Backport: Templates perf: resolve patterns server side

[ellatrix]

Note that this replaces #6559, which I hadn't created from my fork.

Trac ticket: https://core.trac.wordpress.org/ticket/61228

This is a single backport for the following PRs:

• Templates perf: resolve patterns server side gutenberg#60349
• Templates: only resolve patterns for REST API endpoints gutenberg#61757

To test: check the patterns endpoint and search for wp:pattern. There should be 0 results.

---

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[anton-vlasenko]

Adding PHPUnit tests would be beneficial since just looking at the source code makes it hard to tell if this function works as intended.

By the way, I noticed that the $inner_content function argument might not be necessary because it seems to only pass information that's already in the $blocks function argument.

What do you think?

[anton-vlasenko]

From what I know, there’s no need to add an empty line between the @param and @return tags. Also, I noticed the description for the @inner_content function argument is missing. Could that be added?

Suggested change

	* @param array $blocks An array blocks.
	*
	* @return array An array of blocks with patterns replaced by their content.
	* @param array $blocks An array blocks.
	* @param array $inner_content An optional array of inner content.
	* @return array An array of blocks with patterns replaced by their content.

[ellatrix]

This is meant to be a private arg, not sure if there's a better way https://github.com/WordPress/wordpress-develop/pull/6673/files#r1623854851

[anton-vlasenko]

As far as I know, there is no concept of a private argument in PHP. I'm also unsure how common it is to omit a function argument from a DocBlock if it is not intended for use.

However, there might be a solution to eliminate the need for the $inner_content function argument:

/**
 * Replaces patterns in a block tree with their content.
 *
 * @since 6.6.0
 *
 * @param array $blocks An array of blocks or a parent block.
 * @return array An array of blocks with patterns replaced by their content.
 */
function resolve_pattern_blocks( $blocks ) {
	// Keep track of seen references to avoid infinite loops.
	static $seen_refs = array();
	$i                = 0;
	$is_parent_block = ! empty( $blocks['innerBlocks'] );

	if ( $is_parent_block ) {
		// If it is a single block, $blocks must be reinitialized before it can be used.
		$block         = $blocks;
		$blocks        = $block['innerBlocks'];
		$inner_content = $block['innerContent'];
	}
	while ( $i < count( $blocks ) ) {
		if ( 'core/pattern' !== $blocks[ $i ]['blockName'] ) {
			if ( $is_parent_block ) {
				$blocks[ $i ] = resolve_pattern_blocks( $blocks[ $i ] );
			}
			++$i;
			continue;
		}
		$attrs = $blocks[ $i ]['attrs'];

		if ( empty( $attrs['slug'] ) ) {
			++$i;
			continue;
		}

		$slug = $attrs['slug'];

		if ( isset( $seen_refs[ $slug ] ) ) {
			// Skip recursive patterns.
			array_splice( $blocks, $i, 1 );
			continue;
		}

		$registry = WP_Block_Patterns_Registry::get_instance();
		$pattern  = $registry->get_registered( $slug );

		// Skip unknown patterns.
		if ( ! $pattern ) {
			++$i;
			continue;
		}

		$blocks_to_insert   = parse_blocks( $pattern['content'] );
		$seen_refs[ $slug ] = true;
		$blocks_to_insert   = resolve_pattern_blocks( $blocks_to_insert );
		unset( $seen_refs[ $slug ] );
		array_splice( $blocks, $i, 1, $blocks_to_insert );

		// If we have inner content, we need to insert nulls in the
		// inner content array, otherwise serialize_blocks will skip
		// blocks.
		if ( !empty( $inner_content ) ) {
			$null_indices  = array_keys( $inner_content, null, true );
			$content_index = $null_indices[ $i ];
			$nulls         = array_fill( 0, count( $blocks_to_insert ), null );
			array_splice( $inner_content, $content_index, 1, $nulls );
		}

		// Skip inserted blocks.
		$i += count( $blocks_to_insert );
	}

	if ( $is_parent_block ) {
		$block['innerBlocks']  = $blocks;
		$block['innerContent'] = $inner_content;
		return $block;
	}

	return $blocks;
}

Probably not optimal, but it passes the tests.

