MD Bookmarks: Prevent navigating to invalid folders

chrome/browser/resources/md_bookmarks/actions.js

Index: chrome/browser/resources/md_bookmarks/actions.js
diff --git a/chrome/browser/resources/md_bookmarks/actions.js b/chrome/browser/resources/md_bookmarks/actions.js
index 9f6a63d11ab0d670608a17b3c0fae6f2cb4fba1a..8f52ef8a34b7481efa5b9ee1c0c622610d22ae43 100644
--- a/chrome/browser/resources/md_bookmarks/actions.js
+++ b/chrome/browser/resources/md_bookmarks/actions.js
@@ -97,10 +97,15 @@ cr.define('bookmarks.actions', function() {
 
   /**
    * @param {string} id
+   * @param {NodeList} nodes Current node state. Can be ommitted in tests.

[calamity, 2017/04/11 04:13:37]

Doesn't omitting this always result in a no-op? When would that be useful?

[tsergeant, 2017/05/02 03:20:24]

If nodes is falsey, the check for validity will be skipped entirely, and a
select-folder action will always be returned. This is useful in tests that don't
care about the validity check.

    * @return {!Action}
    */
-  function selectFolder(id) {
-    assert(id != '0', 'Cannot select root folder');
+  function selectFolder(id, nodes) {
+    if (nodes && (id == ROOT_NODE_ID || !nodes[id] || nodes[id].url)) {
+      return {
+        name: 'no-op',
+      };

[calamity, 2017/04/11 04:13:37]

Make no-op a private action and early return in reduceAction.

[tsergeant, 2017/05/02 03:20:24]

I've replace 'no-op' with returning null, which does exactly that.

+    }
     return {
       name: 'select-folder',
       id: id,