Build: Restore block parser in Core.

.gitignore

@@ -38,9 +38,6 @@ wp-tests-config.php
 /src/wp-includes/blocks/*
 !/src/wp-includes/blocks/index.php
 /src/wp-includes/build
-/src/wp-includes/class-wp-block-parser.php
-/src/wp-includes/class-wp-block-parser-block.php
-/src/wp-includes/class-wp-block-parser-frame.php
 /src/wp-includes/theme.json
 /packagehash.txt
 /.gutenberg-hash

src/wp-includes/blocks.php

@@ -2421,10 +2421,6 @@ function parse_blocks( $content ) {
 	 */
 	$parser_class = apply_filters( 'block_parser_class', 'WP_Block_Parser' );
 
-	if ( ! class_exists( $parser_class ) ) {
-		return array();
-	}
-
 	$parser = new $parser_class();
 	return $parser->parse( $content );
 }

src/wp-includes/class-wp-block-parser-block.php

@@ -0,0 +1,90 @@
+<?php
+/**
+ * Block Serialization Parser
+ *
+ * @package WordPress
+ */
+
+/**
+ * Class WP_Block_Parser_Block
+ *
+ * Holds the block structure in memory
+ *
+ * @since 5.0.0
+ */
+class WP_Block_Parser_Block {
+	/**
+	 * Name of block
+	 *
+	 * @example "core/paragraph"
+	 *
+	 * @since 5.0.0
+	 * @var string
+	 */
+	public $blockName; // phpcs:ignore WordPress.NamingConventions.ValidVariableName
+
+	/**
+	 * Optional set of attributes from block comment delimiters
+	 *
+	 * @example null
+	 * @example array( 'columns' => 3 )
+	 *
+	 * @since 5.0.0
+	 * @var array|null
+	 */
+	public $attrs;
+
+	/**
+	 * List of inner blocks (of this same class)
+	 *
+	 * @since 5.0.0
+	 * @var WP_Block_Parser_Block[]
+	 */
+	public $innerBlocks; // phpcs:ignore WordPress.NamingConventions.ValidVariableName
+
+	/**
+	 * Resultant HTML from inside block comment delimiters
+	 * after removing inner blocks
+	 *
+	 * @example "...Just <!-- wp:test /--> testing..." -> "Just testing..."
+	 *
+	 * @since 5.0.0
+	 * @var string
+	 */
+	public $innerHTML; // phpcs:ignore WordPress.NamingConventions.ValidVariableName
+
+	/**
+	 * List of string fragments and null markers where inner blocks were found
+	 *
+	 * @example array(
+	 *   'innerHTML'    => 'BeforeInnerAfter',
+	 *   'innerBlocks'  => array( block, block ),
+	 *   'innerContent' => array( 'Before', null, 'Inner', null, 'After' ),
+	 * )
+	 *
+	 * @since 5.0.0
+	 * @var array
+	 */
+	public $innerContent; // phpcs:ignore WordPress.NamingConventions.ValidVariableName
+
+	/**
+	 * Constructor.
+	 *
+	 * Will populate object properties from the provided arguments.
+	 *
+	 * @since 5.0.0
+	 *
+	 * @param string $name          Name of block.
+	 * @param array  $attrs         Optional set of attributes from block comment delimiters.
+	 * @param array  $inner_blocks  List of inner blocks (of this same class).
+	 * @param string $inner_html    Resultant HTML from inside block comment delimiters after removing inner blocks.
+	 * @param array  $inner_content List of string fragments and null markers where inner blocks were found.
+	 */
+	public function __construct( $name, $attrs, $inner_blocks, $inner_html, $inner_content ) {
+		$this->blockName    = $name;          // phpcs:ignore WordPress.NamingConventions.ValidVariableName
+		$this->attrs        = $attrs;
+		$this->innerBlocks  = $inner_blocks;  // phpcs:ignore WordPress.NamingConventions.ValidVariableName
+		$this->innerHTML    = $inner_html;    // phpcs:ignore WordPress.NamingConventions.ValidVariableName
+		$this->innerContent = $inner_content; // phpcs:ignore WordPress.NamingConventions.ValidVariableName
+	}
+}

src/wp-includes/class-wp-block-parser-frame.php

@@ -0,0 +1,79 @@
+<?php
+/**
+ * Block Serialization Parser
+ *
+ * @package WordPress
+ */
+
+/**
+ * Class WP_Block_Parser_Frame
+ *
+ * Holds partial blocks in memory while parsing
+ *
+ * @internal
+ * @since 5.0.0
+ */
+class WP_Block_Parser_Frame {
+	/**
+	 * Full or partial block
+	 *
+	 * @since 5.0.0
+	 * @var WP_Block_Parser_Block
+	 */
+	public $block;
+
+	/**
+	 * Byte offset into document for start of parse token
+	 *
+	 * @since 5.0.0
+	 * @var int
+	 */
+	public $token_start;
+
+	/**
+	 * Byte length of entire parse token string
+	 *
+	 * @since 5.0.0
+	 * @var int
+	 */
+	public $token_length;
+
+	/**
+	 * Byte offset into document for after parse token ends
+	 * (used during reconstruction of stack into parse production)
+	 *
+	 * @since 5.0.0
+	 * @var int
+	 */
+	public $prev_offset;
+
+	/**
+	 * Byte offset into document where leading HTML before token starts
+	 *
+	 * @since 5.0.0
+	 * @var int
+	 */
+	public $leading_html_start;
+
+	/**
+	 * Constructor
+	 *
+	 * Will populate object properties from the provided arguments.
+	 *
+	 * @since 5.0.0
+	 *
+	 * @param WP_Block_Parser_Block $block              Full or partial block.
+	 * @param int                   $token_start        Byte offset into document for start of parse token.
+	 * @param int                   $token_length       Byte length of entire parse token string.
+	 * @param int|null              $prev_offset        Optional. Byte offset into document for after parse token ends. Default null.
+	 * @param int|null              $leading_html_start Optional. Byte offset into document where leading HTML before token starts.
+	 *                                                  Default null.
+	 */
+	public function __construct( $block, $token_start, $token_length, $prev_offset = null, $leading_html_start = null ) {
+		$this->block              = $block;
+		$this->token_start        = $token_start;
+		$this->token_length       = $token_length;
+		$this->prev_offset        = isset( $prev_offset ) ? $prev_offset : $token_start + $token_length;
+		$this->leading_html_start = $leading_html_start;
+	}
+}