register_block_type_from_metadata

register_block_type_from_metadata: 这个函数用来从一个包含块的选项和设置的元数据文件中注册一个新的块类型。它需要一个参数：$file。$file是包含块的选项的元数据文件的路径。

通过存储在`block.json`文件中的元数据注册一个块类型。

function register_block_type_from_metadata( $file_or_folder, $args = array() ) {
	/*
	 * Get an array of metadata from a PHP file.
	 * This improves performance for core blocks as it's only necessary to read a single PHP file
	 * instead of reading a JSON file per-block, and then decoding from JSON to PHP.
	 * Using a static variable ensures that the metadata is only read once per request.
	 */
	static $core_blocks_meta;
	if ( ! $core_blocks_meta ) {
		$core_blocks_meta = include_once ABSPATH . WPINC . '/blocks/blocks-json.php';
	}

	$metadata_file = ( ! str_ends_with( $file_or_folder, 'block.json' ) ) ?
		trailingslashit( $file_or_folder ) . 'block.json' :
		$file_or_folder;

	if ( ! file_exists( $metadata_file ) ) {
		return false;
	}

	// Try to get metadata from the static cache for core blocks.
	$metadata = false;
	if ( str_starts_with( $file_or_folder, ABSPATH . WPINC ) ) {
		$core_block_name = str_replace( ABSPATH . WPINC . '/blocks/', '', $file_or_folder );
		if ( ! empty( $core_blocks_meta[ $core_block_name ] ) ) {
			$metadata = $core_blocks_meta[ $core_block_name ];
		}
	}

	// If metadata is not found in the static cache, read it from the file.
	if ( ! $metadata ) {
		$metadata = wp_json_file_decode( $metadata_file, array( 'associative' => true ) );
	}

	if ( ! is_array( $metadata ) || empty( $metadata['name'] ) ) {
		return false;
	}
	$metadata['file'] = wp_normalize_path( realpath( $metadata_file ) );

	/**
	 * Filters the metadata provided for registering a block type.
	 *
	 * @since 5.7.0
	 *
	 * @param array $metadata Metadata for registering a block type.
	 */
	$metadata = apply_filters( 'block_type_metadata', $metadata );

	// Add `style` and `editor_style` for core blocks if missing.
	if ( ! empty( $metadata['name'] ) && 0 === strpos( $metadata['name'], 'core/' ) ) {
		$block_name = str_replace( 'core/', '', $metadata['name'] );

		if ( ! isset( $metadata['style'] ) ) {
			$metadata['style'] = "wp-block-$block_name";
		}
		if ( ! isset( $metadata['editorStyle'] ) ) {
			$metadata['editorStyle'] = "wp-block-{$block_name}-editor";
		}
	}

	$settings          = array();
	$property_mappings = array(
		'apiVersion'      => 'api_version',
		'title'           => 'title',
		'category'        => 'category',
		'parent'          => 'parent',
		'ancestor'        => 'ancestor',
		'icon'            => 'icon',
		'description'     => 'description',
		'keywords'        => 'keywords',
		'attributes'      => 'attributes',
		'providesContext' => 'provides_context',
		'usesContext'     => 'uses_context',
		'supports'        => 'supports',
		'styles'          => 'styles',
		'variations'      => 'variations',
		'example'         => 'example',
	);
	$textdomain        = ! empty( $metadata['textdomain'] ) ? $metadata['textdomain'] : null;
	$i18n_schema       = get_block_metadata_i18n_schema();

	foreach ( $property_mappings as $key => $mapped_key ) {
		if ( isset( $metadata[ $key ] ) ) {
			$settings[ $mapped_key ] = $metadata[ $key ];
			if ( $textdomain && isset( $i18n_schema->$key ) ) {
				$settings[ $mapped_key ] = translate_settings_using_i18n_schema( $i18n_schema->$key, $settings[ $key ], $textdomain );
			}
		}
	}

	$script_fields = array(
		'editorScript' => 'editor_script_handles',
		'script'       => 'script_handles',
		'viewScript'   => 'view_script_handles',
	);
	foreach ( $script_fields as $metadata_field_name => $settings_field_name ) {
		if ( ! empty( $metadata[ $metadata_field_name ] ) ) {
			$scripts           = $metadata[ $metadata_field_name ];
			$processed_scripts = array();
			if ( is_array( $scripts ) ) {
				for ( $index = 0; $index < count( $scripts ); $index++ ) {
					$result = register_block_script_handle(
						$metadata,
						$metadata_field_name,
						$index
					);
					if ( $result ) {
						$processed_scripts[] = $result;
					}
				}
			} else {
				$result = register_block_script_handle(
					$metadata,
					$metadata_field_name
				);
				if ( $result ) {
					$processed_scripts[] = $result;
				}
			}
			$settings[ $settings_field_name ] = $processed_scripts;
		}
	}

	$style_fields = array(
		'editorStyle' => 'editor_style_handles',
		'style'       => 'style_handles',
	);
	foreach ( $style_fields as $metadata_field_name => $settings_field_name ) {
		if ( ! empty( $metadata[ $metadata_field_name ] ) ) {
			$styles           = $metadata[ $metadata_field_name ];
			$processed_styles = array();
			if ( is_array( $styles ) ) {
				for ( $index = 0; $index < count( $styles ); $index++ ) {
					$result = register_block_style_handle(
						$metadata,
						$metadata_field_name,
						$index
					);
					if ( $result ) {
						$processed_styles[] = $result;
					}
				}
			} else {
				$result = register_block_style_handle(
					$metadata,
					$metadata_field_name
				);
				if ( $result ) {
					$processed_styles[] = $result;
				}
			}
			$settings[ $settings_field_name ] = $processed_styles;
		}
	}

	if ( ! empty( $metadata['render'] ) ) {
		$template_path = wp_normalize_path(
			realpath(
				dirname( $metadata['file'] ) . '/' .
				remove_block_asset_path_prefix( $metadata['render'] )
			)
		);
		if ( $template_path ) {
			/**
			 * Renders the block on the server.
			 *
			 * @since 6.1.0
			 *
			 * @param array    $attributes Block attributes.
			 * @param string   $content    Block default content.
			 * @param WP_Block $block      Block instance.
			 *
			 * @return string Returns the block content.
			 */
			$settings['render_callback'] = function( $attributes, $content, $block ) use ( $template_path ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
				ob_start();
				require $template_path;
				return ob_get_clean();
			};
		}
	}

	/**
	 * Filters the settings determined from the block type metadata.
	 *
	 * @since 5.7.0
	 *
	 * @param array $settings Array of determined settings for registering a block type.
	 * @param array $metadata Metadata provided for registering a block type.
	 */
	$settings = apply_filters(
		'block_type_metadata_settings',
		array_merge(
			$settings,
			$args
		),
		$metadata
	);

	return WP_Block_Type_Registry::get_instance()->register(
		$metadata['name'],
		$settings
	);
}