Bug 2047962 - Unwrap legacy data:text/plain, pref values in autoconfig. ,Gijs a=pascalc

Original Revision: https://phabricator.services.mozilla.com/D309831

Differential Revision: https://phabricator.services.mozilla.com/D310632

Author: mkaply

extensions/pref/autoconfig/src/prefcalls.js

@@ -37,6 +37,16 @@ function defaultPref(prefName, value) {
   try {
     var prefBranch = Services.prefs.getDefaultBranch(null);
     if (typeof value == "string") {
+      // Unwrap the legacy homepage form that the localizable-pref reader used
+      // to handle (bug 1490339). Match it exactly so we don't touch deliberate
+      // data: URLs.
+      var legacyPrefix = "data:text/plain,browser.startup.homepage=";
+      if (
+        prefName == "browser.startup.homepage" &&
+        value.startsWith(legacyPrefix)
+      ) {
+        value = value.substring(legacyPrefix.length);
+      }
       if (gIsUTF8) {
         prefBranch.setStringPref(prefName, value);
         return;

extensions/pref/autoconfig/test/unit/autoconfig-all.cfg

@@ -6,6 +6,12 @@ pref("_autoconfig_.test.userpref", "userpref");
 // Verify this one has a default pref
 defaultPref("_autoconfig_.test.defaultpref", "defaultpref");
 
+// Verify the legacy homepage data:text/plain, wrapper is unwrapped
+defaultPref("browser.startup.homepage", "data:text/plain,browser.startup.homepage=http://www.example.com/");
+
+// Verify the same wrapper on any other pref is left untouched
+defaultPref("_autoconfig_.test.datapref", "data:text/plain,_autoconfig_.test.datapref=datapref");
+
 // Verify this one is locked
 lockPref("_autoconfig_.test.lockpref", "lockpref");
 

extensions/pref/autoconfig/test/unit/test_autoconfig.js

@@ -42,6 +42,16 @@ function run_test() {
     );
     equal("defaultpref", prefs.getStringPref("_autoconfig_.test.defaultpref"));
 
+    equal(
+      "http://www.example.com/",
+      prefs.getStringPref("browser.startup.homepage")
+    );
+
+    equal(
+      "data:text/plain,_autoconfig_.test.datapref=datapref",
+      prefs.getStringPref("_autoconfig_.test.datapref")
+    );
+
     ok(prefs.prefIsLocked("_autoconfig_.test.lockpref"));
     equal("lockpref", prefs.getStringPref("_autoconfig_.test.lockpref"));