[ellatrix]

Tbh, I find it a bit more confusing. Also, why is it now sometimes returning a blocks array and sometimes one block?

[anton-vlasenko]

Tbh, I find it a bit more confusing.

I feel the same way.

why is it now sometimes returning a blocks array and sometimes one block?

I made this change to eliminate the $inner_content parameter, aiming to streamline the function's interface.
I've tried to refactor this function into two separate functions, but it didn't go well either. This likely indicates that the current structure might be the most efficient approach.

[anton-vlasenko]

If @inner_content is expected to be an array, it might be a good idea to explicitly check to ensure it is an array to avoid PHP warnings. Is there a guarantee that $blocks[$i]['innerBlocks'] is always an array?

Suggested change

	if ( $inner_content ) {
	if ( is_array( $inner_content ) && $inner_content ) {

[ellatrix]

This is always an array, yes, there's also an empty check below. Also this argument is meant to be private, not sure if there's a better way to do it.

[ellatrix]

@anton-vlasenko Yes, it needs unit tests, but I'm unfamiliar with unit test in PHP and core. Would you be able to assist?

[anton-vlasenko]

@anton-vlasenko Yes, it needs unit tests, but I'm unfamiliar with unit test in PHP and core. Would you be able to assist?

Yes, I can look into it.

[ellatrix]

By the way, I noticed that the $inner_content function argument might not be necessary because it seems to only pass information that's already in the $blocks function argument.

I inline commented on that, it is necessary to change because serialise will break if it's not adjusted

[ellatrix]

@anton-vlasenko Added unit tests

[anton-vlasenko]

I've been testing this PR for some time and it worked as intended. The only change I would make is to remove the else operator, as it's not needed and allows to remove nesting. However, this is not a blocker:

function resolve_pattern_blocks( $blocks, &$inner_content = null ) {
	// Keep track of seen references to avoid infinite loops.
	static $seen_refs = array();
	$i                = 0;
	while ( $i < count( $blocks ) ) {
		if ( 'core/pattern' !== $blocks[ $i ]['blockName'] ) {
			if ( ! empty( $blocks[ $i ]['innerBlocks'] ) ) {
				$blocks[ $i ]['innerBlocks'] = resolve_pattern_blocks(
					$blocks[ $i ]['innerBlocks'],
					$blocks[ $i ]['innerContent']
				);
			}
			++ $i;
			continue;
		}

		$attrs = $blocks[ $i ]['attrs'];

		if ( empty( $attrs['slug'] ) ) {
			++$i;
			continue;
		}

		$slug = $attrs['slug'];

		if ( isset( $seen_refs[ $slug ] ) ) {
			// Skip recursive patterns.
			array_splice( $blocks, $i, 1 );
			continue;
		}

		$registry = WP_Block_Patterns_Registry::get_instance();
		$pattern  = $registry->get_registered( $slug );

		// Skip unknown patterns.
		if ( ! $pattern ) {
			++$i;
			continue;
		}

		$blocks_to_insert   = parse_blocks( $pattern['content'] );
		$seen_refs[ $slug ] = true;
		$blocks_to_insert   = resolve_pattern_blocks( $blocks_to_insert );
		unset( $seen_refs[ $slug ] );
		array_splice( $blocks, $i, 1, $blocks_to_insert );

		// If we have inner content, we need to insert nulls in the
		// inner content array, otherwise serialize_blocks will skip
		// blocks.
		if ( $inner_content ) {
			$null_indices  = array_keys( $inner_content, null, true );
			$content_index = $null_indices[ $i ];
			$nulls         = array_fill( 0, count( $blocks_to_insert ), null );
			array_splice( $inner_content, $content_index, 1, $nulls );
		}

		// Skip inserted blocks.
		$i += count( $blocks_to_insert );
	}
	return $blocks;
}