Block Theme Previews: Live preview displays the active theme instead of the chosen theme

[franzaurus]

Description

In WordPress 6.3 beta3, when I do live preview for a selected block theme, the Site Editor displays the active theme instead of the chosen theme.

Step-by-step reproduction instructions

1. Activate TT2 or any other block theme
2. Under Appearance > Themes, click to live preview the TT3 theme
3. Notice that the Site Editor shows you the preview of the active TT2 theme instead of TT3

Screenshots, screen recording, code snippet

Active TT2, live previewing TT3

Environment info

Localwp 7.02+6395
WordPress: 6.3-beta3
PHP: 8.1.9
Server: nginx/1.16.0
Database: mysqli (Server: 8.0.16 / Client: mysqlnd 8.1.9)
Browser: Chrome 114.0.0.0 (Windows 10/11)
Theme: Twenty Twenty-Three 1.1
MU-Plugins: None activated
Plugins:
    WordPress Beta Tester 3.5.0
    WordPress Importer 0.8.1

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

[jordesign]

Thanks for the report @franzaurus !

I've tested this and can confirm I have been able to recreate this. When no page or template is selected - the existing active theme preview is shown. It is only when a specific template or page is shown that the new theme is previewed.

(Please note in this video that I had customised the TT3 theme prior to testing).

Screen.Recording.2023-07-05.at.4.46.35.pm.mov

[carolinan]

I am able to reproduce this, but inconsistently. Were you able to narrow down the exact steps to getting the preview to switch to the selected theme?

[carolinan]

Also reported in https://core.trac.wordpress.org/ticket/58712

[jomonthomaslobo1]

@carolinan

Steps to reproduce:

1. Install a block theme
2. Select the live preview
3. The preview shows the name correctly on the left-hand side but on the right-hand side, the theme is not previewed properly.Selecting Activate won’t change the theme.

[carolinan]

Thank you, I meant what to click on for the preview to change to the correct theme.
@jordesign wrote " It is only when a specific template or page is shown that the new theme is previewed."

For me it is inconsistent.

Activate Twenty Twenty-Three
Go to the themes screen. Select Live Preview of any other block theme. Get redirected to the Site Editor. ✔️
The preview shows Twenty Twenty-Three.
I select Pages. The preview still shows Twenty Twenty-Three.
I select Templates. The preview still shows Twenty Twenty-Three.
Now I select Styles and to my surprise it shows the styles and the preview of the correct theme.
I go back to the templates and it shows the correct theme.
Now I go to the Theme screen again and select Live Preview of a third installed block theme.
This time I don't have to click on anything or do anything. The preview is correct.

So I wonder if it is about timing?

[scruffian]

Fixed here: WordPress/wordpress-develop#4795

[franzaurus]

My experience is closer to @jordesign than to @carolinan. I was consistently redirected to the correct theme whenever a "page", or "template" was chosen. Although activating the selected theme would still showed the existing theme as the active one.

My testing environment via instawp

• WordPress: 6.3-beta3
• PHP: 8.1.20
• Server: Apache/2.4.57 (Ubuntu) mod_fcgid/2.3.9 OpenSSL/1.1.1f
• Database: mysqli (Server: 10.6.14-MariaDB-1:10.6.14+maria~ubu2004 / Client: mysqlnd 8.1.20)
• Browser: Chrome 114.0.0.0 (Windows 10/11)
• Theme: Twenty Twenty-Two 1.4
• MU-Plugins: None activated
• Plugins: WordPress Beta Tester 3.5.0

[carolinan]

Does this need any other Gutenberg changes than #52537?

[scruffian]

@carolinan are you still seeing issues?

[carolinan]

No issues, I was more wondering if this should be closed as completed.

[scruffian]

Yes good point!