Block Hooks: Apply to Post Content (on frontend and in editor) #7898

ockham · 2024-11-26T16:38:17Z

Why does this work? And how?

It works the same way as in templates:

If a post is loaded on the frontend, Block Hooks will be applied to the post content, thus inserting hooked blocks.
If it is loaded in the editor, the Posts endpoint will inject both the hooked blocks, and the ignoredHookedBlocks metadata (into anchor blocks).
This means that if the post is modified in the editor -- including moving or deleting of hooked blocks -- it will have that ignoredHookedBlocks metadata on individual anchor blocks persisted when saving.
Thus, when loading the post again on the frontend, no hooked blocks will be inserted next to anchor blocks that list them in their ignoredHookedBlocks. OTOH, any hooked blocks that were present when saving the post have now simply become part of the markup.

Testing Instructions, Part One

Start by installing the following plugin, but do not activate it yet:

Plugin code

<?php
/**
 * Plugin Name:       Insert Separator blocks Before Headings.
 * Description:       Block Hooks demo plugin that inserts Separator blocks before Heading blocks.
 * Version:           0.1.0
 * Requires at least: 6.7
 */

defined( 'ABSPATH' ) || exit;

function insert_separators_before_headings( $hooked_blocks, $position, $anchor_block, $context ) {
	if ( ! $context instanceof WP_Post ) {
		return $hooked_blocks;
	}

	if ( $anchor_block === 'core/heading' && $position === 'before' ) {
		$hooked_blocks[] = 'core/separator';
	}

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

function set_separator_block_inner_html( $hooked_block, $hooked_block_type, $relative_position, $anchor_block ) {
	if ( $anchor_block['blockName'] === 'core/heading' && 'before' === $relative_position ) {
        $hooked_block['innerContent'] = array( '<hr class="wp-block-separator has-alpha-channel-opacity"/>' );
	}

	return $hooked_block;
}
add_filter( 'hooked_block_core/separator', 'set_separator_block_inner_html', 10, 4 );

Create a new post that contains a number of headings and paragraphs.
Save that post, and view it on the frontend. Keep it open in a tab.
Activate the plugin.
Go back to the tab with the post (on the frontend). Reload.
Verify that before each heading, a separator (i.e. a horizontal line) has been inserted.
Open the post in the editor, and verify that the separators are also present there.
Modify the separators -- e.g. move one of them around and delete another. Save the post again.
Reload it on the frontend again. Verify that the changes you made in the editor are respected.

Screenshots or screencast

Testing Instructions, Part Two

Edit: The behavior covered by the following testing instructions changed after I wrote them, as @sirreal noticed here. We ended up deciding that the new behavior -- where hooked blocks would not be inserted if the anchor block was added after the post was added might be preferable, see this comment on the companion GB PR.

Now edit the post, and insert another heading at the bottom. Note that no separator is inserted at the client side "right away" -- the reason is that Block Hooks are almost exclusively handled on the server side. This is one minor UX inconsistency -- the same inconsistency is present in templates.
~~Save the post, and reload it on the frontend. Note that a separator has now been inserted before the newly added heading!~~ ✨
~~Finally, reload the post in the editor. Note that the separator is now also present there.~~

Screenshots or screencast, Part Two

Trac ticket: https://core.trac.wordpress.org/ticket/61074

This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

github-actions · 2024-11-26T16:50:57Z

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src/wp-includes/default-filters.php

ockham · 2024-11-27T19:01:08Z

src/wp-includes/blocks.php

+	$content = apply_block_hooks_to_content(
+		$content,
+		$post,
+		'insert_hooked_blocks_and_set_ignored_hooked_blocks_metadata'
+	);


We're now inserting hooked blocks and setting ignoredHookedBlocks metadata. Previously, we were only inserting hooked blocks (i.e. the default behavior of apply_block_hooks_to_content when no third argument is given).

This change also affects the Navigation block. We need to make sure that any hooked blocks inside of the Navigation block -- both as first/last child of core/navigation itself, but also after/before blocks inside of the Navigation block -- still work (both on the frontend and in the editor.

To test if the Navigation block still works, we can follow the testing instructions from WordPress/gutenberg#59021.

Turns out there was an unrelated issue with this. I've filed a fix: #7941

I've committed #7941 to Core [62639], and rebased this PR to include the fix.

github-actions · 2024-11-27T19:53:33Z

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.

Core Committers: Use this line as a base for the props when committing in SVN:

Props bernhard-reiter, gziolo, jonsurrell, karolmanijak, leewillis77.

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

ockham · 2024-11-27T19:57:21Z

FYI @kmanijak. Maybe you can give this a try and let me know if it works for the purpose you're interested in! 😊

src/wp-includes/blocks.php

ockham · 2024-11-28T15:01:05Z

src/wp-includes/default-filters.php

@@ -192,6 +192,7 @@
 add_filter( 'the_title', 'convert_chars' );
 add_filter( 'the_title', 'trim' );

+add_filter( 'the_content', 'apply_block_hooks_to_content', 8 ); // BEFORE do_blocks().


