Block preview when adding a block is not working in WordPress 5.6.1

[blankart]

Description

Block preview when adding a block is not working in WordPress 5.6.1

Step-by-step reproduction instructions

Click the "add block" button. Hover one of the block entry buttons.

Expected behaviour

A popover with block preview should be visible

Actual behaviour

The popover is not visible

Screenshots or screen recording (optional)

WordPress information

• WordPress version: 5.6.1
• Gutenberg version: Not installed
• Are all plugins except Gutenberg deactivated? Yes
• Are you using a default theme (e.g. Twenty Twenty-One)? Yes

Device information

• Device: Desktop
• Operating system: MacOS Big Sur
• Browser: Chrome

[paaljoachim]

Thank you for the report @blankart

Testing.
Theme: Twenty Twenty One.
WordPress version: 5.6.1
No plugins activated.
Chrome
Mac OSX 10.15.7 (Catalina)

I open an existing page (draft).

Twenty Nineteen and Twenty Twenty theme also contains the same lack of block preview error.
The same as with TT1 theme.
Tested with estar theme. Same error.

---

Activating the Gutenberg plugin 9.9.1 the Block preview works.

---

Testing 5.6 version of WordPress.
No plugins activated.

Block preview works in 5.6.

---

My conclusion is that the 5.6.1 update has caused an error so that Block previews are not seen.

@noisysocks Robert.

[noisysocks]

@paaljoachim: Could you confirm if this happens in 5.7 beta 1?

[paaljoachim]

Good call, Robert!
@noisysocks

Testing.
Theme: Twenty Twenty One.
WordPress version: 5.7 beta 1
Only the WordPress Beta Tester plugin is activated.
Chrome
Mac OSX 10.15.7 (Catalina)

Opening Sample Page. Changed it to a draft.
Block previews work fine in 5.7 beta 1.

Tested:
Existing page and post.
New page and post.
Draft page and post.
Block preview works nicely.

[tobiasger]

I'm having the same issue with Wordpress Version 5.6.1.

[bobbingwide]

Ditto. But shouldn't there be a TRAC issue since this problem occurs when Gutenberg is not activated.

[paaljoachim]

Hi Riad and Greg. I am just informing you about this issue.

@youknowriad @gziolo

[youknowriad]

Do we know if there will be a 5.6.2 before 5.7. It's not clear at this point? and this is already fixed ini 5.7 so.
It would also be good to try to find what fixed this issue.

[paaljoachim]

There are talks about a 5.6.2 release before the release of 5.7.
I asked in core for an official P2 post about the update.

[desrosj]

I'm working on preparing a 5.6.2 RC, and hoping to get that out at some point today (the 16th). Has anyone been able to locate the change that fixed this issue? I'll take a look, but without being able to find that, we may have to skip this one in 5.6.2.

[ockham]

@desrosj The wp/5.6 branch has a list of commits that should allow narrowing the search down (as to what broke block preview). Given the release dates of WP 5.6.1 (Feb 3) and 5.6.0 (Dec 8), I believe that that commit must be one of the top 8 ones that were apparently cherry-picked on Jan 28.

[ockham]

#26432 seems like a likely candidate; #26583's PR desc says

The fix in #26432 accidentally broke block previews in the Inserter due to a naïve use of overflow: hidden to fix the overscroll with the block library open in the site editor.

While it only refers to the site editor (and not the post editor), the files that it touches seem editor agnostic.

cc/ @mattwiebe for confirmation 😊

Maybe someone (@desrosj or @paaljoachim? 🙏 ) could give this a try. (It's a bit late here, I'm already after hours 😉 )

[desrosj]

Thanks for the assist, @ockham! #26583 does indeed restore block previews in the 5.6 branch! I've gone ahead and added that to #29042.

[tellthemachines]

I just tested #26583 on the 5.6 branch and it works well, though I see @desrosj beat me to it 😄

[ockham]

Filed #29073 to request an e2e test for block preview visibility.

[desrosj]

This was merged in #29058 and will be shipped in the upcoming 5.6.2.

[mattwiebe]

While it only refers to the site editor (and not the post editor), the files that it touches seem editor agnostic

Yes, you are correct, this touched the interface skeleton that is used to construct both post and site editors.