1580610 - Preferences.jsm .get() for user-set but no default pref throws NS_ERROR_UNEXPECTED

Status: NEW

(Toolkit :: Preferences, defect, P5)

Description

[Ed Lee :Mardak]

({Preferences} = ChromeUtils.import("resource://gre/modules/Preferences.jsm"));
(new Preferences()).set("foo", 5);
(new Preferences({ defaultBranch: true })).get("foo");

[Exception... "Component returned failure code: 0x8000ffff (NS_ERROR_UNEXPECTED) [nsIPrefBranch.getIntPref]"  nsresult: "0x8000ffff (NS_ERROR_UNEXPECTED)"  location: "JS frame :: resource://gre/modules/Preferences.jsm :: Preferences._get :: line 67"  data: no]

Looks like getPrefType returns a type based on the user set pref, so then it tries to get the value of that type, but there's no actual value on the default pref branch.

Comment 1

[:Gijs (he/him)]

I'd strongly advise against using Preferences.jsm, and in favour of using default values, Services.prefs, and lazy pref getters.

I don't think we'll prioritize fixing this any time soon.

Comment 2

[Ed Lee :Mardak]

Looks like bug 1385952 might be getting rid of activitystream's usage of Preferences.jsm anyway although it might just end up copying over various methods from Preferences.jsm