Quoting #7889 (comment):

apply_block_hooks_to_content parses blocks, traverses the block tree (to insert hooked blocks), and reserializes them. Note that it's followed immediately by do_blocks (on the line below), which also parses blocks.

This means that in theory, there's some potential for optimization (parse only once inside of do_blocks, and traverse to insert hooked blocks there).

In practice, I'm not sure if that's viable, or if that might cause some collisions; in particular if do_blocks is already used in other contexts where hooked blocks are already inserted (through a different mechanism), e.g. in templates or wp_navigation posts.

kmanijak · 2024-11-28T19:32:47Z

FYI @kmanijak. Maybe you can give this a try and let me know if it works for the purpose you're interested in! 😊

Thank you @ockham for working on this! 🚀 I gave it a try and at first glance it works as expected! I can achieve the goals raised in scope of the discussion in WooCommerce. I'll play with it more tomorrow to check if I see any problems.

One potential feature I can already see (but obviously not the scope for this PR!) is the ability for more strict selectors. For example: $anchor_block as core/post-title but only within Query Loop, not any core/post-title, including the main post title. This very specific example can be workaround by checking if ($context instanceof WP_Post) { but wanted to give some generic example.

Anyway, looking good, thank you! 🙌

leewillis77 · 2024-11-29T10:55:22Z

Just following up on @kmanijak's comments. We flagged this as an issue to the Woo team, specifically about hooking blocks into Woo's Product Collection block when it was included in pages. Unfortunately, the patch here doesn't appear to resolve the issues we were seeing (we're unable to add hooked blocks inside the Product Collection block).

It's possible that the issue is Woo-specific (or on our side), but I just wanted to drop my observations here in case it is fundamental to the solution.
woocommerce/woocommerce#44776 (reply in thread)

leewillis77 · 2024-11-29T13:22:57Z

I'm testing with the WP 6.7.1 with the patch from this issue. Are there other dependent changes to make this work (ie would I have to start with WP trunk?)

ockham · 2024-12-02T12:56:10Z

Thanks a lot for testing, @leewillis77! I'm a bit puzzled as to why this wouldn't work if patched against 6.7.1; there shouldn't really be any dependent changes required for this.

Can you maybe try with the playground link (from this comment)?

ockham · 2024-12-02T12:58:43Z

For reviewers: @kmanijak has kindly tested this using the Woo Product Collection block and my Like Button block in a number of different scenarios 🙂

leewillis77 · 2024-12-02T14:18:52Z

@ockham @kmanijak I've re-tested this today (fresh install, re-patch etc.), and can confirm that block hooks are fired correctly on posts/pages. No idea why we couldn't get this working last week.

However, trying our actual implementation rather than just artificial tests I don't think this is going to give us what we actually need (what was originally raised on the WooCommerce discussion) due to the lack of contextual information (as @kmanijak alluded to in #7898 (comment)).

Ideally what we need in block hooks when we're deciding whether or not to hook a block in or not is the context of where it is. This is the same issue I originally raised in WordPress/gutenberg#54904 (comment). It's particularly bad here as the $context isn't even the top-level block, but a WP_Post object so we don't even have any idea what top-level block is being rendered so that we can make an informed decision about whether we should be hooking in or not.

src/wp-includes/blocks.php

gziolo · 2024-12-03T05:30:16Z

src/wp-includes/blocks.php

@@ -1286,22 +1293,44 @@ function insert_hooked_blocks_into_rest_response( $response, $post ) {
 			'ignoredHookedBlocks' => $ignored_hooked_blocks,
 		);
 	}
+
+	if ( 'wp_navigation' === $post->post_type ) {


What about synced patterns wp/block? Should it be extensible? These post types are special do maybe it’s fine as is but a filter here could be useful.

Ah, good point. I guess the wp_block post type should map to core/block.

A filter might make sense here 👍 Something to map post types to block types. (I wonder if we already have a function or data structure to do that somewhere 🤔 )

src/wp-includes/default-filters.php

ockham · 2024-12-03T10:37:47Z

src/wp-includes/default-filters.php

+add_filter( 'rest_prepare_page', 'insert_hooked_blocks_into_rest_response', 10, 2 );
+add_filter( 'rest_prepare_post', 'insert_hooked_blocks_into_rest_response', 10, 2 );


This follows the precedent of rest_prepare_wp_navigation below. However, it has the unfortunate side effect that Block Hooks aren't automatically applied to user-defined CPTs; those would need to be added manually (via add_filter( 'rest_prepare_my_cpt', ... )). (AFAIK, there's no "generic" rest_prepare filter that could cover all post types.)

I wonder if we should run insert_hooked_blocks_into_rest_response from inside the Posts controller instead, in order to insert hooked blocks into every CPT that has show_in_rest set to true 🤔 cc/ @gziolo

This reverts commit 41d13d0.

ockham · 2024-12-04T14:58:43Z

@gziolo Since insertion as the Post Content block's first or last child required changes to that block's PHP, I've updated the Gutenberg PR -- it also includes the required compat layer changes backported from this PR. Would you mind reviewing giving the GB PR a look?

