From 836c009d08e62af216956a8bd5288c7c1d92fbe6 Mon Sep 17 00:00:00 2001
From: Troy Morehouse <troymore@nbnet.nb.ca>
Date: Tue, 5 Mar 2019 03:37:38 -0400
Subject: [PATCH 01/15] fix(router): remove app from $router.apps array once
 app destroyed (Fixes #2639)

Prevent destroyed apps from causing memory leak in `$router.apps` array.

Fixes #2639
---
 src/index.js | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/index.js b/src/index.js
index 69c3cc0c8..5c9d9abfc 100644
--- a/src/index.js
+++ b/src/index.js
@@ -91,7 +91,12 @@ export default class VueRouter {
 
     // main app already initialized.
     if (this.app) {
-      return
+     app.$once('hook:destroyed', () {
+       // Clean out app from this.apps array once destroyed
+       const index = this.apps.indexOf(app)
+       if (index > -1) this.apps.splice(index, 1)
+     })
+     return
     }
 
     this.app = app

From 642e80d7434a70d8f83e14b17327938a1e0197b0 Mon Sep 17 00:00:00 2001
From: Troy Morehouse <troymore@nbnet.nb.ca>
Date: Tue, 5 Mar 2019 03:42:12 -0400
Subject: [PATCH 02/15] lint

---
 src/index.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/index.js b/src/index.js
index 5c9d9abfc..1d5afaca1 100644
--- a/src/index.js
+++ b/src/index.js
@@ -91,7 +91,7 @@ export default class VueRouter {
 
     // main app already initialized.
     if (this.app) {
-     app.$once('hook:destroyed', () {
+     app.$once('hook:destroyed', () => {
        // Clean out app from this.apps array once destroyed
        const index = this.apps.indexOf(app)
        if (index > -1) this.apps.splice(index, 1)

From a8cd5af4522f417a785f0770551d7a7f13d7c28f Mon Sep 17 00:00:00 2001
From: Troy Morehouse <troymore@nbnet.nb.ca>
Date: Tue, 5 Mar 2019 03:44:32 -0400
Subject: [PATCH 03/15] lint

---
 src/index.js | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/index.js b/src/index.js
index 1d5afaca1..726cce87a 100644
--- a/src/index.js
+++ b/src/index.js
@@ -91,12 +91,12 @@ export default class VueRouter {
 
     // main app already initialized.
     if (this.app) {
-     app.$once('hook:destroyed', () => {
-       // Clean out app from this.apps array once destroyed
-       const index = this.apps.indexOf(app)
-       if (index > -1) this.apps.splice(index, 1)
-     })
-     return
+      app.$once('hook:destroyed', () => {
+        // Clean out app from this.apps array once destroyed
+        const index = this.apps.indexOf(app)
+        if (index > -1) this.apps.splice(index, 1)
+      })
+      return
     }
 
     this.app = app

From ed1d5d006d594476a1cbfa738ba26fef7893c1d0 Mon Sep 17 00:00:00 2001
From: Troy Morehouse <troymore@nbnet.nb.ca>
Date: Fri, 29 Mar 2019 23:59:55 -0300
Subject: [PATCH 04/15] Update index.js

---
 src/index.js | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/index.js b/src/index.js
index 726cce87a..af5934cf9 100644
--- a/src/index.js
+++ b/src/index.js
@@ -89,13 +89,16 @@ export default class VueRouter {
 
     this.apps.push(app)
 
+    // Clean out app from this.apps array once destroyed
+    app.$once('hook:destroyed', () => {
+      const index = this.apps.indexOf(app)
+      if (index > -1) this.apps.splice(index, 1)
+      // Ensure we still have a main app
+      if (this.apps[0]) this.app = this.apps[0]
+    })
+
     // main app already initialized.
     if (this.app) {
-      app.$once('hook:destroyed', () => {
-        // Clean out app from this.apps array once destroyed
-        const index = this.apps.indexOf(app)
-        if (index > -1) this.apps.splice(index, 1)
-      })
       return
     }
 

