chrome://snippets-internals page for debugging NTP snippets.

chrome/browser/resources/snippets_internals.js

+// Copyright 2015 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.
+
+cr.define('chrome.snippets_internals', function() {
+  'use strict';
+
+  function initialize() {
+    function submitDownload(event) {
+      chrome.send('download', [$('hosts-input').value]);
+      event.preventDefault();
+    }
+
+    $('submit-download').addEventListener('click', submitDownload);
+
+    function submitClear(event) {
+      chrome.send('clear');
+      event.preventDefault();
+    }
+
+    $('submit-clear').addEventListener('click', submitClear);
+
+    function clearDiscarded(event) {

[Marc Treib, 2016/04/13 08:45:51]

submitClearDiscarded, for consistency?

[jkrcal, 2016/04/14 15:27:00]

Done.

+      chrome.send('clearDiscarded');
+      event.preventDefault();
+    }
+
+    $('discarded-snippets-clear').addEventListener('click', clearDiscarded);
+
+    chrome.send('loaded');
+  }
+
+  function receiveProperty(propertyId, value) {
+    if ($(propertyId)) $(propertyId).textContent = value;
+  }
+
+  function receiveHostsInput(value) {
+    $('hosts-input').value = value;
+  }
+
+  function receiveHosts(hosts) {
+    displayList(hosts, 'hosts');
+  }
+
+  function receiveSnippets(snippets) {
+    displayList(snippets, 'snippets', 'snippet-title');
+  }
+
+  function receiveDiscardedSnippets(discardedSnippets) {
+    displayList(discardedSnippets, 'discarded-snippets',
+                'discarded-snippet-title');
+  }
+
+  function trigger(event) {
+    // The id of the div to (un)hide is stored to 'myid' attribute of the link.
+    var id = event.currentTarget.getAttribute('myid');
+    if ($(id)) $(id).classList.toggle('snippet-hidden');
+  }
+
+  function displayList(object, domId, titleClass) {
+    if (object == null || !object.list || object.list.constructor !== Array)

[Marc Treib, 2016/04/13 08:45:51]

Are these checks actually required in any legitimate case? If so, please add a
comment saying in which cases this can actually happen. Otherwise, please remove
the checks - if something goes wrong, we'd like to notice, rather than silently
swallowing the error.

[jkrcal, 2016/04/14 15:27:00]

Done.

+      return;
+
+    jstProcess(new JsEvalContext(object), $(domId));
+
+    var text;
+    var display;
+
+    if (object.list.length > 0) {
+      text = '';
+      display = 'inline';
+    } else {
+      text = 'The list is empty.';
+      display = 'none';
+    }
+
+    if ($(domId + '-empty')) $(domId + '-empty').textContent = text;
+    if ($(domId + '-clear')) $(domId + '-clear').style.display = display;
+
+    var links = document.getElementsByClassName(titleClass);
+    for (var link of links) {
+      link.addEventListener('click', trigger);
+    }
+  }
+
+  // Return an object with all of the exports.
+  return {
+    initialize: initialize,
+    receiveProperty: receiveProperty,
+    receiveHostsInput: receiveHostsInput,
+    receiveHosts: receiveHosts,
+    receiveSnippets: receiveSnippets,
+    receiveDiscardedSnippets: receiveDiscardedSnippets,
+    trigger: trigger,

[Marc Treib, 2016/04/13 08:45:51]

I think "trigger" doesn't need to be listed here.

[jkrcal, 2016/04/14 15:27:00]

Done.

+  };
+});
+
+document.addEventListener('DOMContentLoaded',
+                          chrome.snippets_internals.initialize);