Happens to me on Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.1b2) Gecko/20081201 Firefox/3.1b2. When I try to call this function, I get: Error: uncaught exception: [Exception... "Component returned failure code: 0x80004001 (NS_ERROR_NOT_IMPLEMENTED) [nsIPrefBranch.resetBranch]" nsresult: "0x80004001 (NS_ERROR_NOT_IMPLEMENTED)" location: "JS frame :: file:///Applications/Internet/Firefox%203.1.app/Contents/MacOS/components/fuelApplication.js :: prefs_reset :: line 1010" data: no] Looking at the documentation, this looks about right, the component doesn't implement the reset call. But, considering that FUEL should fix these issues exactly, I would expect it to work around this limitation and reset the branch in some other way.
Just some notes about this as the problem still exists. Changing the flags as well since this is all platforms and broken on Trunk. = PreferenceBranch = The function resetBranch was never implemented and so raises an error http://mxr.mozilla.org/mozilla-central/source/modules/libpref/src/nsPrefBranch.cpp#503 STEELs PreferenceBranch.reset function calls resetBranch and that's the error you get in comment 0 http://mxr.mozilla.org/mozilla-central/source/toolkit/components/exthelper/extApplication.js#278 = Preference = You can however do a direct call to a pref Application.prefs.get("firstname.lastname@example.org").reset() Because that uses the clearUserPref function http://mxr.mozilla.org/mozilla-central/source/modules/libpref/src/nsPrefBranch.cpp#438 The gotcha is that if the pref doesn't exist or hasn't been modified (is default) means that clearUserPref will raise an error. If this reset() function simply wrapped the clearUserPref call in a try / catch block extensions could call reset without having to worry about it.
Created attachment 425318 [details] [diff] [review] wraps the clearUserPref in a try / catch Here's a quick patch to clear up the issue with Preference.reset throwing an exception back up to the user.
That patch looks fine, but it isn't really related to this bug (reset() throwing on PreferenceBranch objects).