From 48b69fbba4051db87237ecbed3f82c3425cfc5c4 Mon Sep 17 00:00:00 2001
From: Troy Morehouse <troymore@nbnet.nb.ca>
Date: Sat, 30 Mar 2019 01:08:59 -0300
Subject: [PATCH 05/15] better handling of last app destroyed

Prevents history listeners from being set up multiple times
---
 src/index.js | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/index.js b/src/index.js
index af5934cf9..a4c876f90 100644
--- a/src/index.js
+++ b/src/index.js
@@ -89,16 +89,22 @@ export default class VueRouter {
 
     this.apps.push(app)
 
-    // Clean out app from this.apps array once destroyed
+    // set up app destroyed handler
     app.$once('hook:destroyed', () => {
+      // clean out app from this.apps array once destroyed
       const index = this.apps.indexOf(app)
       if (index > -1) this.apps.splice(index, 1)
-      // Ensure we still have a main app
-      if (this.apps[0]) this.app = this.apps[0]
+      // ensure we still have a main app, unless this is the last app left
+      if (this.apps.length > 0) this.app = this.apps[0]
     })
 
-    // main app already initialized.
+    // main app previously initialized
     if (this.app) {
+      if (this.app !== this.apps[0]) {
+        // main app had been destroyed, so replace it with this new app
+        this.app = this.apps[0]
+      }
+      // return as we don't need to set up new history listener
       return
     }
 

From bca252bc3905c3fdfc2df612e025dfee62eea80d Mon Sep 17 00:00:00 2001
From: Troy Morehouse <troymore@nbnet.nb.ca>
Date: Sat, 30 Mar 2019 02:06:14 -0300
Subject: [PATCH 06/15] add app destroy testing

---
 test/unit/specs/api.spec.js | 65 +++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)

diff --git a/test/unit/specs/api.spec.js b/test/unit/specs/api.spec.js
index 5fce2e885..e777f910d 100644
--- a/test/unit/specs/api.spec.js
+++ b/test/unit/specs/api.spec.js
@@ -1,4 +1,5 @@
 import Router from '../../../src/index'
+import Vue from 'vue'
 
 describe('router.onReady', () => {
   it('should work', done => {
@@ -185,3 +186,67 @@ describe('router.push/replace callbacks', () => {
     })
   })
 })
+
+describe('router app destroy handling', () => {
+  it('should remove destroyed apps from this.apps', () => {
+    const router = new Router({
+      mode: 'abstract',
+      routes: [
+        { path: '/', component: { name: 'A' }}
+      ]
+    })
+
+    const options = {
+      router,
+      render(h) { return h('div') }
+    }
+
+    expect(router.apps.length).toBe(0)
+    expect(router.app).toBe(null)
+
+    // Add main app
+    const app1 = new Vue(options)
+    expect(router.app).toBe(app1)
+    expect(router.apps.length).toBe(1)
+    expect(router.app[0]).toBe(app1)
+
+    // Add 2nd app
+    const app2 = new Vue(options)
+    expect(router.app).toBe(app1)
+    expect(router.apps.length).toBe(2)
+    expect(router.app[0]).toBe(app1)
+    expect(router.app[1]).toBe(app2)
+
+    // Add 3rd app
+    const app3 = new Vue(options)
+    expect(router.app).toBe(app1)
+    expect(router.apps.length).toBe(3)
+    expect(router.app[0]).toBe(app1)
+    expect(router.app[1]).toBe(app2)
+    expect(router.app[2]).toBe(app3)
+
+    // Destroy second app
+    app2.destroy()
+    expect(router.app).toBe(app1)
+    expect(router.apps.length).toBe(2)
+    expect(router.app[0]).toBe(app1)
+    expect(router.app[1]).toBe(app3)
+
+    // Destroy 1st app
+    app1.destroy()
+    expect(router.app).toBe(app3)
+    expect(router.apps.length).toBe(1)
+    expect(router.app[0]).toBe(app3)
+
+    // Destroy 3rd app
+    app3.destroy()
+    expect(router.app).toBe(app3)
+    expect(router.apps.length).toBe(0)
+
+    // Add 4th app (should be the only app)
+    const app4 = new Vue(options)
+    expect(router.app).toBe(app4)
+    expect(router.apps.length).toBe(1)
+    expect(router.app[0]).toBe(app4)
+  })
+})

