MD Bookmarks: Prevent navigating to invalid folders

chrome/browser/resources/md_bookmarks/router.js

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 Polymer({
   /**
    * This element is a one way bound interface that routes the page URL to
    * the searchTerm and selectedId. Clients must initialize themselves by
    * reading the router's fields after attach.
    */
@@ skipping 24 matching lines @@
     'onStateChanged_(searchTerm_, selectedId_)',
   ],
 
   attached: function() {
     this.watch('selectedId_', function(state) {
       return state.selectedFolder;
     });
     this.watch('searchTerm_', function(state) {
       return state.search.term;
     });
+    this.updateFromStore();
   },
 
   /** @private */
   onQueryChanged_: function() {
     var searchTerm = this.queryParams_.q || '';
     if (searchTerm && searchTerm != this.searchTerm_) {
       this.searchTerm_ = searchTerm;
       this.dispatch(bookmarks.actions.setSearchTerm(searchTerm));
     }
   },
 
   /** @private */
   onFolderChanged_: function() {
     var selectedId = this.queryParams_.id;
     if (selectedId && selectedId != this.selectedId_) {
       this.selectedId_ = selectedId;
-      this.dispatch(bookmarks.actions.selectFolder(selectedId));
+      // Need to dispatch a deferred action so that during page load
+      // `this.getState()` will only evaluate after the Store is initialized.
+      this.dispatch(function(dispatch) {
+        dispatch(
+            bookmarks.actions.selectFolder(selectedId, this.getState().nodes));
+      }.bind(this));

[calamity, 2017/05/02 08:27:15]

So... If I understand correctly, the deferred action here prevents
this.getState() from being called before the store is initialized by pushing the
evaluation as a function into queuedActions?

Neat.

[tsergeant, 2017/05/03 02:57:31]

Yup, that's the idea.

     }
   },
 
   /** @private */
   onStateChanged_: function() {
     this.debounce('updateQueryParams', this.updateQueryParams_.bind(this));
   },
 
   /** @private */
   updateQueryParams_: function() {
     if (this.searchTerm_)
       this.queryParams_ = {q: this.searchTerm_};
     else
       this.queryParams_ = {id: this.selectedId_};
   },
 });