Export: Getting `Template part has been deleted or is unavailable: header` after uploading to a new site

[oskosk]

While working on a theme created from scratch with Create Block Theme I opted to export the theme using the Export the activated theme with user changes option:

I got a zip bundle and uploaded to another site. On that new site I visited the editor and was shown a message Template part has been deleted or is unavailable: header (footer as well).

Workaround

I noticed then that the templates/index.html file part of the bundle created by the export was referring to the header part like this:

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

... while my original file (the one generated from scratch) read:

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

After removing "theme":"new blank theme" the template worked properly loading the index part.

How to reproduce

1. On a fresh site, install Create Block Theme
2. Visit Appearance -> Create Block Theme
3. Create a blank theme. Name it Le Theme.
4. Activate the Theme in Appearance -> Themes
5. Export the theme: Visit Appearance -> Create Block Theme and export the theme. Keep the downloaded bundle somewhere.
6. Deactivate and delete the recently created theme Le Theme: Visit Appearance -> Create Block Theme, switch to Twenty Twenty-Three, then delete Le Theme.
7. Upload and activate the downloaded zip from step 5.
8. Visit the Editor.
9. Confirm the part is missing. Expect to see Template part has been deleted or is unavailable: header and Template part has been deleted or is unavailable: footer messages.

[oskosk]

Seems like during the process of exporting, the theme attribute is first removed here

create-block-theme/admin/class-create-block-theme-admin.php

Lines 992 to 993 in 031eee5

	function add_templates_to_zip( $zip, $export_type, $new_slug ) {
	$theme_templates = $this->get_theme_templates( $export_type, $new_slug );

eventually calling _remove_theme_attribute_in_block_template_content here:

create-block-theme/admin/class-create-block-theme-admin.php

Line 497 in 031eee5

$template->content = _remove_theme_attribute_in_block_template_content( $template->content );

...and then added back here

create-block-theme/admin/class-create-block-theme-admin.php

Line 1004 in 031eee5

$template_data = $this->make_template_images_local( $template );

via

create-block-theme/admin/class-create-block-theme-admin.php

Lines 732 to 734 in 031eee5

	case 'core/template-part':
	$block = $this->add_theme_attr_to_template_part_block( $block );
	break;

This behavior was introduced in 1.6 with 6f00002 as part of #213

[matiasbenedetto]

Thanks, @oskosk for the detailed description of the problem.
It seems like we are adding the theme key to the template part block in all the cases and it's only needed in some of them.
I'll submit a potential fix shortly.

[Retrofitterdk]

I’ve experienced this problem as well. It only seems to happen, when theme name is multiple words. Shortening theme name to one word fixed the problem.

[matiasbenedetto]

This behavior was introduced in 1.6 with 6f00002 as part of #213

The problem is related to the fact that the characters used in the theme slug were not sanitized correctly, specifically the white spaces. That problem is pre-existent with those changes. Anyways is a good opportunity to fix this bug and simplify the code a little. A potential fix: #244

[oskosk]

Alright , thanks!
Note that after reporting this issue I continued working with 1.5.1 the whole day without experiencing the issue. Also with a theme using a name with spaces

[matiasbenedetto]

Note that after reporting this issue I continued working with 1.5.1 the whole day without experiencing the issue. Also with a theme using a name with spaces

Yep, but that's because in 1.5.1 in we remove the theme key in the template parts linked from templates. In 1.6.0 no, so the template parts were linked like this (following your example theme name): "theme":"le theme" instead of "theme":"letheme"

[Thelmachido]

The same seems to happen when you try to create a clone of the TT3 theme, this was reported on this Forum review:

Thanks, @matiasbenedetto for looking into this.

[Thelmachido]

More reports from the Create Block Theme forum: https://wordpress.org/support/topic/bug-exporting-templates-uses-wrong-theme-key/

[matiasbenedetto]

The fix (#244) was merged and released in version 1.6.1 of the plugin. It should be working as expected now.

[oskosk]

Thank so much @matiasbenedetto

[ya123123]

Hello, @matiasbenedetto
This issue was fixed in 1.6.1, but it seems to happen again in 1.6.2.

I faced the same issue when I export, clone, overwrite the TT3 theme.

[matiasbenedetto]

This recent refactor #237 wiped out the fix added in #244, that's the reason for this issue happening again in 1.6.2.
I'm adding again the changes from #244 to #259.