"Insert Before/After" menu options disappear if paragraph block is hidden from inserter

[cbirdsong]

Description

The "Insert Before/After" items in the block options menu disappear when the paragraph block is disabled.

Step-by-step reproduction instructions

1. Click on the three vertical dots menu in the top right.
2. Click "Preferences"
3. Click "Blocks"
4. Uncheck "Paragraph"

or

1. Register a Javascript file that runs in the editor.
2. Inside it, use hideBlockTypes to hide the paragraph block.

Screenshots, screen recording, code snippet

via the UI:

CleanShot.2022-12-22.at.13.37.50.mp4

via Javascript run in the editor:

wp.data.dispatch("core/edit-post").hideBlockTypes(["core/paragraph"]);

Environment info

WordPress version 6.1.1. The Gutenberg plugin is not active.

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

---

This issue is discussed in #23603 in the context of inner blocks, but this problem much wider in scope.

[t-hamano]

@cbirdsong

Thank you for submitting the issue.

I believe this is the intended behavior. By #15021, the insert button is intentionally hidden if the default block (i.e. paragraph block) cannot be inserted.

edit: I missed #23603 which you noted at the end. It may need improvement as described in this issue.

[cbirdsong]

This is very unintuitive behavior, especially considering it occurs when the paragraph block has only been hidden, not removed entirely.

[ntsekouras]

Hm.. I don't think we can make arbitrary decisions about setting a new default block, but maybe we would need a way to set the default block from the UI? 🤔

[cbirdsong]

It seems like the most sensible solution would be a new default block whose only job is to show the inserter and the "type / to choose a block" prompt, perhaps conditionally based on if it's a restricted inner blocks container like the buttons block.

By default it could allow typing anything prefixed with a /, and if the paragraph block is registered it could also allow content that isn't prefixed by /, which would transform it into a paragraph block once that happens?

[cooperfellows]

Love the idea of an "inserter block" that can be utilized in these instances, like how @gwwar outlines in the second approach outlined in #23603 (comment).

Our use case is that we have disabled the default paragraph block at the highest level, and only allow it as an innerBlock in some custom Gutenberg blocks that we have developed.

[rleecrewmp]

Hm.. I don't think we can make arbitrary decisions about setting a new default block, but maybe we would need a way to set the default block from the UI? 🤔

Is there a reason we can't have it just open the block picker if there is no default block available?