Allow child themes to use template parts from parent themes in Full Screen Editor

[catacaustic]

Creating template parts in a theme for the Full Site Editor does not allow template parts from a parent theme to be used by a child theme. These will show when editing a template, and allow you to insert/update/delete them when editing templates, but an error message shows on the public-facing page - "Template part has been deleted or is unavailable: *template-name*".

All that is needed is an additional check if a child theme is active and if so check against the parent theme as well as the child theme.

[catacaustic]

Diff file

[catacaustic]

Sorry, missed which file this applies to -

wp-includes\blocks\template-part.php

[ironprogrammer]

Welcome back to Trac, @catacaustic, and thanks for the report!

This issue looks similar to ​https://github.com/WordPress/gutenberg/issues/44243, where a workaround was to remove the theme name from <!-- wp:template-part -->. For instance, change:

<!-- wp:template-part {"slug":"header","tagName":"header","theme":"my-theme"} /-->

to

<!-- wp:template-part {"slug":"header","tagName":"header"} /-->

Would you mind testing to see if this also fixes the errors you're seeing? Your proposed patch may offer a solution there as well. Thank you!

[poena]

I am not able to reproduce it using WordPress 6.6 RC2.
I am able to insert the parent theme template parts in the Site Editor without editing any code manually, and they work in the editors and the front.

I recommend closing this as fixed.

[ironprogrammer]

I am also unable to reproduce an error against trunk (6.7-alpha-58576-src) with a TT4 child theme using prebuilt templates. In my tests the parent templates are available to the child theme, and when assigned no error occurred on the frontend. (Also noting here that custom templates created for the parent are not visible to the child theme in the site editor, in case this was a nuance of the original report.)

I'm marking this closed, but if the issue remains and some additional context can be provided to reproduce the error, please feel free to reopen the ticket for further investigation.