Bug 823547 - Store the snippets version along with the snippets.

r=adw

browser/base/content/abouthome/aboutHome.js

@@ -134,6 +134,7 @@ function ensureSnippetsMapThen(aCallback)
     // Populate the cache from the persistent storage.
     let cache = new Map();
     for (let key of [ "snippets-last-update",
+                      "snippets-cached-version",
                       "snippets" ]) {
       cache.set(key, localStorage[key]);
     }
@@ -229,6 +230,14 @@ function loadSnippets()
   if (!gSnippetsMap)
     throw new Error("Snippets map has not properly been initialized");
 
+  // Check cached snippets version.
+  let cachedVersion = gSnippetsMap.get("snippets-cached-version") || 0;
+  let currentVersion = document.documentElement.getAttribute("snippetsVersion");
+  if (cachedVersion < currentVersion) {
+    // The cached snippets are old and unsupported, restart from scratch.
+    gSnippetsMap.clear();
+  }
+
   // Check last snippets update.
   let lastUpdate = gSnippetsMap.get("snippets-last-update");
   let updateURL = document.documentElement.getAttribute("snippetsURL");
@@ -253,6 +262,7 @@ function loadSnippets()
     {
       if (xhr.status == 200) {
         gSnippetsMap.set("snippets", xhr.responseText);
+        gSnippetsMap.set("snippets-cached-version", currentVersion);
       }
       showSnippets();
     };

browser/base/content/browser.js

@@ -2630,6 +2630,7 @@ function BrowserOnAboutPageLoad(doc) {
     // Inject search engine and snippets URL.
     let docElt = doc.documentElement;
     docElt.setAttribute("snippetsURL", AboutHomeUtils.snippetsURL);
+    docElt.setAttribute("snippetsVersion", AboutHomeUtils.snippetsVersion);
     docElt.setAttribute("searchEngineName",
                         AboutHomeUtils.defaultSearchEngine.name);
     docElt.setAttribute("searchEngineURL",

browser/base/content/test/browser_aboutHome.js

@@ -6,6 +6,8 @@ XPCOMUtils.defineLazyModuleGetter(this, "Promise",
   "resource://gre/modules/commonjs/sdk/core/promise.js");
 XPCOMUtils.defineLazyModuleGetter(this, "Task",
   "resource://gre/modules/Task.jsm");
+XPCOMUtils.defineLazyModuleGetter(this, "AboutHomeUtils",
+  "resource:///modules/AboutHomeUtils.jsm");
 
 registerCleanupFunction(function() {
   // Ensure we don't pollute prefs for next tests.
@@ -42,7 +44,7 @@ let gTests = [
     let snippetsElt = doc.getElementById("snippets");
     ok(snippetsElt, "Found snippets element")
     is(snippetsElt.getElementsByTagName("span").length, 1,
-       "A default snippet is visible.");
+       "A default snippet is present.");
   }
 },
 
@@ -60,7 +62,7 @@ let gTests = [
     let snippetsElt = doc.getElementById("snippets");
     ok(snippetsElt, "Found snippets element");
     is(snippetsElt.getElementsByTagName("span").length, 1,
-       "A default snippet is visible.");
+       "A default snippet is present.");
 
     aSnippetsMap.delete("snippets");
   }
@@ -160,6 +162,43 @@ let gTests = [
   }
 },
 
+{
+  desc: "Check snippets map is cleared if cached version is old",
+  setup: function (aSnippetsMap)
+  {
+    aSnippetsMap.set("snippets", "test");
+    aSnippetsMap.set("snippets-cached-version", 0);
+  },
+  run: function (aSnippetsMap)
+  {
+    ok(!aSnippetsMap.has("snippets"), "snippets have been properly cleared");
+    ok(!aSnippetsMap.has("snippets-cached-version"),
+       "cached-version has been properly cleared");
+  }
+},
+
+{
+  desc: "Check cached snippets are shown if cached version is current",
+  setup: function (aSnippetsMap)
+  {
+    aSnippetsMap.set("snippets", "test");
+  },
+  run: function (aSnippetsMap)
+  {
+    let doc = gBrowser.selectedTab.linkedBrowser.contentDocument;
+
+    let snippetsElt = doc.getElementById("snippets");
+    ok(snippetsElt, "Found snippets element");
+    is(snippetsElt.innerHTML, "test", "Cached snippet is present.");
+
+    is(aSnippetsMap.get("snippets"), "test", "snippets still cached");
+    is(aSnippetsMap.get("snippets-cached-version"),
+       AboutHomeUtils.snippetsVersion,
+       "cached-version is correct");
+    ok(aSnippetsMap.has("snippets-last-update"), "last-update still exists");
+  }
+},
+
 ];
 
 function test()
@@ -228,6 +267,7 @@ function promiseSetupSnippetsMap(aTab, aSetupFn)
   cw.ensureSnippetsMapThen(function (aSnippetsMap) {
     // Don't try to update.
     aSnippetsMap.set("snippets-last-update", Date.now());
+    aSnippetsMap.set("snippets-cached-version", AboutHomeUtils.snippetsVersion);
     // Clear snippets.
     aSnippetsMap.delete("snippets");
     aSetupFn(aSnippetsMap);

browser/modules/AboutHomeUtils.jsm

@@ -15,7 +15,9 @@ const SNIPPETS_URL_PREF = "browser.aboutHomeSnippets.updateUrl";
 // Should be bumped up if the snippets content format changes.
 const STARTPAGE_VERSION = 4;
 
-this.AboutHomeUtils = new Object();
+this.AboutHomeUtils = {
+  get snippetsVersion() STARTPAGE_VERSION
+};
 
 /**
  * Returns an object containing the name and searchURL of the original default