1703072 - Restored pinned tabs discarded status always false

Status: NEW

(WebExtensions :: Frontend, defect, P3)

Description

[mesvam]

Attachment: pinned discarded tabs API test.xpi

To reproduce

• Turn on "Restore previous session" in options
• set browser.sessionstore.restore_pinned_tabs_on_demand = true in about:config
• Open a webpage and pin that tab
• Open another tab and focus on new tab. The pinned tab should be in the background
• Close and reopen Firefox
• Open browser console and check "Show Content Messages" under gear icon
• Install test extension and click icon. A number will be logged to console, indicating the number of pinned tabs which are discarded reported by browser.tabs.query({pinned: true, discarded: true})
• Focus the pinned tab to confirm it's discarded. The pinned tab should load when clicked on, and should not be already loaded.

Results:
The pinned tab is not loaded on startup, yet the API reports 0 pinned and discarded tabs

Expected:
Should find at least 1 pinned discarded tab

Comment 1

[Alex Cornestean]

Hello,

I reproduced the issue on the latest Nightly (89.0a1/20210406152948), Beta (88.0b8/20210406185740) and Release (87.0/20210318103112) under Windows 10 x64 and Ubuntu 16.04 LTS.

As per the description, the value 0 (zero) is logged in the console. The pinned tab is discarded and clicking on it will start reloading it.

Comment 2

[Rob Wu [:robwu]]

I'm going to investigate this when I have somewhat more time. Since this is non-standard behavior behind a pref, this doesn't have a high priority.

Comment 4

[anon]

It's possible fixing this bug may fix https://bugzilla.mozilla.org/show_bug.cgi?id=1853047 ( unloaded pinned tabs still spawn a process when pref browser.sessionstore.restore_pinned_tabs_on_demand is true ).

When browser.sessionstore.restore_on_demand is false, all the non-pinned tabs spawn a process when a window is restored (though tabs with same domain may fall under one process), even before Firefox loads them through its progressive loading algorithm (3 tabs at a time). However, if browser.sessionstore.restore_on_demand is true, the tabs are correctly set as discarded and no processes spawn for them.

With a horizontal tab bar, having too many pinned tabs is problematic. They can take up too much space or actually fill the whole tab bar with no way to scroll to the right to view overflowing tabs ( https://bugzilla.mozilla.org/show_bug.cgi?id=583299 ). However, with native vertical tabs and a wide screen monitor, numerous pinned tabs may be added with little drawback. When a user has lots of pinned tabs, they may prefer to keep them discarded and set browser.sessionstore.restore_pinned_tabs_on_demand to true.