From 2696c1086968782bb43b75105cb19ccafb294fe0 Mon Sep 17 00:00:00 2001
From: Troy Morehouse <troymore@nbnet.nb.ca>
Date: Sat, 30 Mar 2019 02:13:19 -0300
Subject: [PATCH 07/15] Update api.spec.js

---
 test/unit/specs/api.spec.js | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/test/unit/specs/api.spec.js b/test/unit/specs/api.spec.js
index e777f910d..f96b9ae76 100644
--- a/test/unit/specs/api.spec.js
+++ b/test/unit/specs/api.spec.js
@@ -196,29 +196,33 @@ describe('router app destroy handling', () => {
       ]
     })
 
-    const options = {
-      router,
-      render(h) { return h('div') }
-    }
-
     expect(router.apps.length).toBe(0)
     expect(router.app).toBe(null)
 
     // Add main app
-    const app1 = new Vue(options)
+    const app1 = new Vue({
+      router,
+      render (h) { return h('div') }
+    })
     expect(router.app).toBe(app1)
     expect(router.apps.length).toBe(1)
     expect(router.app[0]).toBe(app1)
 
     // Add 2nd app
-    const app2 = new Vue(options)
+    const app2 = new Vue({
+      router,
+      render (h) { return h('div') }
+    })
     expect(router.app).toBe(app1)
     expect(router.apps.length).toBe(2)
     expect(router.app[0]).toBe(app1)
     expect(router.app[1]).toBe(app2)
 
     // Add 3rd app
-    const app3 = new Vue(options)
+    const app3 = new Vue({
+      router,
+      render (h) { return h('div') }
+    })
     expect(router.app).toBe(app1)
     expect(router.apps.length).toBe(3)
     expect(router.app[0]).toBe(app1)
@@ -226,25 +230,28 @@ describe('router app destroy handling', () => {
     expect(router.app[2]).toBe(app3)
 
     // Destroy second app
-    app2.destroy()
+    app2.$destroy()
     expect(router.app).toBe(app1)
     expect(router.apps.length).toBe(2)
     expect(router.app[0]).toBe(app1)
     expect(router.app[1]).toBe(app3)
 
     // Destroy 1st app
-    app1.destroy()
+    app1.$destroy()
     expect(router.app).toBe(app3)
     expect(router.apps.length).toBe(1)
     expect(router.app[0]).toBe(app3)
 
     // Destroy 3rd app
-    app3.destroy()
+    app3.$destroy()
     expect(router.app).toBe(app3)
     expect(router.apps.length).toBe(0)
 
     // Add 4th app (should be the only app)
-    const app4 = new Vue(options)
+    const app4 = new Vue({
+      router,
+      render (h) { return h('div') }
+    })
     expect(router.app).toBe(app4)
     expect(router.apps.length).toBe(1)
     expect(router.app[0]).toBe(app4)

From fe214b2aee4735e019a34cc81e5b8d6803c99874 Mon Sep 17 00:00:00 2001
From: Troy Morehouse <troymore@nbnet.nb.ca>
Date: Sat, 30 Mar 2019 02:24:07 -0300
Subject: [PATCH 08/15] Update api.spec.js

---
 test/unit/specs/api.spec.js | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/test/unit/specs/api.spec.js b/test/unit/specs/api.spec.js
index f96b9ae76..ca5e8b61d 100644
--- a/test/unit/specs/api.spec.js
+++ b/test/unit/specs/api.spec.js
@@ -189,6 +189,8 @@ describe('router.push/replace callbacks', () => {
 
 describe('router app destroy handling', () => {
   it('should remove destroyed apps from this.apps', () => {
+    Vue.use(Router)
+
     const router = new Router({
       mode: 'abstract',
       routes: [

From 87edd99d3db770eb91262528c4c5ddfd20eaa1e0 Mon Sep 17 00:00:00 2001
From: Troy Morehouse <troymore@nbnet.nb.ca>
Date: Sat, 30 Mar 2019 02:46:10 -0300
Subject: [PATCH 09/15] Update api.spec.js

