From 41d1757b4ecebafa989586932366a29a6b99eefd Mon Sep 17 00:00:00 2001
From: Dmitry Rybin <dmitrika@users.noreply.github.com>
Date: Wed, 29 Jan 2020 09:12:30 +0100
Subject: [PATCH] =?UTF-8?q?fix:=209919=20Add=20warning=20when=20no=20confi?=
 =?UTF-8?q?g=20is=20exported=20from=20next.con=E2=80=A6=20(#10228)?=
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* fix: 9919 no exported config found

* fix: 9919 remove isolated test, add integration

* fix: 9919 add check for successfull compilation and fix warnin check

* Add test for development output

* fix: 9919 add error page and link to it in warning

* Update empty-configuration.md

Co-authored-by: JJ Kasper <jj@jjsweb.site>
Co-authored-by: Tim Neutkens <tim@timneutkens.nl>
---
 errors/empty-configuration.md                 | 19 ++++++++
 packages/next/next-server/server/config.ts    |  8 ++++
 test/integration/config-empty/next.config.js  |  6 +++
 test/integration/config-empty/pages/index.js  |  1 +
 .../config-empty/test/index.test.js           | 44 +++++++++++++++++++
 5 files changed, 78 insertions(+)
 create mode 100644 errors/empty-configuration.md
 create mode 100644 test/integration/config-empty/next.config.js
 create mode 100644 test/integration/config-empty/pages/index.js
 create mode 100644 test/integration/config-empty/test/index.test.js

diff --git a/errors/empty-configuration.md b/errors/empty-configuration.md
new file mode 100644
index 000000000000000..316f928d6d1de35
--- /dev/null
+++ b/errors/empty-configuration.md
@@ -0,0 +1,19 @@
+# Detected next.config.js, no exported configuration found
+
+#### Why This Warning Occurred
+
+There is no object exported from next.config.js or the object is empty.
+
+#### Possible Ways to Fix It
+
+Check if you correctly export configuration in `next.config.js` file:
+
+```
+module.exports = {
+  /* config options here */
+}
+```
+
+### Useful Links
+
+- [Introduction to next.config.js](https://nextjs.org/docs/api-reference/next.config.js/introduction)
diff --git a/packages/next/next-server/server/config.ts b/packages/next/next-server/server/config.ts
index 5fe42e75d34340d..eee2087ff1f03e7 100644
--- a/packages/next/next-server/server/config.ts
+++ b/packages/next/next-server/server/config.ts
@@ -229,6 +229,14 @@ export default function loadConfig(
       phase,
       userConfigModule.default || userConfigModule
     )
+
+    if (Object.keys(userConfig).length === 0) {
+      console.warn(
+        chalk.yellow.bold('Warning: ') +
+          'Detected next.config.js, no exported configuration found. https://err.sh/zeit/next.js/empty-configuration'
+      )
+    }
+
     if (userConfig.target && !targets.includes(userConfig.target)) {
       throw new Error(
         `Specified target is invalid. Provided: "${
diff --git a/test/integration/config-empty/next.config.js b/test/integration/config-empty/next.config.js
new file mode 100644
index 000000000000000..0c04cc72881a0fa
--- /dev/null
+++ b/test/integration/config-empty/next.config.js
@@ -0,0 +1,6 @@
+/* eslint-disable */
+{
+  experimental: {
+    basePath: '/docs'
+  }
+}
diff --git a/test/integration/config-empty/pages/index.js b/test/integration/config-empty/pages/index.js
new file mode 100644
index 000000000000000..02d90896bf336a9
--- /dev/null
+++ b/test/integration/config-empty/pages/index.js
@@ -0,0 +1 @@
+export default () => <div>Hello World</div>
diff --git a/test/integration/config-empty/test/index.test.js b/test/integration/config-empty/test/index.test.js
new file mode 100644
index 000000000000000..f0f3eb5ed11a050
--- /dev/null
+++ b/test/integration/config-empty/test/index.test.js
@@ -0,0 +1,44 @@
+/* eslint-env jest */
+/* global jasmine */
+import { join } from 'path'
+import {
+  nextBuild,
+  launchApp,
+  findPort,
+  killApp,
+  waitFor,
+} from 'next-test-utils'
+
+jasmine.DEFAULT_TIMEOUT_INTERVAL = 1000 * 60 * 2
+
+const appDir = join(__dirname, '..')
+
+describe('Empty configuration', () => {
+  it('should show relevant warning and compile successfully for next build', async () => {
+    const { stderr, stdout } = await nextBuild(appDir, [], {
+      stderr: true,
+      stdout: true,
+    })
+    expect(stdout).toMatch(/Compiled successfully./)
+    expect(stderr).toMatch(
+      /Warning: Detected next.config.js, no exported configuration found. https:\/\/err.sh\/zeit\/next.js\/empty-configuration/
+    )
+  })
+
+  it('should show relevant warning and compile successfully for next dev', async () => {
+    let stderr = ''
+
+    const appPort = await findPort()
+    const app = await launchApp(appDir, appPort, {
+      onStderr(msg) {
+        stderr += msg || ''
+      },
+    })
+    await waitFor(1000)
+    await killApp(app)
+
+    expect(stderr).toMatch(
+      /Warning: Detected next.config.js, no exported configuration found. https:\/\/err.sh\/zeit\/next.js\/empty-configuration/
+    )
+  })
+})