Provide comment syntax for templates and template parts

[wprediscovered]

Thanks to all of you for working on this great Free Software project!

I'm trying to add copyright and license information to my theme. I do so using SPDX headers using REUSE tool ​https://reuse.software. This adds information to the .html files using HTML comments (<!-- ... -->).

The Site Editor in WordPress 6.0 doesn't seem able to handle with regular HTML comments in templates and template parts.

On a new theme created using new-empty-theme.php this results in the following index.html page for example:

<!--
SPDX-FileCopyrightText: 2019-2022 WordPress Theme Experiments contributors

SPDX-License-Identifier: GPL-2.0-or-later
-->

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

<!-- wp:query {"queryId":1,"query":{"offset":0,"postType":"post","categoryIds":[],"tagIds":[],"order":"desc","orderBy":"date","author":"","search":"","sticky":""}} -->
<!-- wp:post-template -->
<!-- wp:post-title {"isLink":true} /-->

<!-- wp:post-excerpt /-->
<!-- /wp:post-template -->
<!-- /wp:query -->

It renders just fine, but in the Site Editor these comments of templates and template parts get treated as blocks. This results in an error for each template and page template that has the HTML annotations: "This block has encountered an error and cannot be previewed.'"

Copying the block contents (source code) the resulting output is as follows:

<p><!--
SPDX-FileCopyrightText: 2019-2022 WordPress Theme Experiments contributors

SPDX-License-Identifier: GPL-2.0-or-later
--></p>

So it seems that the comment is treated as a paragraph.

Besides this being valid HTML, I couldn't find anything about a separate comment syntax in the ​https://developer.wordpress.org/themes/block-themes/templates-and-template-parts/ documentation.

I expect the Site Editor to ignore non-wp comments rather than trying to parse them as blocks.

I documented some other experiences with using REUSE on WordPress themes in an issue at the REUSE project: ​https://github.com/fsfe/reuse-tool/issues/537

[manfcarlo]

According to ​your screenshot, the comment is being parsed into a Classic block, which I think is the correct behaviour. I can't see ignoring comments from the parser being an option because special HTML comments such as <!--nextpage--> and <!--more--> need to be handled. The addition of paragraph tags and the error message are not appropriate though and lead me to wonder if the fault lies with TinyMCE.

[manfcarlo]

It looks like this was also reported at ​https://github.com/WordPress/gutenberg/issues/47212 and there is already some discussion happening.