---
 test/unit/specs/api.spec.js | 119 ++++++++++++++++++++----------------
 1 file changed, 66 insertions(+), 53 deletions(-)

diff --git a/test/unit/specs/api.spec.js b/test/unit/specs/api.spec.js
index ca5e8b61d..d9e15b69c 100644
--- a/test/unit/specs/api.spec.js
+++ b/test/unit/specs/api.spec.js
@@ -188,74 +188,87 @@ describe('router.push/replace callbacks', () => {
 })
 
 describe('router app destroy handling', () => {
-  it('should remove destroyed apps from this.apps', () => {
-    Vue.use(Router)
+  Vue.use(Router)
 
-    const router = new Router({
-      mode: 'abstract',
-      routes: [
-        { path: '/', component: { name: 'A' }}
-      ]
-    })
+  const router = new Router({
+    mode: 'abstract',
+    routes: [
+      { path: '/', component: { name: 'A' }}
+    ]
+  })
 
-    expect(router.apps.length).toBe(0)
-    expect(router.app).toBe(null)
+  // Add main app
+  const app1 = new Vue({
+    router,
+    render (h) { return h('div') }
+  })
 
-    // Add main app
-    const app1 = new Vue({
-      router,
-      render (h) { return h('div') }
-    })
-    expect(router.app).toBe(app1)
-    expect(router.apps.length).toBe(1)
-    expect(router.app[0]).toBe(app1)
+  // Add 2nd app
+  const app2 = new Vue({
+    router,
+    render (h) { return h('div') }
+  })
 
-    // Add 2nd app
-    const app2 = new Vue({
-      router,
-      render (h) { return h('div') }
-    })
-    expect(router.app).toBe(app1)
-    expect(router.apps.length).toBe(2)
-    expect(router.app[0]).toBe(app1)
-    expect(router.app[1]).toBe(app2)
+  // Add 3rd app
+  const app3 = new Vue({
+    router,
+    render (h) { return h('div') }
+  })
 
-    // Add 3rd app
-    const app3 = new Vue({
-      router,
-      render (h) { return h('div') }
-    })
-    expect(router.app).toBe(app1)
-    expect(router.apps.length).toBe(3)
-    expect(router.app[0]).toBe(app1)
-    expect(router.app[1]).toBe(app2)
-    expect(router.app[2]).toBe(app3)
+  it('router and apps should be defined', async () => {
+    expect(router).toBeDefined()
+    expect(router).toBeInstanceOf(Router)
+    expect(app1).toBeDefined()
+    expect(app1).toBeInstanceOf(Vue)
+    expect(app2).toBeDefined()
+    expect(app2).toBeInstanceOf(Vue)
+    expect(app3).toBeDefined()
+    expect(app3).toBeInstanceOf(Vue)
+    expect(app1.$router.apps).toBe(app2.$router.apps)
+    expect(app2.$router.apps).toBe(app3.$router.apps)
+  })
+
+  it('should have 3 registered apps', async () => {
+    expect(app1.$router).toBeDefined()
+    expect(app1.$router.app).toBe(app1)
+    expect(app1.$router.apps.length).toBe(3)
+    expect(app1.$router.apps[0]).toBe(app1)
+    expect(app1.$router.apps[1]).toBe(app2)
+    expect(app1.$router.apps[2]).toBe(app3)
+  })
 
-    // Destroy second app
+  it('should remove 2nd destroyed app from this.apps', async () => {
     app2.$destroy()
-    expect(router.app).toBe(app1)
-    expect(router.apps.length).toBe(2)
-    expect(router.app[0]).toBe(app1)
-    expect(router.app[1]).toBe(app3)
+    await Vue.nextTick()
+    expect(app1.$router.app).toBe(app1)
+    expect(app1.$router.apps.length).toBe(2)
+    expect(app1.$router.app[0]).toBe(app1)
+    expect(app1.$router.app[1]).toBe(app3)
+  })
 
