From a59112f7f96ac371dff64e313656d6e96065e970 Mon Sep 17 00:00:00 2001
From: Kael Watts-Deuchar <kaelwd@gmail.com>
Date: Sun, 30 Sep 2018 22:24:31 +1000
Subject: [PATCH 1/3] fix(mergeOptions): skip mixins and extends if child is
 already merged

fixes #8865
---
 src/core/util/options.js                     |  4 ++--
 test/unit/features/global-api/extend.spec.js | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/src/core/util/options.js b/src/core/util/options.js
index 5f0d10d3361..7f0ad2cf788 100644
--- a/src/core/util/options.js
+++ b/src/core/util/options.js
@@ -379,10 +379,10 @@ export function mergeOptions (
   normalizeInject(child, vm)
   normalizeDirectives(child)
   const extendsFrom = child.extends
-  if (extendsFrom) {
+  if (extendsFrom && !child._base) {
     parent = mergeOptions(parent, extendsFrom, vm)
   }
-  if (child.mixins) {
+  if (child.mixins && !child._base) {
     for (let i = 0, l = child.mixins.length; i < l; i++) {
       parent = mergeOptions(parent, child.mixins[i], vm)
     }
diff --git a/test/unit/features/global-api/extend.spec.js b/test/unit/features/global-api/extend.spec.js
index 4a4a73505b9..044156074a5 100644
--- a/test/unit/features/global-api/extend.spec.js
+++ b/test/unit/features/global-api/extend.spec.js
@@ -71,6 +71,25 @@ describe('Global API: extend', () => {
     expect(calls).toEqual([1, 2, 3])
   })
 
+  it('should not merge nested mixins', () => {
+    const A = Vue.extend({
+      created: () => {}
+    })
+    const B = Vue.extend({
+      mixins: [A],
+      created: () => {}
+    })
+    const C = Vue.extend({
+      extends: B,
+      created: () => {}
+    })
+    const D = Vue.extend({
+      mixins: [C],
+      created: () => {}
+    })
+    expect(D.options.created.length).toBe(4)
+  })
+
   it('should merge methods', () => {
     const A = Vue.extend({
       methods: {

From 30c5b30f382e1ec7570c0534fb9fe41f52e3a9a4 Mon Sep 17 00:00:00 2001
From: Eduardo San Martin Morote <posva@users.noreply.github.com>
Date: Sat, 20 Oct 2018 20:49:28 +1100
Subject: [PATCH 2/3] update test name

Co-Authored-By: KaelWD <kaelwd@gmail.com>
---
 test/unit/features/global-api/extend.spec.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/unit/features/global-api/extend.spec.js b/test/unit/features/global-api/extend.spec.js
index 044156074a5..f0867ac1b5a 100644
--- a/test/unit/features/global-api/extend.spec.js
+++ b/test/unit/features/global-api/extend.spec.js
@@ -71,7 +71,7 @@ describe('Global API: extend', () => {
     expect(calls).toEqual([1, 2, 3])
   })
 
-  it('should not merge nested mixins', () => {
+  it('should not merge nested mixins created with Vue.extend', () => {
     const A = Vue.extend({
       created: () => {}
     })

From 70871837ed91d1be98a360cbf24cbf6182c459c7 Mon Sep 17 00:00:00 2001
From: Evan You <yyx990803@gmail.com>
Date: Fri, 30 Nov 2018 17:49:22 -0500
Subject: [PATCH 3/3] Update options.js

---
 src/core/util/options.js | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/src/core/util/options.js b/src/core/util/options.js
index 7f0ad2cf788..2906ddd1910 100644
--- a/src/core/util/options.js
+++ b/src/core/util/options.js
@@ -378,15 +378,22 @@ export function mergeOptions (
   normalizeProps(child, vm)
   normalizeInject(child, vm)
   normalizeDirectives(child)
-  const extendsFrom = child.extends
-  if (extendsFrom && !child._base) {
-    parent = mergeOptions(parent, extendsFrom, vm)
-  }
-  if (child.mixins && !child._base) {
-    for (let i = 0, l = child.mixins.length; i < l; i++) {
-      parent = mergeOptions(parent, child.mixins[i], vm)
+  
+  // Apply extends and mixins on the child options,
+  // but only if it is a raw options object that isn't
+  // the result of another mergeOptions call.
+  // Only merged options has the _base property.
+  if (!child._base) {
+    if (child.extends) {
+      parent = mergeOptions(parent, child.extends, vm)
+    }
+    if (child.mixins) {
+      for (let i = 0, l = child.mixins.length; i < l; i++) {
+        parent = mergeOptions(parent, child.mixins[i], vm)
+      }
     }
   }
+
   const options = {}
   let key
   for (key in parent) {