Nightly 78.0a1 (2020-05-29) (64-Bit)
macOS 10.15.5

STR:

1.) Enable Top Sites on your NTP
2.) Open a NTP
3.) Click on the Top Sites icon / Triangle above the Top Sites

Expected: Top Sites area should collapse.
Actual: Top Sites area does not collapse.

This is a recent regression.

Looks like the section id changed for top sites feed but not for the content?

https://searchfox.org/mozilla-central/rev/8827278483c337667cdfb238112eb1be397dd102/browser/components/newtab/lib/TopSitesFeed.jsm#834-836

[Tracking Requested - why for this release]:
Easy-to-fix but annoying regression resulting from a 77 patch: bug 1634279.

[Tracking Requested - why for this release]:
Sorry, I meant 78 :)

Just a question: I haven't mentioned that in my bugreport, but when you click on the triangle to try to collapse the Top Sites sections, the collapse does not work AND the tiles are no longer clickable. Will the "not clickable" issue also be fixed with your patch?

Yes, my patch should fix that issue.

(In reply to Harry Twyford [:harry] from comment #7)

Yes, my patch should fix that issue.

Thanks for your feedback :)

https://hg.mozilla.org/mozilla-central/rev/a9abdda8e7f7

The patch landed in nightly and beta is affected.
:harry, is this bug important enough to require an uplift?
If not please set status_beta to wontfix.

For more information, please visit auto_nag documentation.

Comment on attachment 9153141 [details]
Bug 1642082 - Restore the ability to collapse the NTP Top Sites section. r?thecount!

Beta/Release Uplift Approval Request

• User impact if declined: Regression where the Top Sites section on the NTP can't be collapsed.
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): Very small (2-line) change that's baked on Nightly for a few days and that only affects the front-end. If something goes wrong with this patch, it would be easy to undo.
• String changes made/needed:

Comment on attachment 9153141 [details]
Bug 1642082 - Restore the ability to collapse the NTP Top Sites section. r?thecount!

regression fix for new tab, approved for 78.0b3

https://hg.mozilla.org/releases/mozilla-beta/rev/89e06826afe1

I have verified the following, using Firefox Beta 78.0b3 (Build ID: 20200604213430), and Firefox Nightly 79.0a1 (Build ID: 20200605043926) on Windows 10 x64, macOS 10.15, and Ubuntu Linux 18.04:

• The "Top Sites" section is collapsed when the title is clicked.
• The "Top Sites" section is expanded when the title is clicked again.
• The "Top Sites" section is collapsed when the "Collapse Section" option is selected from the "Section Context Menu" (...).
• The "Top Sites" section is expanded when the "Expand Section" option is selected from the "Section Context Menu" (...).
• The "Top Sites" tiles can be clicked after the "Top Sites" section is expanded.