From f2e8eb537d0ff5edad9aca865c5cacc9e5e41edc Mon Sep 17 00:00:00 2001
From: pimlie <pimlie@hotmail.com>
Date: Fri, 8 Mar 2019 13:11:01 +0100
Subject: [PATCH] feat: track branches which contain metaInfo components

---
 src/shared/inMetaInfoBranch.js |  6 ++++++
 src/shared/mixin.js            | 15 +++++++++++++--
 2 files changed, 19 insertions(+), 2 deletions(-)
 create mode 100644 src/shared/inMetaInfoBranch.js

diff --git a/src/shared/inMetaInfoBranch.js b/src/shared/inMetaInfoBranch.js
new file mode 100644
index 0000000..e2884d9
--- /dev/null
+++ b/src/shared/inMetaInfoBranch.js
@@ -0,0 +1,6 @@
+import { isUndefined } from './typeof'
+
+// a component is in a metaInfo branch when itself has meta info or one of its (grand-)children has
+export default function inMetaInfoBranch(vm = this) {
+  return vm && !isUndefined(vm._vueMeta)
+}
diff --git a/src/shared/mixin.js b/src/shared/mixin.js
index 8bd2795..c47167d 100644
--- a/src/shared/mixin.js
+++ b/src/shared/mixin.js
@@ -1,4 +1,5 @@
 import triggerUpdate from '../client/triggerUpdate'
+import hasMetaInfo from './hasMetaInfo'
 import { isUndefined, isFunction } from './typeof'
 import { ensuredPush } from './ensure'
 
@@ -16,7 +17,7 @@ export default function createMixin(Vue, options) {
             console.warn('VueMeta DeprecationWarning: _hasMetaInfo has been deprecated and will be removed in a future version. Please import hasMetaInfo and use hasMetaInfo(vm) instead') // eslint-disable-line no-console
             this.$root._vueMeta.hasMetaInfoDeprecationWarningShown = true
           }
-          return !!this._vueMeta
+          return hasMetaInfo(this)
         }
       })
 
@@ -28,8 +29,18 @@ export default function createMixin(Vue, options) {
           this.$root._vueMeta = {}
         }
 
+        // to speed up updates we keep track of branches which have a component with vue-meta info defined
+        // if _vueMeta = true it has info, if _vueMeta = false a child has info
         if (!this._vueMeta) {
           this._vueMeta = true
+
+          let p = this.$parent
+          while (p && p !== this.$root) {
+            if (isUndefined(p._vueMeta)) {
+              p._vueMeta = false
+            }
+            p = p.$parent
+          }
         }
 
         // coerce function-style metaInfo to a computed prop so we can observe
@@ -55,7 +66,7 @@ export default function createMixin(Vue, options) {
         // force an initial refresh on page load and prevent other lifecycleHooks
         // to triggerUpdate until this initial refresh is finished
         // this is to make sure that when a page is opened in an inactive tab which
-        // has throttled rAF/timers we still immeditately set the page title
+        // has throttled rAF/timers we still immediately set the page title
         if (isUndefined(this.$root._vueMeta.initialized)) {
           this.$root._vueMeta.initialized = this.$isServer