Bug 448741 - "nsISessionStore uses private methods and is not extensible" [r=dietrich]

browser/components/sessionstore/src/nsSessionStartup.js

@@ -108,7 +108,7 @@ SessionStartup.prototype = {
     var resumeFromCrash = this._prefBranch.getBoolPref("sessionstore.resume_from_crash");
     if ((resumeFromCrash || this._doResumeSession()) && this._sessionFile.exists()) {
       // get string containing session state
-      this._iniString = this._readFile(this._sessionFile);
+      this._iniString = this._readStateFile(this._sessionFile);
       if (this._iniString) {
         try {
           // parse the session state into JS objects
@@ -322,6 +322,25 @@ SessionStartup.prototype = {
 
 /* ........ Storage API .............. */
 
+  /**
+   * Reads a session state file into a string and lets
+   * observers modify the state before it's being used
+   *
+   * @param aFile is any nsIFile
+   * @returns a session state string
+   */
+  _readStateFile: function sss_readStateFile(aFile) {
+    var stateString = Cc["@mozilla.org/supports-string;1"].
+                        createInstance(Ci.nsISupportsString);
+    stateString.data = this._readFile(aFile) || "";
+    
+    var observerService = Cc["@mozilla.org/observer-service;1"].
+                          getService(Ci.nsIObserverService);
+    observerService.notifyObservers(stateString, "sessionstore-state-read", "");
+    
+    return stateString.data;
+  },
+
   /**
    * reads a file into a string
    * @param aFile

browser/components/sessionstore/src/nsSessionStore.js

@@ -1897,7 +1897,19 @@ SessionStoreService.prototype = {
     this._dirty = aUpdateAll;
     var oState = this._getCurrentState();
     oState.session = { state: ((this._loadState == STATE_RUNNING) ? STATE_RUNNING_STR : STATE_STOPPED_STR) };
-    this._writeFile(this._sessionFile, oState.toSource());
+    
+    var stateString = Cc["@mozilla.org/supports-string;1"].
+                        createInstance(Ci.nsISupportsString);
+    stateString.data = oState.toSource();
+    
+    var observerService = Cc["@mozilla.org/observer-service;1"].
+                          getService(Ci.nsIObserverService);
+    observerService.notifyObservers(stateString, "sessionstore-state-write", "");
+    
+    // don't touch the file if an observer has deleted all state data
+    if (stateString.data)
+      this._writeFile(this._sessionFile, stateString.data);
+    
     this._lastSaveTime = Date.now();
   },
 

browser/components/sessionstore/test/browser/Makefile.in

@@ -46,6 +46,7 @@ include $(topsrcdir)/config/rules.mk
 
 _BROWSER_TEST_FILES = \
 	browser_367052.js \
+	browser_448741.js \
 	$(NULL)
 
 libs:: $(_BROWSER_TEST_FILES)

browser/components/sessionstore/test/browser/browser_448741.js

@@ -0,0 +1,96 @@
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is sessionstore test code.
+ *
+ * The Initial Developer of the Original Code is
+ * Simon Bünzli <zeniko@gmail.com>.
+ * Portions created by the Initial Developer are Copyright (C) 2008
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+function test() {
+  /** Test for Bug 448741 **/
+  
+  // test setup
+  let ss = Cc["@mozilla.org/browser/sessionstore;1"].getService(Ci.nsISessionStore);
+  let os = Cc["@mozilla.org/observer-service;1"].getService(Ci.nsIObserverService);
+  let tabbrowser = getBrowser();
+  waitForExplicitFinish();
+  
+  let uniqueName = "bug 448741";
+  let uniqueValue = "as good as unique: " + Date.now();
+  
+  // set a unique value on a new, blank tab
+  var tab = tabbrowser.addTab();
+  ss.setTabValue(tab, uniqueName, uniqueValue);
+  let valueWasCleaned = false;
+  
+  // prevent our value from being written to disk
+  let cleaningObserver = {
+    observe: function(aSubject, aTopic, aData) {
+      ok(aTopic == "sessionstore-state-write", "observed correct topic?");
+      ok(aSubject instanceof Ci.nsISupportsString, "subject is a string?");
+      ok(aSubject.data.indexOf(uniqueValue) > -1, "data contains our value?");
+      
+      // find the data for the newly added tab and delete it
+      let state = eval(aSubject.data);
+      for each (let winData in state.windows) {
+        for each (let tabData in winData.tabs) {
+          if (tabData.extData && uniqueName in tabData.extData &&
+              tabData.extData[uniqueName] == uniqueValue) {
+            delete tabData.extData[uniqueName];
+            valueWasCleaned = true;
+          }
+        }
+      }
+      
+      ok(valueWasCleaned, "found and removed the specific tab value");
+      aSubject.data = uneval(state);
+      os.removeObserver(this, aTopic, false);
+    }
+  };
+  
+  // make sure that all later observers don't see that value any longer
+  let checkingObserver = {
+    observe: function(aSubject, aTopic, aData) {
+      ok(valueWasCleaned && aSubject instanceof Ci.nsISupportsString,
+         "ready to check the cleaned state?");
+      ok(aSubject.data.indexOf(uniqueValue) == -1, "data no longer contains our value?");
+      
+      // clean up
+      tabbrowser.removeTab(tab);
+      os.removeObserver(this, aTopic, false);
+      finish();
+    }
+  };
+  
+  // last added observers are invoked first
+  os.addObserver(checkingObserver, "sessionstore-state-write", false);
+  os.addObserver(cleaningObserver, "sessionstore-state-write", false);
+}