1492838 - Firefox breaks after removing/undoing a deleted language pack in the same session

Status: RESOLVED WONTFIX

(Toolkit :: Add-ons Manager, defect)

Description

[Emil Ghitta, QA [:emilghitta]]

Attachment: LanguagePack.gif

[Affected versions]:
Firefox 64.0a1 (BuildId:20180919220108)
Firefox 63.0b7 (BuildId:20180917143811)
Firefox 62.0 (BuildId:20180830143136)

[Unaffected versions]:
Firefox 60.2.0esr (BuildId:20180903060751)

[Affected platforms]:
Windows 10 64bit.
Windows 10 32bit.
Ubuntu 16.04 64bit.
macOS 10.13.6

[Preconditions]
1. Launch Firefox.
2. Install a language pack xpi.
3. Create the intl.locale.requested pref and have it set with what locale you have installed.
4. Restart Firefox.

[Steps to reproduce]:
1. Access the profile path and delete the xpi from the extensions folder (While Firefox is open). DON'T restart Firefox.
2. Access the about:addons page.
3. Remove the language pack (via the Remove button).
4. Click the "Undo" button.
5. Access any about page.

[Expected result]:
The about pages are displayed successfully.

[Actual result]:
The about pages become unusable.

[Regression Range]:
I will get back with a regression range asap.

[Additional Notes]
- For further information regarding this issue please observe the attached screencast.

Comment 1

[Emil Ghitta, QA [:emilghitta]]

Attachment: Close Firefox.gif

I have encountered another scenario, which seems to be worse. 
On some locales (ex ff), while this issue is encountered, Firefox is not closeable.
I managed to reproduce this scenario by disabling/enabling the xpi from about:addons (instead of remove/undo from steps 3 and 4) and then pressing the X button or trying to quit Firefox via the Hamburger menu.

Comment 2

[David Durst [:ddurst]]

Closing this as that's a pretty edgy edge case (the remove and undo remove part).