {
+  const browser = await webdriver(appPort, '/404')
+  await browser.eval(`(function() {
+    window.warnLogs = []
+    var origWarn = console.warn
+
+    console.warn = function() {
+      window.warnLogs.push(arguments[0])
+      origWarn.apply(this, arguments)
+    }
+    window.next.router.push("${pathname}")
+  })()`)
+  await waitFor(2000)
+
+  const logs = await browser.eval(`window.warnLogs`)
+  const warning = buildWarning(prop)
+  const hasWarn = logs.some(log => log.includes(warning))
+
+  expect(hasWarn).toBe(shouldWarn)
+  await browser.close()
+}
+
+describe('process.env stubbing', () => {
+  beforeAll(async () => {
+    appPort = await findPort()
+    app = await launchApp(appDir, appPort, {
+      env: {
+        NEXT_PUBLIC_HI: 'hi',
+        I_SHOULD_BE_HERE: 'hello',
+      },
+      onStderr(msg) {
+        stderr += msg || ''
+      },
+    })
+  })
+  afterAll(() => killApp(app))
+
+  describe('server side', () => {
+    it('should not show missing env value when its not missing public', async () => {
+      await checkMissing('/not-missing', 'NEXT_PUBLIC_HI')
+    })
+
+    it('should not show missing env value when its not missing runtime', async () => {
+      await checkMissing('/also-not-missing', 'I_SHOULD_BE_HERE')
+    })
+
+    it('should show missing env value when its missing normal', async () => {
+      await checkMissing('/missing', 'hi', true)
+    })
+
+    it('should show missing env value when its missing GSP', async () => {
+      await checkMissing('/missing-gsp', 'SECRET', true)
+    })
+
+    it('should show missing env value when its missing GSSP', async () => {
+      await checkMissing('/missing-gssp', 'SECRET', true)
+    })
+
+    it('should show missing env value when its missing API', async () => {
+      await checkMissing('/api/hi', 'where_is_it', true)
+    })
+  })
+
+  describe('client side', () => {
+    it('should not show missing env value when its not missing public', async () => {
+      await checkMissingClient('/not-missing', 'NEXT_PUBLIC_HI')
+    })
+
+    it('should show missing env value when its missing runtime', async () => {
+      await checkMissingClient('/also-not-missing', 'I_SHOULD_BE_HERE', true)
+    })
+
+    it('should show missing env value when its missing normal', async () => {
+      await checkMissingClient('/missing', 'hi', true)
+    })
+  })
+})