Customizer’s Widget's component should only be loaded when not using a Block Theme

[imath]

Hi,

The BuddyPress plugin has a feature to customize the notification emails it sends when users interact. This feature uses the Customizer from the WP Admin context only.

When the current theme is a Block Theme, previewing/customizing notification emails is generating this Warning notice:
PHP Warning: Attempt to read property "title" on null in /path/to/wordpress.develop/build/wp-includes/class-wp-customize-widgets.php on line 905

After some search into the WP_Customize_Manager class I noticed, although these kind of themes do not use the widgets component all corresponding Customizer controllers were loaded although this was not necessary.

Disabling the Customizer widgets component using the 'customize_loaded_components' filter removed this Warning notice, so I could use this from BuddyPress when these kind of themes are active on sites.

But I believe WordPress should only make the Customizer's widgets component available when the active theme is not a Block theme as BuddyPress might not be the only plugin to use the Customizer even if a Block theme is the active one.

Check the current theme is not a block one before adding the widgets component to the Customizer manager.

See ​https://github.com/buddypress/buddypress/pull/215

Trac ticket: https://core.trac.wordpress.org/ticket/60236

[faisal03]

Test Report

I tested the patch, and it is working as expected. ✅

Before

After

Environment

• OS: macOS
• Localhost Server: Nginx
• PHP: 8.2.1
• WordPress: 6.5.3
• Browser: Chrome
• Theme: TT3

Actual Results

• ✅ The patch is working fine and now the PHP notice is gone.

[sumitbagthariya16]

Test Report ✅

---

I tested the patch, and it is working as expected.

Environment

WordPress: 6.5.3
Theme: Twenty Twenty-Three 1.4
PHP: 8.0.30
Web Server: Nginx 1.20.2
Browser: Chrome
OS: macOS Ventura 13.3

Actual Result

The patch is working fine, no more PHP notices.

[webcommsat]

Tested this patch with a colleague, and no PHP notices received in either test.

OS: Mac OS
Localhost Server: Nginx 1.25
PHP: 8.2
WordPress: 6.5.3
Browser: Chrome
Theme: Twenty-twenty three

[audrasjb]

Self assigning for commit.

[audrasjb]

In 58376:

Customize: Avoid loading the widgets component if a block theme is activated.

This changeset adds a check to ensure the current theme is not a block theme before adding the widgets component to the Customizer manager. This avoids a PHP warning when previewing/customizing notification emails with a block theme in BuddyPress and potentially on other plugins.

See ​https://github.com/buddypress/buddypress/pull/215.

Props imath, mukesh27, faisal03, sumitbagthariya16, webcommsat.
Fixes #60236.

committed in https://core.trac.wordpress.org/changeset/58376