Add plugin template registration API

lib/block-templates.php

@@ -0,0 +1,14 @@
+<?php
+/**
+ * Block template functions.
+ *
+ * @package gutenberg
+ */
+
+function gutenberg_register_block_template( $template_name, $args = array() ) {
+	return WP_Block_Templates_Registry::get_instance()->register( $template_name, 'wp_template', $args );
+}
+
+function gutenberg_register_block_template_part( $template_name, $args = array() ) {
+	return WP_Block_Templates_Registry::get_instance()->register( $template_name, 'wp_template_part', $args );
+}

lib/class-wp-block-templates-registry.php

@@ -0,0 +1,249 @@
+<?php
+/**
+ * Block template functions.
+ *
+ * @package gutenberg
+ */
+
+final class WP_Block_Templates_Registry {
+	private $registered_block_templates = array(
+		'wp_template' => array(),
+		'wp_template_part' => array()
+	);
+	private static $instance = null;
+
+	public function register( $template_name, $template_type, $args = array() ) {
+
+		$template = null;
+		if ( $template_name instanceof WP_Block_Template ) {
+			$template = $template_name;
+			$template_name       = $template->name;
+		}
+
+		if ( ! is_string( $template_name ) ) {
+			_doing_it_wrong(
+				__METHOD__,
+				__( 'Block template names must be strings.' ),
+				'6.6.0'
+			);
+			return false;
+		}
+
+		if ( 'wp_template' !== $template_type && 'wp_template_part' !== $template_type ) {
+			_doing_it_wrong(
+				__METHOD__,
+				__( 'Block templates need to be of `wp_template` or `wp_template_part` type.' ),
+				'6.6.0'
+			);
+			return false;
+		}
+
+		if ( preg_match( '/[A-Z]+/', $template_name ) ) {
+			_doing_it_wrong(
+				__METHOD__,
+				__( 'Block template names must not contain uppercase characters.' ),
+				'6.6.0'
+			);
+			return false;
+		}
+
+		$name_matcher = '/^[a-z0-9-]+\/\/[a-z0-9-]+$/';
+		if ( ! preg_match( $name_matcher, $template_name ) ) {
+			_doing_it_wrong(
+				__METHOD__,
+				__( 'Block template names must contain a namespace prefix. Example: my-plugin/my-custom-template' ),
+				'6.6.0'
+			);
+			return false;
+		}
+
+		if ( $this->is_registered( $template_type, $template_name ) ) {
+			_doing_it_wrong(
+				__METHOD__,
+				/* translators: %s: Template name. */
+				sprintf( __( 'Template "%s" is already registered.' ), $template_name ),
+				'6.6.0'
+			);
+			return false;
+		}
+
+		if ( ! $template ) {
+			$theme_name = get_stylesheet();
+			$template = new WP_Block_Template();
+			$template->id             = $theme_name . '//' . $args['slug'];
+			$template->theme          = $theme_name; // @todo If not attached to the theme, this should be the plugin URI.
+			$template->plugin         = array_key_exists( 'plugin', $args ) ? $args[ 'plugin' ] : '';
+			$template->author         = null;
+			$template->content        = array_key_exists( 'path', $args ) ? file_get_contents( $args[ 'path' ] ) : '';
+			$template->source         = 'plugin';
+			$template->slug           = array_key_exists( 'slug', $args ) ? $args['slug'] : '';
+			$template->type           = $template_type;
+			$template->title          = array_key_exists( 'title', $args ) ? $args['title'] : '';
+			$template->description    = array_key_exists( 'description', $args ) ? $args['description'] : '';
+			$template->status         = 'publish';
+			$template->has_theme_file = true;
+			$template->origin         = 'plugin';
+			$template->is_custom      = false;
+			$template->post_types     = array_key_exists( 'post_types', $args ) ? $args['post_types'] : '';
+			$template->area           = $template_type === 'wp_template_part' && array_key_exists( 'area', $args ) ? $args['area'] : '';
+		}
+
+		$this->registered_block_templates[ $template_type ][ $template_name ] = $template;
+
+		return $template;
+	}
+
+	public function get_by_slug( $template_type, $template_slug ) {
+		$all_templates = $this->get_all_registered( $template_type );
+
+		if ( ! $all_templates ) {
+			return null;
+		}
+
+		foreach( $all_templates as $template_name => $template ) {
+			if ( $template->slug === $template_slug ) {
+				return $template;
+			}
+		}
+
+		return null;
+	}
+
+	/**
+	 * Retrieves a registered template.
+	 *
+	 * @since 6.6.0
+	 *
+	 * @param string $template_type Template type, either `wp_template` or `wp_template_part`.
+	 * @param string $template_name Block type name including namespace.
+	 * @return WP_Block_Type|null The registered block type, or null if it is not registered.
+	 */
+	public function get_registered( $template_type, $template_name ) {
+		if ( 'wp_template' !== $template_type && 'wp_template_part' !== $template_type ) {
+			_doing_it_wrong(
+				__METHOD__,
+				__( 'Only valid block template types are `wp_template` and `wp_template_part`.' ),
+				'6.6.0'
+			);
+			return false;
+		}
+
+		if ( ! $this->is_registered( $template_type, $template_name ) ) {
+			return null;
+		}
+
+		return $this->registered_block_templates[ $template_type ][ $template_name ];
+	}
+
+	/**
+	 * Retrieves all registered block templates by type.
+	 *
+	 * @since 6.6.0
+	 *
+	 * @param string $template_type Template type, either `wp_template` or `wp_template_part`.
+	 * @return WP_Block_Template[] Associative array of `$block_type_name => $block_type` pairs.
+	 */
+	public function get_all_registered( $template_type ) {
+		if ( 'wp_template' !== $template_type && 'wp_template_part' !== $template_type ) {
+			_doing_it_wrong(
+				__METHOD__,
+				__( 'Only valid block template types are `wp_template` and `wp_template_part`.' ),
+				'6.6.0'
+			);
+			return false;
+		}
+
+		return $this->registered_block_templates[ $template_type ];
+	}
+
+	/**
+	 * Retrieves all registered block templates by type.
+	 *
+	 * @since 6.6.0
+	 *
+	 * @param string $template_type Template type. Either 'wp_template' or 'wp_template_part'.
+	 * @param array  $query {
+	 *     Arguments to retrieve templates. Optional, empty by default.
+	 *
+	 *     @type string[] $slug__in     List of slugs to include.
+	 *     @type string[] $slug__not_in List of slugs to skip.
+	 *     @type string   $area         A 'wp_template_part_area' taxonomy value to filter by (for 'wp_template_part' template type only).
+	 *     @type string   $post_type    Post type to get the templates for.
+	 * }
+	 */
+	public function get_by_query( $template_type, $query = array() ) {
+		$all_templates = $this->get_all_registered( $template_type );
+
+		if ( ! $all_templates ) {
+			return array();
+		}
+
+		$slugs_to_include = isset( $query['slug__in'] ) ? $query['slug__in'] : array();
+		$slugs_to_skip    = isset( $query['slug__not_in'] ) ? $query['slug__not_in'] : array();
+		$area             = isset( $query['area'] ) ? $query['area'] : null;
+		$post_type        = isset( $query['post_type'] ) ? $query['post_type'] : '';
+
+		foreach( $all_templates as $template_name => $template ) {
+			if ( ! empty( $slugs_to_include ) && ! in_array( $template->slug, $slugs_to_include ) ) {
+				unset( $all_templates[ $template_name ] );
+			}
+
+			if ( ! empty( $slugs_to_skip ) && in_array( $template->slug, $slugs_to_skip ) ) {
+				unset( $all_templates[ $template_name ] );
+			}
+
+			if ( 'wp_template_part' === $template_type && $template->area !== $area ) {
+				unset( $all_templates[ $template_name ] );
+			}
+
+			if ( ! empty( $post_type ) && ! in_array( $post_type, $template->post_types ) ) {
+				unset( $all_templates[ $template_name ] );
+			}
+		}
+
+		return $all_templates;
+	}
+
+	/**
+	 * Checks if a block template is registered.
+	 *
+	 * @since 6.6.0
+	 *
+	 * @param string $template_type Template type, either `wp_template` or `wp_template_part`.
+	 * @param string $template_name Block type name including namespace.
+	 * @return bool True if the template is registered, false otherwise.
+	 */
+	public function is_registered( $template_type, $template_name ) {
+		if ( 'wp_template' !== $template_type && 'wp_template_part' !== $template_type ) {
+			_doing_it_wrong(
+				__METHOD__,
+				__( 'Only valid block template types are `wp_template` and `wp_template_part`.' ),
+				'6.6.0'
+			);
+			return false;
+		}
+
+		return isset( $this->registered_block_templates[ $template_type ][ $template_name ] );
+	}
+
+	public function unregister( $template_name ) {
+		// @todo
+	}
+
+	/**
+	 * Utility method to retrieve the main instance of the class.
+	 *
+	 * The instance will be created if it does not exist yet.
+	 *
+	 * @since 6.6.0
+	 *
+	 * @return WP_Block_Templates_Registry The main instance.
+	 */
+	public static function get_instance() {
+		if ( null === self::$instance ) {
+			self::$instance = new self();
+		}
+
+		return self::$instance;
+	}
+}