-    // Destroy 1st app
+  it('should remove 1st destroyed app from this.apps and replace this.app', async () => {
     app1.$destroy()
-    expect(router.app).toBe(app3)
-    expect(router.apps.length).toBe(1)
-    expect(router.app[0]).toBe(app3)
+    await Vue.nextTick()
+    expect(app3.$router.app).toBe(app3)
+    expect(app3.$router.apps.length).toBe(1)
+    expect(app3.$router.app[0]).toBe(app3)
+  })
 
-    // Destroy 3rd app
+  it('should remove last destroyed app from this.apps', async () => {
     app3.$destroy()
-    expect(router.app).toBe(app3)
-    expect(router.apps.length).toBe(0)
+    await Vue.nextTick()
+    expect(app3.$router.app).toBe(app3)
+    expect(app3.$router.apps.length).toBe(0)
+  })
 
-    // Add 4th app (should be the only app)
+  it('should replace app with new app', async () => {
     const app4 = new Vue({
       router,
       render (h) { return h('div') }
     })
-    expect(router.app).toBe(app4)
-    expect(router.apps.length).toBe(1)
-    expect(router.app[0]).toBe(app4)
+    await Vue.nextTick()
+    expect(app4.$router.app).toBe(app4)
+    expect(app4.$router.apps.length).toBe(1)
+    expect(app4.$router.app[0]).toBe(app4)
   })
 })

From aa204e9b38642ff1a3458610c77a4b8da00fd836 Mon Sep 17 00:00:00 2001
From: Troy Morehouse <troymore@nbnet.nb.ca>
Date: Sat, 30 Mar 2019 02:52:54 -0300
Subject: [PATCH 10/15] Update api.spec.js

---
 test/unit/specs/api.spec.js | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/test/unit/specs/api.spec.js b/test/unit/specs/api.spec.js
index d9e15b69c..30b9a7752 100644
--- a/test/unit/specs/api.spec.js
+++ b/test/unit/specs/api.spec.js
@@ -215,7 +215,7 @@ describe('router app destroy handling', () => {
     render (h) { return h('div') }
   })
 
-  it('router and apps should be defined', async () => {
+  it('router and apps should be defined', () => {
     expect(router).toBeDefined()
     expect(router).toBeInstanceOf(Router)
     expect(app1).toBeDefined()
@@ -228,7 +228,7 @@ describe('router app destroy handling', () => {
     expect(app2.$router.apps).toBe(app3.$router.apps)
   })
 
-  it('should have 3 registered apps', async () => {
+  it('should have 3 registered apps', () => {
     expect(app1.$router).toBeDefined()
     expect(app1.$router.app).toBe(app1)
     expect(app1.$router.apps.length).toBe(3)
@@ -237,36 +237,32 @@ describe('router app destroy handling', () => {
     expect(app1.$router.apps[2]).toBe(app3)
   })
 
-  it('should remove 2nd destroyed app from this.apps', async () => {
+  it('should remove 2nd destroyed app from this.apps', () => {
     app2.$destroy()
-    await Vue.nextTick()
     expect(app1.$router.app).toBe(app1)
     expect(app1.$router.apps.length).toBe(2)
     expect(app1.$router.app[0]).toBe(app1)
     expect(app1.$router.app[1]).toBe(app3)
   })
 
-  it('should remove 1st destroyed app from this.apps and replace this.app', async () => {
+  it('should remove 1st destroyed app from this.apps and replace this.app', () => {
     app1.$destroy()
-    await Vue.nextTick()
     expect(app3.$router.app).toBe(app3)
     expect(app3.$router.apps.length).toBe(1)
     expect(app3.$router.app[0]).toBe(app3)
   })
 
-  it('should remove last destroyed app from this.apps', async () => {
+  it('should remove last destroyed app from this.apps', () => {
     app3.$destroy()
-    await Vue.nextTick()
     expect(app3.$router.app).toBe(app3)
     expect(app3.$router.apps.length).toBe(0)
   })
 
-  it('should replace app with new app', async () => {
+  it('should replace app with new app', () => {
     const app4 = new Vue({
       router,
       render (h) { return h('div') }
     })
-    await Vue.nextTick()
     expect(app4.$router.app).toBe(app4)
     expect(app4.$router.apps.length).toBe(1)
     expect(app4.$router.app[0]).toBe(app4)

