1424161 - Synced tabs sidebar is blank even if turn on tab syncing

Status: NEW

(Firefox :: Sync, defect, P5)

Description

[magicp]

Attachment: synced-tabs-sidebar-is-blank.mp4

Steps to reproduce:
1. Launch the latest Nightly
2. Sign in and turn off "Open tabs" in about:preferences#sync
3. Run sync
4. Show synced tabs sidebar > "Turn on tab syncing to view..." and [Open Sync Preferences] button will be shown
5. Click [Open Sync Preferences] button
6. Turn on "Open tabs" in Preferences

Actual Results:
Synced tabs sidebar is blank until next sync or you switch sidebar.

Expected Results:
Shows "Want to see your tabs from other devices here?" and [Connect Another Device] button when turn on tab syncing.

Comment 1

[Edouard Oger [:eoger]]

Attachment: Bug 1424161 - Track hasSyncedThisSession properly in SyncedTabs.jsm.

Review commit: https://reviewboard.mozilla.org/r/216990/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/216990/

Comment 2

[Mark Hammond [:markh] [:mhammond]]

Comment on attachment 8947233 [details]
Bug 1424161 - Track hasSyncedThisSession properly in SyncedTabs.jsm.

https://reviewboard.mozilla.org/r/216990/#review222878

I'm not too keen on this change (although I'm not sure what I would be keen on :/)

IIUC, this change will make hasSyncedThisSession on the tabs engine redundant - it will never be true that the engine will have true when the service has false. So if we do go this route, then the attribute on the tabs engine should die.

What also makes this complicated is the UX decision that when we know that we are yet to discover if tabs are available, then both the sidebar and the panel show an empty UI. So the bug as reported is actually consistent with the browser as it starts - but the big difference between showing it at startup vs in this STR is that at startup we force a sync (hoping the blank state resolves quickly) vs in this STR where we need to wait for the next scheduled sync.

I wonder if a better option might be to just force an engine-specific sync when an engine is enabled via prefs?

Comment 3

[Mark Hammond [:markh] [:mhammond]]

I also meant to mention: there are some places where we do a partial sync, such as https://searchfox.org/mozilla-central/rev/f41017f5cd7b5f3835d282fbe011d2899574fc2b/browser/base/content/browser-pageActions.js#1015, which looks like would cause problems with this patch as the module would indicate we have synced tabs when we haven't but will soon.