From 8cf5a21752230cd1bdbbb813f04633ac674e5e55 Mon Sep 17 00:00:00 2001
From: Ivan Nikulin <ivan.nikulin@monterail.com>
Date: Mon, 21 Aug 2017 22:21:16 +0200
Subject: [PATCH] Change build.extend hook to return new webpack config

---
 lib/builder/webpack/client.config.js     | 6 +++++-
 lib/builder/webpack/server.config.js     | 6 +++++-
 test/fixtures/with-config/nuxt.config.js | 4 +++-
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/lib/builder/webpack/client.config.js b/lib/builder/webpack/client.config.js
index 125ae385fa..e18e30e6ea 100644
--- a/lib/builder/webpack/client.config.js
+++ b/lib/builder/webpack/client.config.js
@@ -220,10 +220,14 @@ export default function webpackClientConfig () {
 
   // Extend config
   if (typeof this.options.build.extend === 'function') {
-    this.options.build.extend.call(this, config, {
+    const extendedConfig = this.options.build.extend.call(this, config, {
       dev: this.options.dev,
       isClient: true
     })
+    // Only overwrite config when something is returned for backwards compatibility
+    if (extendedConfig !== undefined) {
+      config = extendedConfig
+    }
   }
 
   return config
diff --git a/lib/builder/webpack/server.config.js b/lib/builder/webpack/server.config.js
index e9169d4084..481cbde66f 100644
--- a/lib/builder/webpack/server.config.js
+++ b/lib/builder/webpack/server.config.js
@@ -74,10 +74,14 @@ export default function webpackServerConfig () {
 
   // Extend config
   if (typeof this.options.build.extend === 'function') {
-    this.options.build.extend.call(this, config, {
+    const extendedConfig = this.options.build.extend.call(this, config, {
       dev: this.options.dev,
       isServer: true
     })
+    // Only overwrite config when something is returned for backwards compatibility
+    if (extendedConfig !== undefined) {
+      config = extendedConfig
+    }
   }
 
   return config
diff --git a/test/fixtures/with-config/nuxt.config.js b/test/fixtures/with-config/nuxt.config.js
index d97d992680..adf8eac489 100644
--- a/test/fixtures/with-config/nuxt.config.js
+++ b/test/fixtures/with-config/nuxt.config.js
@@ -34,7 +34,9 @@ module.exports = {
       generateStatsFile: true
     },
     extend (config, options) {
-      config.devtool = 'nosources-source-map'
+      return Object.assign({}, config, {
+        devtool: 'nosources-source-map'
+      })
     }
   },
   css: [