From b540487671b319e813d93910a86526baeb3b3a2a Mon Sep 17 00:00:00 2001
From: Troy Morehouse <troymore@nbnet.nb.ca>
Date: Sat, 30 Mar 2019 02:59:37 -0300
Subject: [PATCH 11/15] Update api.spec.js

---
 test/unit/specs/api.spec.js | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/test/unit/specs/api.spec.js b/test/unit/specs/api.spec.js
index 30b9a7752..ef3f3d51d 100644
--- a/test/unit/specs/api.spec.js
+++ b/test/unit/specs/api.spec.js
@@ -217,15 +217,17 @@ describe('router app destroy handling', () => {
 
   it('router and apps should be defined', () => {
     expect(router).toBeDefined()
-    expect(router).toBeInstanceOf(Router)
+    expect(router istanceof Router).toBe(true)
     expect(app1).toBeDefined()
-    expect(app1).toBeInstanceOf(Vue)
+    expect(app1 instanceof Vue).toBe(true)
     expect(app2).toBeDefined()
-    expect(app2).toBeInstanceOf(Vue)
+    expect(app2 instanceof Vue).toBe(true)
     expect(app3).toBeDefined()
-    expect(app3).toBeInstanceOf(Vue)
+    expect(app3 instanceof Vue).toBe(true)
     expect(app1.$router.apps).toBe(app2.$router.apps)
     expect(app2.$router.apps).toBe(app3.$router.apps)
+    expect(app1.$router.app).toBe(app2.$router.app)
+    expect(app2.$router.app).toBe(app3.$router.app)
   })
 
   it('should have 3 registered apps', () => {

From a31748ee5220246aba7ec9b3494d960ab66491cb Mon Sep 17 00:00:00 2001
From: Troy Morehouse <troymore@nbnet.nb.ca>
Date: Sat, 30 Mar 2019 03:02:16 -0300
Subject: [PATCH 12/15] Update api.spec.js

---
 test/unit/specs/api.spec.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/unit/specs/api.spec.js b/test/unit/specs/api.spec.js
index ef3f3d51d..63b172d0e 100644
--- a/test/unit/specs/api.spec.js
+++ b/test/unit/specs/api.spec.js
@@ -217,7 +217,7 @@ describe('router app destroy handling', () => {
 
   it('router and apps should be defined', () => {
     expect(router).toBeDefined()
-    expect(router istanceof Router).toBe(true)
+    expect(router instanceof Router).toBe(true)
     expect(app1).toBeDefined()
     expect(app1 instanceof Vue).toBe(true)
     expect(app2).toBeDefined()

From f49415e0cba77c860efcb2329a84856495895d9a Mon Sep 17 00:00:00 2001
From: Troy Morehouse <troymore@nbnet.nb.ca>
Date: Sat, 30 Mar 2019 03:06:26 -0300
Subject: [PATCH 13/15] Update api.spec.js

---
 test/unit/specs/api.spec.js | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/test/unit/specs/api.spec.js b/test/unit/specs/api.spec.js
index 63b172d0e..75abdb2cd 100644
--- a/test/unit/specs/api.spec.js
+++ b/test/unit/specs/api.spec.js
@@ -241,17 +241,19 @@ describe('router app destroy handling', () => {
 
   it('should remove 2nd destroyed app from this.apps', () => {
     app2.$destroy()
+    expect(app1.$router).toBeDefined()
+    expect(app1.$router.app).toBeDefined()
     expect(app1.$router.app).toBe(app1)
     expect(app1.$router.apps.length).toBe(2)
-    expect(app1.$router.app[0]).toBe(app1)
-    expect(app1.$router.app[1]).toBe(app3)
+    expect(app1.$router.apps[0]).toBe(app1)
+    expect(app1.$router.apps[1]).toBe(app3)
   })
 
   it('should remove 1st destroyed app from this.apps and replace this.app', () => {
     app1.$destroy()
     expect(app3.$router.app).toBe(app3)
     expect(app3.$router.apps.length).toBe(1)
-    expect(app3.$router.app[0]).toBe(app3)
+    expect(app3.$router.apps[0]).toBe(app3)
   })
 
   it('should remove last destroyed app from this.apps', () => {
@@ -267,6 +269,6 @@ describe('router app destroy handling', () => {
     })
     expect(app4.$router.app).toBe(app4)
     expect(app4.$router.apps.length).toBe(1)
-    expect(app4.$router.app[0]).toBe(app4)
+    expect(app4.$router.apps[0]).toBe(app4)
   })
 })

