Check if a Firefox 3.5 add-on is enabled

Question

In order inform the user of possible conflicts, I'd like to have my add-on check if another add-on is installed and enabled. If so, I can disable either it or my own at the user's bequest:

function disableExtension(id) {
    var man = Components.classes["@mozilla.org/extensions/manager;1"];
    if (man) {
        man = man.getService(Components.interfaces.nsIExtensionManager);
    }
    if (man) {
        man.disableItem(id);
    } else {
        Components.utils.import("resource://gre/modules/AddonManager.jsm");
        AddonManager.getAddonByID(id, function(addon) {
            addon.userDisabled = true;
        });
    }
}

But I first, of course have to check if a certain other add-on is installed. Presently, I do this as follows:

if (Application.extensions) {
    // Gecko 1.9.2 and older
    ext = Application.extensions.get(id);
    if (ext) {
        // TODO check if extension is also enabled
        disableExtension(id);
    }
} else {
    // Gecko 2.0.0 and newer
    Application.getExtensions(function(extensions) {
        ext = extensions.get(id);
        Components.utils.import("resource://gre/modules/AddonManager.jsm");
        AddonManager.getAddonByID(id, function(addon) {
            if (!addon.userDisabled) {
                disableExtension(id);
            }
        });
    })
}

The code for Firefox 4 (the else-statement) works fine. For older versions of Firefox (3.5 and older), I can't for the life of me figure out how to determine if the extension is in fact installed.

Does anybody know how to do this?

The only thing that comes to mind is running through `extensions.ini` and looking for the extension's `getInstallLocation()`, but I don't like that approach at all. — Paul Lammertsma, Nov 28 '10 at 03:29

Paul Lammertsma · Accepted Answer · 2010-12-02T00:04:50.517

The answer was trivial; I had overlooked the enabled attribute for extIExtension.

I resolved it as follows:

var ext;
if (typeof Application != 'undefined') {
    if (Application.extensions) {
        // Gecko 1.9.0 - 1.9.2
        ext = Application.extensions.get(id);
        if (ext) {
            if (ext.enabled) disableExtension(id);
        }
    } else {
        // Gecko 2.0.0 and newer
        Application.getExtensions(function(extensions) {
            ext = extensions.get(id);
            Components.utils.import("resource://gre/modules/AddonManager.jsm");
            AddonManager.getAddonByID(id, function(addon) {
                if (!addon.userDisabled) {
                    disableExtension(id);
                }
            });
        })
    }
} else {
    // Gecko 1.8.0
    var extMgr = Cc["@mozilla.org/extensions/manager;1"].getService(Ci.nsIExtensionManager);
    if (extMgr) {
        ext = extMgr.getItemForID(id);
    }
    var extMgrDs = extMgr.datasource;
    if (extMgrDs) {
        var rdfSvc = Cc["@mozilla.org/rdf/rdf-service;1"].getService(Ci.nsIRDFService);
        if (rdfSvc && ext) {
            var source = rdfSvc.GetResource("urn:mozilla:item:" + ext.id);
            var property = rdfSvc.GetResource("http://www.mozilla.org/2004/em-rdf#isDisabled");
            var target = rdfSvc.GetLiteral("true");
            var disabled = extMgrDs.HasAssertion(source, property, target, true);
            if (!disabled) {
                disableExtension(id);
            }
        }
    } else if (typeof className != "undefined") {
        // Opens the add-on window
        BrowserOpenAddonsMgr();
    }
}

Where disableExtension() is:

disableExtension: function(id) {
    var man = Components.classes["@mozilla.org/extensions/manager;1"];
    if (man) {
        man = man.getService(Components.interfaces.nsIExtensionManager);
    }
    if (man) {
        man.disableItem(id);
        restart();
    } else {
        Components.utils.import("resource://gre/modules/AddonManager.jsm");
        AddonManager.getAddonByID(id, function(addon) {
            addon.userDisabled = true;
            restart();
        });
    }
}

And restart() is:

restart: function() {
    var appStartup = Components.classes["@mozilla.org/toolkit/app-startup;1"];
    if (appStartup) {
        appStartup = appStartup.getService(Components.interfaces.nsIAppStartup);
    }
    if (appStartup) {
        appStartup.quit(appStartup.eAttemptQuit | appStartup.eRestart);
    } else if (typeof Application != 'undefined') {
        if (Application.restart) Application.restart();
    }
}

This hasn't been tested on Firefox 1.0-1.5, but works on:

Firefox 4.0b7
Firefox 3.6
Firefox 3.5
Firefox 3.0
Firefox 2.0

Credit for helping me out goes to Atte Kemppilä.

Incidentally, I don't recommend disabling add-ons and restarting Firefox without the user's consent. The above code is simplified, and in my add-on I use notifications to guide the user through these steps. — Paul Lammertsma, Dec 02 '10 at 00:06

score 2 · Answer 2 · answered Feb 24 '11 at 09:43

Very informative write-up.
Note that you can use the "enabled" attribute for Gecko 2 as well. This makes the code somewhat simpler.

   if (Application.extensions) {
        // Gecko 1.9.0 - 1.9.2
        ext = Application.extensions.get(id);
        if (ext) {
            if (ext.enabled) disableExtension(id);
        }
    } else {
        // Gecko 2.0.0 and newer
        Application.getExtensions(function(extensions) {
            ext = extensions.get(id);
            if (ext.enabled) disableExtension(id);
        });
    }

For best practice you can of course move the repeated code to an external function.

I haven't tried this, but it seems likely to work as Mozilla is pretty good at keeping backwards-compatibility. I'll give it a shot when I have the opportunity and post the results. — Paul Lammertsma, Feb 24 '11 at 18:57

Check if a Firefox 3.5 add-on is enabled

2 Answers2