fix: workaround for memoryleak in destroyed hook

src/shared/mixin.js

@@ -29,7 +29,10 @@ export default function createMixin (Vue, options) {
       // Add a marker to know if it uses metaInfo
       // _vnode is used to know that it's attached to a real component
       // useful if we use some mixin to add some meta tags (like nuxt-i18n)
-      if (!isUndefined(this.$options[options.keyName]) && this.$options[options.keyName] !== null) {
+      if (isUndefined(this.$options[options.keyName]) || this.$options[options.keyName] === null) {
+        return
+      }
+
       if (!this.$root._vueMeta) {
         this.$root._vueMeta = { appId }
         appId++
@@ -62,7 +65,8 @@ export default function createMixin (Vue, options) {
           // when it changes (i.e. automatically handle async actions that affect metaInfo)
           // credit for this suggestion goes to [Sébastien Chopin](https://github.com/Atinux)
           ensuredPush(this.$options, 'created', () => {
-              this.$watch('$metaInfo', function () {
+            this.$watch('$metaInfo', () => {
+              this.__metaInfo = undefined
               triggerUpdate(this, 'watcher')
             })
           })
@@ -126,33 +130,35 @@ export default function createMixin (Vue, options) {
       }
 
       // do not trigger refresh on the server side
-        if (!this.$isServer) {
+      if (this.$isServer) {
+        return
+      }
+
       // no need to add this hooks on server side
       updateOnLifecycleHook.forEach((lifecycleHook) => {
         ensuredPush(this.$options, lifecycleHook, () => triggerUpdate(this, lifecycleHook))
       })
+    },
+    // TODO: move back into beforeCreate when Vue issue is resolved
+    destroyed () {
+      // do not trigger refresh:
+      // - on the server side
+      // - when the component doesnt have a parent
+      // - doesnt have metaInfo defined
+      if (this.$isServer || !this.$parent || !hasMetaInfo(this)) {
+        return
+      }
 
-          // re-render meta data when returning from a child component to parent
-          ensuredPush(this.$options, 'destroyed', () => {
       // Wait that element is hidden before refreshing meta tags (to support animations)
       const interval = setInterval(() => {
         if (this.$el && this.$el.offsetParent !== null) {
-                /* istanbul ignore next line */
           return
         }
 
         clearInterval(interval)
 
-              if (!this.$parent) {
-                /* istanbul ignore next line */
-                return
-              }
-
         triggerUpdate(this, 'destroyed')
       }, 50)
-          })
-        }
-      }
     }
   }
 }