There are a few open questions on this PR:

Add filter to allow different post type/block type mappings?
Use rest_prepare_ hook to insert hooked blocks into REST API response, or add inline in controller?

However, I don't think that those should be blockers for the Gutenberg PR. Both of them deserve some more consideration, but we might do that as part of this PR -- possibly even after the GB PR has landed 😊

sirreal · 2024-12-11T11:02:49Z

I was following the testing instructions from the description and when I add more headings the separator is not being added 😕

Testing Instructions, Part Two
…

Save the post, and reload it on the frontend. Note that a separator has now been inserted before the newly added heading! ✨

Finally, reload the post in the editor. Note that the separator is now also present there.

sirreal · 2024-12-11T11:05:38Z

I was following the testing instructions from the description and when I add more headings the separator is not being added 😕

When I add more headers they all look like this, which I believe is not intended according to the testing instructions:

<!-- wp:heading {"level":1,"metadata":{"ignoredHookedBlocks":["core/separator"]}} -->
<h1 class="wp-block-heading">text</h1>
<!-- /wp:heading -->

ockham · 2024-12-12T14:00:04Z

@sirreal Good spot! Turns out @gziolo noticed the same thing over at the GB PR. I replied there. The tl;dr is

Apologies, I think that this change in behavior is a side effect of some code I pushed after I wrote the testing instructions.
It's actually not bad in terms of UX -- a bit more predictable maybe. I'm happy to just consider it a happy accident and land it as-is.

So we might keep it this way. I'll add a note to the testing instructions.

sirreal

This tests well for me. I'm not well versed in block hooks but the changes seem reasonable. I've left a few notes, but I think this can be merged if you're confident.

sirreal · 2024-12-13T11:20:52Z

src/wp-includes/blocks.php

+	if ( null === $context ) {
+		$context = get_post();
+	}


Could this still be null and would that be a problem? null is in the return type of get_post().

Hmm, good question 🤔 The Block Hooks algorithm should work even with no $context specified -- it started out as an optional argument that filters such as hooked_block_types could use to conditionally insert hooked blocks based on context.

I think that that should still be the case, but I might wanna double-check 👍

Seems fine. I've added test coverage in a7693b0.

src/wp-includes/blocks.php

Co-authored-by: Jon Surrell <[email protected]>

ockham self-assigned this Nov 26, 2024

ockham commented Nov 26, 2024

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This was referenced Nov 26, 2024

Block Hooks: Apply to Post Content (on frontend) #7889

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Block Hooks: Apply to Post Content (on frontend and in editor) WordPress/gutenberg#67272

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ockham commented Nov 27, 2024

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ockham marked this pull request as ready for review November 27, 2024 19:53

ockham requested review from mtias and gziolo November 27, 2024 19:53

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Block Hooks: Fix context in update_ignored_hooked_blocks_postmeta #7941

Closed

ockham added 7 commits December 4, 2024 13:08

Block Hooks: Apply to Post Content (on frontend)

0711c61

Solve by using a default instead

b40dd94

Insert hooked block into editor

20a5470

Update PHPDoc

90abff4

Set ignoredHookedBlocks in REST API response

0b844b3

Also apply to pages

838a75e

Update PHPDoc

6793b55

ockham and others added 11 commits December 4, 2024 13:08

Tweak PHPDoc

2958c64

More PHPDoc tweaking

74b39fa

Temporarily remove filter

007d7a4

Bail early if no content is given

1d98a27

Revert "Bail early if no content is given"

c6c8481

This reverts commit 41d13d0.

Tighten checks

f29b288

Add since PHPDoc

a5cb598

Update ignoredHookedBlocks post meta on save

886d375

Add back check for post_type

89b835d

Tweak @SInCE PHPDoc

e14db01

Tweak param description

7635d23

ockham force-pushed the update/apply-block-hooks-to-post-content-and-editor branch from ff37889 to 7635d23 Compare December 4, 2024 12:08

sirreal approved these changes Dec 13, 2024

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ockham mentioned this pull request Dec 16, 2024

Block Hooks: Try Streaming Parser #8006

Draft

ockham and others added 2 commits December 16, 2024 15:41

Add comments to clarify removal/re-adding of the_content filter

2b7d36a

Co-authored-by: Jon Surrell <[email protected]>

Add test case for context set to null

a7693b0

Provide feedback

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Block Hooks: Apply to Post Content (on frontend and in editor) #7898

Block Hooks: Apply to Post Content (on frontend and in editor) #7898

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		add_filter( 'rest_prepare_page', 'insert_hooked_blocks_into_rest_response', 10, 2 );
		add_filter( 'rest_prepare_post', 'insert_hooked_blocks_into_rest_response', 10, 2 );

Block Hooks: Apply to Post Content (on frontend and in editor) #7898

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Block Hooks: Apply to Post Content (on frontend and in editor) #7898

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ockham commented Nov 26, 2024 • edited Loading

Why does this work? And how?

Testing Instructions, Part One

Screenshots or screencast

Testing Instructions, Part Two

Screenshots or screencast, Part Two

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Test using WordPress Playground

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