Template Part block should not be available in the Post Editor inserter

[priethor]

Description

As of 10.4-RC1, Template Part blocks can be added to the Post Editor in the same way reusable blocks can be added. However, template parts can only be created from the Site Editor.

This issue is related to #30669, which presents the opposite logic for reusable blocks. Original discussion in #30308

Step-by-step reproduction instructions

1. Go to 'Site Editor'
2. Select any block and click on "Make template part"
3. Go to the Post Editor.
4. Open the inserter and look for the recently created template part.

Expected behaviour

Template parts should only be available to insert in template editors.

Actual behaviour

Template parts can be inserted in posts or pages.

WordPress information

• WordPress version: 5.7
• Gutenberg version: 10.4-RC1
• Are all plugins except Gutenberg deactivated? Yes
• Theme used? TT1 Blocks

[carlomanf]

There is nothing on a strictly functional level that prevents a template part from working inside a post or page content. It's more a question of protocol, and while most would agree it's a good protocol to leave template parts out of post or page content, that should be left to site administrators to decide. Would there then be a filter or similar that could bring back template parts to the post inserter if someone wanted to do so?

[priethor]

Thanks for chiming in! Adding a filter is an interesting approach, although I'm wondering what could be a benefit of adding template parts to posts and pages rather than using reusable blocks, as the latter can be created directly from the post editor, are meant to contain content, and belong to the post context. Template parts are created from the site editor and template editors, more geared towards defining the structure and layout of the site itself rather than the content, and are not semantically meant to be added to the posts themselves (to post templates yes).

Could you provide any use-case that would benefit from using template parts rather than reusable blocks, if you happen to have one in mind? I can't seem to come up with one myself.

[carlomanf]

To clarify, I'm not envisioning an ad-hoc filter specifically for this block, but some kind of universal system that controls the block inserter for the different contexts.

There have been many cases where it's been deemed that a given block should only appear in the inserter in certain context(s). This could be within another block (e.g. Column only inside Columns), or it could be only in certain editors, or it could be only in certain post types, or it could be only for certain user capabilities, or it could be the negation/conjunction/disjunction of any of the above.

In this case, I assume you're talking about restricting this block to only be available for a particular post type (i.e. wp_template) but it's the same kind of idea as Column only being available inside Columns, for instance.

However, it seems that there has not been a consistent approach to the implementing restrictions like these. In some cases, it's been done by de-registering the entire block type. In other cases, it's been done by just hiding it from the inserter but allowing the block to be added using code view.

Would it not make sense to do all of this through a centralised system, to increase consistency while also allowing site administrators to modify the configuration through a filter if they want to? It would also make it trivial to solve this issue, rather than spend days discussing the best way to implement it.

[youknowriad]

Template part block is not part of 5.8, that said, we still need a long term solution for this. I'm removing this from the 5.8 board.