1521421 - Uninstalling an extension that is also present in another install location should act as upgrade/downgrade

Status: UNCONFIRMED

(Toolkit :: Add-ons Manager, defect, P3)

Description

[YF (Yang)]

If there is already a duplicate bugs, mark it, this issue seems to have a long history.

STR:

1. Install an add-on from http://addons.mozilla.org/.
2. Make some changes to the storage of the add-on.
3. Load its xpi or source code from local via about:debugging#addons for debugging.
4. When you're done debugging or need to go back to the original, choose to 'Remove' the add-on via about:debugging#addons.

Actual results:
After you complete step four, you see the original add-on version, but its storage has been accidentally emptied and there is no way to retrieve it.
If you choose to close or restart the browser, the add-on storage is preserved and the temporarily loaded add-on is dumped.

Expected results:
Restore the previous storage (if any) when removing a temporarily loaded add-on. Although debugging with a daily profile is undesirable, it can happen and unexpected data loss should not be. Or at least, provide a data removal warning if it is an overlay loaded add-on.

Comment 1

[Andrew Swan [:aswan]]

The problem is basically here:
https://searchfox.org/mozilla-central/rev/9eb30227b21e0aa40d51d9f9b08bb0b113c5fadb/toolkit/mozapps/extensions/internal/XPIInstall.jsm#3852-3864

When uninstalling an extension from one location reveals the same extension in a different location, we handle this as an uninstall followed by an install. This is inconsistent with the install logic (which is unfortunately duplicated in a few places) which treats installing an existing extension in a new location as an upgrade (or downgrade). I think the best course here is to change the uninstall process to treat this scenario as an upgrade/downgrade.