lib/compat/wordpress-6.5/rest-api.php

@@ -86,7 +86,7 @@ function _gutenberg_get_wp_templates_author_text_field( $template_object ) {
 			return empty( $theme_name ) ? $template_object['theme'] : $theme_name;
 		case 'plugin':
 			$plugins = get_plugins();
-			$plugin  = $plugins[ plugin_basename( sanitize_text_field( $template_object['theme'] . '.php' ) ) ];
+			$plugin = $plugins[ plugin_basename( sanitize_text_field( $template_object['theme'] . '.php' ) ) ];
 			return empty( $plugin['Name'] ) ? $template_object['theme'] : $plugin['Name'];
 		case 'site':
 			return get_bloginfo( 'name' );

lib/compat/wordpress-6.6/block-template-utils.php

@@ -340,6 +340,20 @@ function gutenberg_get_block_templates( $query = array(), $template_type = 'wp_t
 		foreach ( $template_files as $template_file ) {
 			$query_result[] = _build_block_template_result_from_file( $template_file, $template_type );
 		}
+
+		/*
+		 * Add templates registered in the template registry. Filtering out the ones which have a theme file.
+		 */
+		$registered_templates = WP_Block_Templates_Registry::get_instance()->get_by_query( $template_type, $query );
+		$matching_registered_templates = array_filter( $registered_templates, function( $registered_template ) use ( $template_files ) {
+			foreach ( $template_files as $template_file ) {
+				if ( $template_file['slug'] === $registered_template->slug ) {
+					return false;
+				}
+			}
+			return true;
+		} );
+		$query_result = array_merge( $query_result, $matching_registered_templates );
 	}
 
 	/**