From 009736d9f743ee3d03116f769275e3d7e49cdaa9 Mon Sep 17 00:00:00 2001
From: Eduardo San Martin Morote <posva13@gmail.com>
Date: Thu, 11 Apr 2019 12:07:06 +0200
Subject: [PATCH 14/15] refactor: code review

---
 src/index.js                | 16 +++---
 test/unit/specs/api.spec.js | 98 ++++++++++++++++++++-----------------
 2 files changed, 62 insertions(+), 52 deletions(-)

diff --git a/src/index.js b/src/index.js
index a4c876f90..8ca98003c 100644
--- a/src/index.js
+++ b/src/index.js
@@ -90,21 +90,23 @@ export default class VueRouter {
     this.apps.push(app)
 
     // set up app destroyed handler
+    // https://github.com/vuejs/vue-router/issues/2639
     app.$once('hook:destroyed', () => {
       // clean out app from this.apps array once destroyed
       const index = this.apps.indexOf(app)
       if (index > -1) this.apps.splice(index, 1)
-      // ensure we still have a main app, unless this is the last app left
-      if (this.apps.length > 0) this.app = this.apps[0]
+      // ensure we still have a main app
+      if (this.app === app) this.app = this.apps[0] || null
+      // no more apps, the router can be released
+      if (!this.app) {
+        // TODO: destroy router, listeners?
+        // Maybe the user wants to reuse the router though
+      }
     })
 
     // main app previously initialized
+    // return as we don't need to set up new history listener
     if (this.app) {
-      if (this.app !== this.apps[0]) {
-        // main app had been destroyed, so replace it with this new app
-        this.app = this.apps[0]
-      }
-      // return as we don't need to set up new history listener
       return
     }
 
diff --git a/test/unit/specs/api.spec.js b/test/unit/specs/api.spec.js
index 75abdb2cd..1fba4977b 100644
--- a/test/unit/specs/api.spec.js
+++ b/test/unit/specs/api.spec.js
@@ -190,48 +190,41 @@ describe('router.push/replace callbacks', () => {
 describe('router app destroy handling', () => {
   Vue.use(Router)
 
-  const router = new Router({
-    mode: 'abstract',
-    routes: [
-      { path: '/', component: { name: 'A' }}
-    ]
-  })
+  let router, app1, app2, app3
 
-  // Add main app
-  const app1 = new Vue({
-    router,
-    render (h) { return h('div') }
-  })
+  beforeEach(() => {
+    router = new Router({
+      mode: 'abstract',
+      routes: [
+        { path: '/', component: { name: 'A' }}
+      ]
+    })
 
-  // Add 2nd app
-  const app2 = new Vue({
-    router,
-    render (h) { return h('div') }
-  })
+    // Add main app
+    app1 = new Vue({
+      router,
+      render (h) { return h('div') }
+    })
+
+    // Add 2nd app
+    app2 = new Vue({
+      router,
+      render (h) { return h('div') }
+    })
 
-  // Add 3rd app
-  const app3 = new Vue({
-    router,
-    render (h) { return h('div') }
+    // Add 3rd app
+    app3 = new Vue({
+      router,
+      render (h) { return h('div') }
+    })
   })
 
