Block Editor: Introduce block templates for classic themes.

With this patch, users will be able to create custom block based templates
and assign them to specific pages/posts.

Themes can also opt-out of this feature

Props bernhard-reiter, carlomanf.
Fixes #53176.

Built from https://develop.svn.wordpress.org/trunk@51003


git-svn-id: http://core.svn.wordpress.org/trunk@50612 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/edit-form-blocks.php

@@ -220,6 +220,7 @@ $editor_settings = array(
 	'supportsLayout'                       => WP_Theme_JSON_Resolver::theme_has_support(),
 	'__experimentalBlockPatterns'          => WP_Block_Patterns_Registry::get_instance()->get_all_registered(),
 	'__experimentalBlockPatternCategories' => WP_Block_Pattern_Categories_Registry::get_instance()->get_all_registered(),
+	'supportsTemplateMode'                 => current_theme_supports( 'block-templates' ),
 
 	// Whether or not to load the 'postcustom' meta box is stored as a user meta
 	// field so that we're not always loading its assets.

wp-includes/block-template-utils.php

@@ -0,0 +1,144 @@
+<?php
+/**
+ * Utilities used to fetch and create templates.
+ *
+ * @package WordPress
+ * @since 5.8.0
+ */
+
+/**
+ * Build a unified template object based a post Object.
+ *
+ * @access private
+ * @since 5.8.0
+ *
+ * @param WP_Post $post Template post.
+ *
+ * @return WP_Block_Template|WP_Error Template.
+ */
+function _build_template_result_from_post( $post ) {
+	$terms = get_the_terms( $post, 'wp_theme' );
+
+	if ( is_wp_error( $terms ) ) {
+		return $terms;
+	}
+
+	if ( ! $terms ) {
+		return new WP_Error( 'template_missing_theme', __( 'No theme is defined for this template.' ) );
+	}
+
+	$theme = $terms[0]->name;
+
+	$template                 = new WP_Block_Template();
+	$template->wp_id          = $post->ID;
+	$template->id             = $theme . '//' . $post->post_name;
+	$template->theme          = $theme;
+	$template->content        = $post->post_content;
+	$template->slug           = $post->post_name;
+	$template->source         = 'custom';
+	$template->type           = $post->post_type;
+	$template->description    = $post->post_excerpt;
+	$template->title          = $post->post_title;
+	$template->status         = $post->post_status;
+	$template->has_theme_file = false;
+
+	return $template;
+}
+
+/**
+ * Retrieves a list of unified template objects based on a query.
+ *
+ * @since 5.8.0
+ *
+ * @param array $query {
+ *     Optional. Arguments to retrieve templates.
+ *
+ *     @type array  $slug__in List of slugs to include.
+ *     @type int    $wp_id Post ID of customized template.
+ * }
+ * @param string $template_type wp_template.
+ *
+ * @return array Templates.
+ */
+function get_block_templates( $query = array(), $template_type = 'wp_template' ) {
+	$wp_query_args = array(
+		'post_status'    => array( 'auto-draft', 'draft', 'publish' ),
+		'post_type'      => $template_type,
+		'posts_per_page' => -1,
+		'no_found_rows'  => true,
+		'tax_query'      => array(
+			array(
+				'taxonomy' => 'wp_theme',
+				'field'    => 'name',
+				'terms'    => wp_get_theme()->get_stylesheet(),
+			),
+		),
+	);
+
+	if ( isset( $query['slug__in'] ) ) {
+		$wp_query_args['post_name__in'] = $query['slug__in'];
+	}
+
+	// This is only needed for the regular templates CPT listing and editor.
+	if ( isset( $query['wp_id'] ) ) {
+		$wp_query_args['p'] = $query['wp_id'];
+	} else {
+		$wp_query_args['post_status'] = 'publish';
+	}
+
+	$template_query = new WP_Query( $wp_query_args );
+	$query_result   = array();
+	foreach ( $template_query->get_posts() as $post ) {
+		$template = _build_template_result_from_post( $post );
+
+		if ( ! is_wp_error( $template ) ) {
+			$query_result[] = $template;
+		}
+	}
+
+	return $query_result;
+}
+
+/**
+ * Retrieves a single unified template object using its id.
+ *
+ * @since 5.8.0
+ *
+ * @param string $id Template unique identifier (example: theme_slug//template_slug).
+ * @param string $template_type wp_template.
+ *
+ * @return WP_Block_Template|null Template.
+ */
+function get_block_template( $id, $template_type = 'wp_template' ) {
+	$parts = explode( '//', $id, 2 );
+	if ( count( $parts ) < 2 ) {
+		return null;
+	}
+	list( $theme, $slug ) = $parts;
+	$wp_query_args        = array(
+		'post_name__in'  => array( $slug ),
+		'post_type'      => $template_type,
+		'post_status'    => array( 'auto-draft', 'draft', 'publish', 'trash' ),
+		'posts_per_page' => 1,
+		'no_found_rows'  => true,
+		'tax_query'      => array(
+			array(
+				'taxonomy' => 'wp_theme',
+				'field'    => 'name',
+				'terms'    => $theme,
+			),
+		),
+	);
+	$template_query       = new WP_Query( $wp_query_args );
+	$posts                = $template_query->get_posts();
+
+	if ( count( $posts ) > 0 ) {
+		$template = _build_template_result_from_post( $posts[0] );
+
+		if ( ! is_wp_error( $template ) ) {
+			return $template;
+		}
+	}
+
+	return null;
+}

