fix(ssr): Memory leak in poll method, take 2 (fix #2606)

Author: ronald-d-rogers

Diff for: flow/declarations.js

@@ -68,6 +68,7 @@ declare type RouteRecord = {
   regex: RouteRegExp;
   components: Dictionary<any>;
   instances: Dictionary<any>;
+  pendingCbs: Dictionary<Function>;
   name: ?string;
   parent: ?RouteRecord;
   redirect: ?RedirectOption;

Diff for: src/components/view.js

@@ -1,5 +1,6 @@
 import { warn } from '../util/warn'
 import { extend } from '../util/misc'
+import { tryFinalizeTransition } from '../history/base'
 
 export default {
   name: 'RouterView',
@@ -63,13 +64,18 @@ export default {
         (!val && current === vm)
       ) {
         matched.instances[name] = val
+        // if the route transition has already been confirmed then we weren't
+        // able to call the cb during confirmation as the component was not
+        // registered yet, so we call it here.
+        tryFinalizeTransition(matched, name)
       }
     }
 
     // also register instance in prepatch hook
     // in case the same component instance is reused across different routes
     ;(data.hook || (data.hook = {})).prepatch = (_, vnode) => {
       matched.instances[name] = vnode.componentInstance
+      tryFinalizeTransition(matched, name)
     }
 
     // register instance in init hook
@@ -80,6 +86,7 @@ export default {
         vnode.componentInstance !== matched.instances[name]
       ) {
         matched.instances[name] = vnode.componentInstance
+        tryFinalizeTransition(matched, name)
       }
     }
 

Diff for: src/create-route-map.js

@@ -85,6 +85,7 @@ function addRouteRecord (
     regex: compileRouteRegex(normalizedPath, pathToRegexpOptions),
     components: route.components || { default: route.component },
     instances: {},
+    pendingCbs: {},
     name,
     parent,
     matchAs,

Diff for: src/history/base.js

@@ -178,10 +178,9 @@ export class History {
 
     runQueue(queue, iterator, () => {
       const postEnterCbs = []
-      const isValid = () => this.current === route
       // wait until async components are resolved before
       // extracting in-component enter guards
-      const enterGuards = extractEnterGuards(activated, postEnterCbs, isValid)
+      const enterGuards = extractEnterGuards(activated, postEnterCbs)
       const queue = enterGuards.concat(this.router.resolveHooks)
       runQueue(queue, iterator, () => {
         if (this.pending !== route) {
@@ -299,13 +298,12 @@ function bindGuard (guard: NavigationGuard, instance: ?_Vue): ?NavigationGuard {
 function extractEnterGuards (
   activated: Array<RouteRecord>,
   cbs: Array<Function>,
-  isValid: () => boolean
 ): Array<?Function> {
   return extractGuards(
     activated,
     'beforeRouteEnter',
     (guard, _, match, key) => {
-      return bindEnterGuard(guard, match, key, cbs, isValid)
+      return bindEnterGuard(guard, match, key, cbs)
     }
   )
 }
@@ -315,39 +313,27 @@ function bindEnterGuard (
   match: RouteRecord,
   key: string,
   cbs: Array<Function>,
-  isValid: () => boolean
 ): NavigationGuard {
   return function routeEnterGuard (to, from, next) {
     return guard(to, from, cb => {
       if (typeof cb === 'function') {
+        match.pendingCbs[key] = cb
         cbs.push(() => {
-          // #750
-          // if a router-view is wrapped with an out-in transition,
-          // the instance may not have been registered at this time.
-          // we will need to poll for registration until current route
-          // is no longer valid.
-          poll(cb, match.instances, key, isValid)
+          // if the instance is registered call the cb here, otherwise it will
+          // get called when it is registered in the component's lifecycle hooks
+          tryFinalizeTransition(match, key)
         })
       }
       next(cb)
     })
   }
 }
 
-function poll (
-  cb: any, // somehow flow cannot infer this is a function
-  instances: Object,
-  key: string,
-  isValid: () => boolean
-) {
-  if (
-    instances[key] &&
-    !instances[key]._isBeingDestroyed // do not reuse being destroyed instance
-  ) {
-    cb(instances[key])
-  } else if (isValid()) {
-    setTimeout(() => {
-      poll(cb, instances, key, isValid)
-    }, 16)
+export function tryFinalizeTransition (record: RouteRecord, name: string) {
+  if (record.instances[name] && record.pendingCbs[name]) {
+    const instance = record.instances[name]
+    const cb = record.pendingCbs[name]
+    delete record.pendingCbs[name]
+    cb(instance)
   }
 }