Error when trying to undo pending uninstall of a script

[Ventero]

Steps to reproduce:

1. Go to about:addons
2. Uninstall any script (make sure you have a backup)
3. Click "undo".

Instead of restoring the script, this triggers TypeError: item.onEnabled is not a function on addons4-overlay.js:69.

It looks like when the observer is called after clicking the "undo" button, the element returned by gListView.getListItemForID(addon.id) is still an addon-uninstalled element (see http://mxr.mozilla.org/mozilla-central/source/toolkit/mozapps/extensions/content/extensions.xml#1703), which doesn't have the onEnabled/onDisabled methods.

Simply dropping the call doesn't seem to be enough either, as then trying to cancel the removal of a disabled script leads to the steps described in #1811. I'm not too familiar with the whole addon manager stuff, but I think this is because during the call to uninstall (http://mxr.mozilla.org/mozilla-central/source/toolkit/mozapps/extensions/content/extensions.xml#1476), the manager sets addon.userDisabled = false and keeps the previous state in a wasDisabled attribute - but when cancelling the uninstallation, we never check that attribute, but instead simply assume it's enabled. Not sure why this isn't handled by the addon manager itself though.

[arantius]

Works for me in Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:27.0) Gecko/20100101 Firefox/27.0. Step 3 does what I expect. Nothing ends up in the error console.

[jerone]

Confirmed in "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:29.0) Gecko/20100101 Firefox/29.0".

[Ventero]

Ah, sorry, I knew I forgot something: Mozilla/5.0 (X11; Linux x86_64; rv:28.0) Gecko/20100101 Firefox/28.0

[arantius]

Also WFM in Mozilla/5.0 (X11; Linux x86_64; rv:27.0) Gecko/20100101 Firefox/27.0. Something else is going on, I'm just not sure what.

For those with a confirmed failure, is this in a clean profile? If not, can you please try in one?

[Ventero]

Tried it in a clean profile with only current git HEAD of Greasemonkey installed on Mozilla/5.0 (X11; Linux x86_64; rv:27.0) Gecko/20100101 Firefox/27.0, and I'm able to reproduce the steps in the initial report.

[Ventero]

Can't reproduce this anymore in Mozilla/5.0 (X11; Linux x86_64; rv:30.0) Gecko/20100101 Firefox/30.0, closing.

[Ventero]

Actually, nevermind, I can still reproduce this - but only when uninstalling/restoring an enabled script (which makes sense, as the error occurs when GM tries to re-enable the script). Maybe this was the reason why you had trouble reproducing this, Anthony?