-  it('router and apps should be defined', () => {
-    expect(router).toBeDefined()
-    expect(router instanceof Router).toBe(true)
-    expect(app1).toBeDefined()
-    expect(app1 instanceof Vue).toBe(true)
-    expect(app2).toBeDefined()
-    expect(app2 instanceof Vue).toBe(true)
-    expect(app3).toBeDefined()
-    expect(app3 instanceof Vue).toBe(true)
-    expect(app1.$router.apps).toBe(app2.$router.apps)
-    expect(app2.$router.apps).toBe(app3.$router.apps)
-    expect(app1.$router.app).toBe(app2.$router.app)
-    expect(app2.$router.app).toBe(app3.$router.app)
+  it('all apps point to the same router instance', () => {
+    expect(app1.$router).toBe(app2.$router)
+    expect(app2.$router).toBe(app3.$router)
   })
 
-  it('should have 3 registered apps', () => {
-    expect(app1.$router).toBeDefined()
+  it('should have all 3 registered apps', () => {
     expect(app1.$router.app).toBe(app1)
     expect(app1.$router.apps.length).toBe(3)
     expect(app1.$router.apps[0]).toBe(app1)
@@ -241,33 +234,48 @@ describe('router app destroy handling', () => {
 
   it('should remove 2nd destroyed app from this.apps', () => {
     app2.$destroy()
-    expect(app1.$router).toBeDefined()
-    expect(app1.$router.app).toBeDefined()
     expect(app1.$router.app).toBe(app1)
     expect(app1.$router.apps.length).toBe(2)
     expect(app1.$router.apps[0]).toBe(app1)
     expect(app1.$router.apps[1]).toBe(app3)
   })
 
-  it('should remove 1st destroyed app from this.apps and replace this.app', () => {
+  it('should remove 1st destroyed app and replace current app', () => {
     app1.$destroy()
-    expect(app3.$router.app).toBe(app3)
-    expect(app3.$router.apps.length).toBe(1)
-    expect(app3.$router.apps[0]).toBe(app3)
+    expect(app3.$router.app).toBe(app2)
+    expect(app3.$router.apps.length).toBe(2)
+    expect(app3.$router.apps[0]).toBe(app2)
+    expect(app1.$router.apps[1]).toBe(app3)
   })
 
-  it('should remove last destroyed app from this.apps', () => {
+  it('should remove all apps', () => {
+    app1.$destroy()
     app3.$destroy()
-    expect(app3.$router.app).toBe(app3)
+    app2.$destroy()
+    expect(app3.$router.app).toBe(null)
     expect(app3.$router.apps.length).toBe(0)
   })
 
-  it('should replace app with new app', () => {
+  it('should keep current app if already defined', () => {
+    const app4 = new Vue({
+      router,
+      render (h) { return h('div') }
+    })
+    expect(app4.$router.app).toBe(app1)
+    expect(app4.$router.apps.length).toBe(4)
+    expect(app4.$router.apps[3]).toBe(app4)
+  })
+
+  it('should replace current app if none is assigned when creating the app', () => {
+    app1.$destroy()
+    app3.$destroy()
+    app2.$destroy()
     const app4 = new Vue({
       router,
       render (h) { return h('div') }
     })
-    expect(app4.$router.app).toBe(app4)
+    expect(router.app).toBe(app4)
+    expect(app4.$router).toBe(router)
     expect(app4.$router.apps.length).toBe(1)
     expect(app4.$router.apps[0]).toBe(app4)
   })

From 47c0920d53d4f251a09446faaf924a7150bc6854 Mon Sep 17 00:00:00 2001
From: Eduardo San Martin Morote <posva13@gmail.com>
Date: Thu, 11 Apr 2019 12:09:47 +0200
Subject: [PATCH 15/15] refactor: remove unused code

---
 src/index.js | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/src/index.js b/src/index.js
index 8ca98003c..b3eb25dd3 100644
--- a/src/index.js
+++ b/src/index.js
@@ -95,13 +95,9 @@ export default class VueRouter {
       // clean out app from this.apps array once destroyed
       const index = this.apps.indexOf(app)
       if (index > -1) this.apps.splice(index, 1)
-      // ensure we still have a main app
+      // ensure we still have a main app or null if no apps
+      // we do not release the router so it can be reused
       if (this.app === app) this.app = this.apps[0] || null
-      // no more apps, the router can be released
-      if (!this.app) {
-        // TODO: destroy router, listeners?
-        // Maybe the user wants to reuse the router though
-      }
     })
 
     // main app previously initialized