From f8f06411e1adf65675df711873fc4c87075f1348 Mon Sep 17 00:00:00 2001
From: Lindsay Levine <lindslev.ll@gmail.com>
Date: Wed, 18 Nov 2020 06:10:28 -0500
Subject: [PATCH] fail build if app is using NoN already

---
 index.js      | 15 +++++++++------
 test/index.js | 30 ++++++++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/index.js b/index.js
index 2ba25c3a70..2e7e37dca2 100644
--- a/index.js
+++ b/index.js
@@ -31,12 +31,15 @@ module.exports = {
       return failBuild(`** Static HTML export next.js projects do not require this plugin **`)
     }
 
-    // TO-DO: check scripts to make sure the app isn't manually running NoN
-    // For now, we'll make it clear in the README
-    // const isAlreadyUsingNextOnNetlify = Object.keys(dependencies).find((dep) => dep === 'next-on-netlify');
-    // if (isAlreadyUsingNextOnNetlify) {
-    //   return failBuild(`This plugin cannot support apps that manually use next-on-netlify. Uninstall next-on-netlify as a dependency to resolve.`);
-    // }
+    const hasNextOnNetlifyInstalled = dependencies['next-on-netlify'] !== undefined
+    const hasNextOnNetlifyPostbuildScript =
+      typeof scripts.postbuild === 'string' && scripts.postbuild.includes('next-on-netlify')
+    const isAlreadyUsingNextOnNetlify = hasNextOnNetlifyInstalled || hasNextOnNetlifyPostbuildScript
+    if (isAlreadyUsingNextOnNetlify) {
+      return failBuild(
+        `This plugin does not support sites that manually use next-on-netlify. Uninstall next-on-netlify as a dependency to resolve.`,
+      )
+    }
 
     const nextConfigPath = await findUp('next.config.js')
     if (nextConfigPath !== undefined) {
diff --git a/test/index.js b/test/index.js
index a5bccf3330..101cc3ab3d 100644
--- a/test/index.js
+++ b/test/index.js
@@ -83,6 +83,36 @@ describe('preBuild()', () => {
     ).rejects.toThrow('** Static HTML export next.js projects do not require this plugin **')
   })
 
+  test('fail build if app has next-on-netlify installed', async () => {
+    const packageJson = {
+      dependencies: { 'next-on-netlify': '123' },
+    }
+    await expect(
+      plugin.onPreBuild({
+        netlifyConfig: {},
+        packageJson,
+        utils,
+      }),
+    ).rejects.toThrow(
+      `This plugin does not support sites that manually use next-on-netlify. Uninstall next-on-netlify as a dependency to resolve.`,
+    )
+  })
+
+  test('fail build if app has next-on-netlify postbuild script', async () => {
+    const packageJson = {
+      scripts: { postbuild: 'next-on-netlify' },
+    }
+    await expect(
+      plugin.onPreBuild({
+        netlifyConfig: {},
+        packageJson,
+        utils,
+      }),
+    ).rejects.toThrow(
+      `This plugin does not support sites that manually use next-on-netlify. Uninstall next-on-netlify as a dependency to resolve.`,
+    )
+  })
+
   test('fail build if the app has no package.json', async () => {
     await expect(
       plugin.onPreBuild({