I just noticed that my macOS Dock has three icons for Firefox Nightly in the recent-apps section. See attached screenshot.

If I quit Firefox Nightly and remove these three icons, and then start Nightly and quit, then one icon appears there.

If I start+quit Firefox Nightly again, then that one icon disappears (in a macOS "flourish" animation) and is replaced by 3 new ones.

At that point, if I start+quit Firefox Nightly again, then those 3 icons disappear (with the same "flourish") and are replaced by 3 new ones.

The three icons (plus my main pinned icon) all point to the same Firefox Nightly app in my Applications folder (if I right-click them and choose Options|Show-in-Finder).

Filing this as a regression from bug 1667276 at nalexander's suggestion/hunch (though I haven't technically done any mozregression'ing or anything).

Steve Jalim observed the same issue as part of bug 1736373 comment 4, BTW.

I thought the background/headless modes already handled not displaying the dock icon and related animations, but this appears to not be correct: there's a tiny bit of animation as either starts, although the dock icon appears to never be actually displayed. I see this even testing the new environment variable from Bug 1731501, so this may be the best we can do when launching the firefox process.

I can't explain the multiple dock icons at this time. As we dig into Bug 1736373, hopefully we'll have more understanding of how the update process could be causing this.

When you go into about:support , is your update folder pointing to the Applications folder?

Set release status flags based on info from the regressing bug 1667276

(In reply to AmirH [:Amir] from comment #3)

When you go into about:support , is your update folder pointing to the Applications folder?

No, looks like it's not. "Update folder" there says:

/Users/dholbert/Library/Caches/Mozilla/updates/Applications/Firefox Nightly

(In reply to Daniel Holbert [:dholbert] from comment #5)

(In reply to AmirH [:Amir] from comment #3)

When you go into about:support , is your update folder pointing to the Applications folder?

No, looks like it's not. "Update folder" there says:

/Users/dholbert/Library/Caches/Mozilla/updates/Applications/Firefox Nightly

That looks as I expect.

FWIW, I just retested this and can confirm this issue has gone away with current Nightly (which I think matches our expectations, given the rollback patch that landed in bug 1736373 comment 37).

Specifically: I manually removed the three Firefox Nightly icons from my Recent Apps area at the right of my dock; and then I quit Nightly and reopened it, and then quit and reopened it again, for good measure. Nothing (re)appeared in the Recent Apps area.

So this is fixed for now, I think. I'll defer to bholley/nalexander/other-folks-working-on-the-relevant-code on whether it makes sense to close this or leave it open or what.

I'm going to close this, since it's not something to be addressed outside of the interactions with updating and background tasks. Thanks, :dholbert!