Block Hooks API: Insert metadata at the same time as hooked blocks

[tjcafferkey]

Trac ticket: https://core.trac.wordpress.org/ticket/59574

The block hooks UI toggle relies on the ignoredHookedBlocks when determining whether to show the toggle in the Site Editor UI. The current problem is that for uncustomized templates we don't add this meta data. Currently the visitor functions have a default callback of insert_hooked_blocks and we only add the meta data when we're writing to the database via an available filter in the template controller.

This PR creates a new default callback which both inserts the hooked blocks and adds the ignoredHookedBlocks meta data to the anchor block, and makes this the new default callback for the visitor functions. This means we will continue to add ignoredHookedBlocks meta when writing to the database meaning this operation happens twice. Although not ideal this is necessary to cover the following scenarios;

• When the user adds an anchor block within the editor we still need to add the ignoredHookedBlocks meta to it to prevent hooked blocks hooking on to it unexpectedly on the frontend, this means we keep parity between the frontend and editor.
• When a user writes template data to the database directly through the API (instead of the editor) we need to again ensure we're not inserting hooked blocks unexpectedly.

It is worth noting that with this change it means the first hooked block to insert relative to its anchor block will be accepted. Any additional blocks of the same type (ie a second core/loginout block) trying to hook onto the same anchor block will be ignored, irrespective of the position.

Manual testing instructions:

1 . Clear template customizations
2. Add the first code block to your themes functions.php
3. Go to the Single Posts template and check the loginout block is inserted after the post content.
4. Click the post content to check the toggle exists to show/hide the hooked block.
5. Save the template
6. Add the second code block and reload the Single Posts template. Follow steps 1-4 again and check them against the Page List block.

function register_loginout_hooked_block( $hooked_blocks, $position, $anchor_block, $context ) {
	if ( $anchor_block === 'core/post-content' && $position === 'after' ) {
		$hooked_blocks[] = 'core/loginout';
	}

	return $hooked_blocks;
}
add_filter( 'hooked_block_types', 'register_loginout_hooked_block', 10, 4 );

function register_pagelist_hooked_block( $hooked_blocks, $position, $anchor_block, $context ) {
	if ( $anchor_block === 'core/post-content' && $position === 'before' ) {
		$hooked_blocks[] = 'core/page-list';
	}

	return $hooked_blocks;
}
add_filter( 'hooked_block_types', 'register_pagelist_hooked_block', 10, 4 );

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[github-actions]

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[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

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Props tomjcafferkey, bernhard-reiter, gziolo.

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[ockham]

Looking good overall, thank you! Just a few small thing we should tweak a bit 😄

[tjcafferkey]

@gziolo since @ockham is AFK I was wondering how I should proceed with this?

[ockham]

Works like a charm! Thank you very much for taking care of this 🚀

[ockham]

Committed to Core in https://core.trac.wordpress.org/changeset/58186.