1807048 - Consider introduce a nightly-only pref to allow flipping off ExtensionPermissions rkv backend for debugging purposes

Status: NEW

(WebExtensions :: Storage, task, P3)

Description

[Luca Greco [:rpl] [:luca] [:lgreco]]

As part of investigating Bug 1805427 we caught an issue with how ExtensionPermissions and ExtensionScriptingStore are currently using the kvstore backend (as described in more detail in Bug 1807010), that issue is currently Nightly-only but we are still concerned that it may makes it harder to determine if ExtensionScriptingStore issues reported to us against Nightly may be actually triggered by the issue described in Bug 1807010, and given that disabling the ExtensionPermissions kvstore backend in Nightly does currently require a rebuild it may be harder to investigate the issue when we can't reproduce the issue on our side and only the reporter can consistently reproduce it.

For that reason we are considering to add a Nightly-only pref to make it easier for a reporter to confirm us that the issue they may be experiencing with the ExtensionScriptingStore in Nightly is related to Bug 1807010.

It is very likely that Bug 1646181 patch did initially use an about:config pref to flip the kvstore backend on and off and that it has been changed during the review passes to avoid issues related to a user switching back and forth between the two backends, and experience what would look like as an extension permissions data loss issue (due to the data not being migrated back to the JSON file if switching back from the kvstore backend to the json store backend) and so if we will agree to introduce this pref we should make sure that:

• it can't be used in non nightly channels
• that flipping the pref either requires a browser restart or an extension restart to be effective
• the pref name does possibly make it clear enough that it is meant to be used only for debugging purposes (and so to not expect the data to be migrated in both directions, in particular not from the kvstore back to the json store)

Technically this issue (if we have agreed to proceed) is going to track changes to ExtensionPermissions.jsm, but given that we are interested in it mainly for investigating issues related to ExtensionScriptingStore.jsm, we are adding it as a blocker for the scripting API meta.