Navigation link: prime caches for all posts in menu items

[spacedmonkey]

What?

For menu items in the navigation, instead of loading each post one at a time, load all posts into memory by get all post ids and running them through the _prime_post_caches function.
Fixes #40750.

Why?

This improves database performance.

How?

Testing Instructions

Screenshots or screencast

[felixarntz]

@spacedmonkey Mostly looks good, just a few minor comments.

The higher-level feedback though is that I think we should add a test for this.

[adamsilverstein]

Looks good to me

[costdev]

Some minor docblock suggestions and some stricter assertions.

[spacedmonkey]

@anton-vlasenko @draganescu @gziolo Any recommendation on this PR to improve the backport. The files in 6.1 compat file do not seem right to be but it was the only way to get the unit tests to run.

[peterwilsoncc]

This looks sensible to me, I've added a note about a more complex test but it would be great to have the cache priming in even if the test waits a little longer.

[adamziel]

@spacedmonkey when I checked in the build files (build/block-library/blocks/navigation.php) how do these functions come through when defined with the block, this is what I saw:

/**
 * Get post IDs from a navigation link block instance.
 *
 * @param WP_Block $block Instance of a block.
 *
 * @return array Array of post IDs.
 */
function gutenberg_gutenberg_block_core_navigation_get_post_ids_from_block( $block ) {
	$post_ids = array();

	if ( $block->inner_blocks ) {
		$post_ids = gutenberg_block_core_navigation_get_post_ids( $block->inner_blocks );
	}

	if ( 'core/navigation-link' === $block->name || 'core/navigation-submenu' === $block->name ) {
		if ( $block->attributes && isset( $block->attributes['kind'] ) && 'post-type' === $block->attributes['kind'] ) {
			$post_ids[] = $block->attributes['id'];
		}
	}

	return $post_ids;
}

/**
 * Iterate through all inner blocks recursively and get navigation link block's post IDs.
 *
 * @param WP_Block_List $inner_blocks Block list class instance.
 *
 * @return array Array of post IDs.
 */
function gutenberg_block_core_navigation_get_post_ids( $inner_blocks ) {
	$post_ids = array_map( 'gutenberg_block_core_navigation_get_post_ids_from_block', iterator_to_array( $inner_blocks ) );
	return array_unique( array_merge( ...$post_ids ) );
}

I have no idea where does the double gutenberg_gutenberg_ prefix come from yet, but that's likely the culprit here.

[spacedmonkey]

@adamziel So what do you recommend here? Is this PR okay as it is?

[adamziel]

@spacedmonkey I'd like to see these functions bundled with the navigation block since they are only needed there. At the same time, the time before the RC2 is short and this looks like a bug in the build process. I am investigating whether this can be fixed quickly.

[adamziel]

@spacedmonkey got it! The matcher finds function block_core_navigation_get_post_ids in that file and replaces block_core_navigation_get_post_ids with gutenberg_block_core_navigation_get_post_ids In the process, block_core_navigation_get_post_ids_from_block gets renamed to gutenberg_block_core_navigation_get_post_ids_from_block. Then, the matcher acts on the block_core_navigation_get_post_ids_from_block, hence the double prefix.

If you rename these functions in such a way that the name of the first is not a substring of a second, it should work. You may also need to call the gutenberg_ prefixed version in the tests.

I've filed an issue to keep track of this problem separately: #40938

[spacedmonkey]

@adamziel Thanks. I have pushed up a change.

[adamziel]

I cherry-picked this to wp/6.0 branch to be included in WordPress 6.0 RC2 later today 57e4435

[gziolo]

We will still need to add unit tests separately to WordPress core.