wp-includes/block-template.php

@@ -0,0 +1,228 @@
+<?php
+/**
+ * Block template loader functions.
+ *
+ * @package WordPress
+ */
+
+/**
+ * Find a block template with equal or higher specificity than a given PHP template file.
+ *
+ * Internally, this communicates the block content that needs to be used by the template canvas through a global variable.
+ *
+ * @since 5.8.0
+ *
+ * @param string $template  Path to the template. See locate_template().
+ * @param string $type      Sanitized filename without extension.
+ * @param array  $templates A list of template candidates, in descending order of priority.
+ * @return string The path to the Full Site Editing template canvas file, or the fallback PHP template.
+ */
+function locate_block_template( $template, $type, array $templates ) {
+	global $_wp_current_template_content;
+
+	if ( $template ) {
+		// locate_template() has found a PHP template at the path specified by $template.
+		// That means that we have a fallback candidate if we cannot find a block template
+		// with higher specificity.
+		// Thus, before looking for matching block themes, we shorten our list of candidate
+		// templates accordingly.
+
+		// Locate the index of $template (without the theme directory path) in $templates.
+		$relative_template_path = str_replace(
+			array( get_stylesheet_directory() . '/', get_template_directory() . '/' ),
+			'',
+			$template
+		);
+		$index                  = array_search( $relative_template_path, $templates, true );
+
+		// If the template hiearchy algorithm has successfully located a PHP template file,
+		// we will only consider block templates with higher or equal specificity.
+		$templates = array_slice( $templates, 0, $index + 1 );
+	}
+
+	$block_template = resolve_block_template( $type, $templates );
+
+	if ( $block_template ) {
+		if ( empty( $block_template->content ) && is_user_logged_in() ) {
+			$_wp_current_template_content =
+			sprintf(
+				/* translators: %s: Template title */
+				__( 'Empty template: %s' ),
+				$block_template->title
+			);
+		} elseif ( ! empty( $block_template->content ) ) {
+			$_wp_current_template_content = $block_template->content;
+		}
+		if ( isset( $_GET['_wp-find-template'] ) ) {
+			wp_send_json_success( $block_template );
+		}
+	} else {
+		if ( $template ) {
+			return $template;
+		}
+
+		if ( 'index' === $type ) {
+			if ( isset( $_GET['_wp-find-template'] ) ) {
+				wp_send_json_error( array( 'message' => __( 'No matching template found.' ) ) );
+			}
+		} else {
+			return ''; // So that the template loader keeps looking for templates.
+		}
+	}
+
+	// Add hooks for template canvas.
+	// Add viewport meta tag.
+	add_action( 'wp_head', '_block_template_viewport_meta_tag', 0 );
+
+	// Render title tag with content, regardless of whether theme has title-tag support.
+	remove_action( 'wp_head', '_wp_render_title_tag', 1 );    // Remove conditional title tag rendering...
+	add_action( 'wp_head', '_block_template_render_title_tag', 1 ); // ...and make it unconditional.
+
+	// This file will be included instead of the theme's template file.
+	return ABSPATH . WPINC . '/template-canvas.php';
+}
+
+/**
+ * Return the correct 'wp_template' to render for the request template type.
+ *
+ * @access private
+ * @since 5.8.0
+ *
+ * Accepts an optional $template_hierarchy argument as a hint.
+ *
+ * @param string   $template_type      The current template type.
+ * @param string[] $template_hierarchy (optional) The current template hierarchy, ordered by priority.
+ * @return WP_Block_Template|null template A template object, or null if none could be found.
+ */
+function resolve_block_template( $template_type, $template_hierarchy ) {
+	if ( ! $template_type ) {
+		return null;
+	}
+
+	if ( empty( $template_hierarchy ) ) {
+		$template_hierarchy = array( $template_type );
+	}
+
+	$slugs = array_map(
+		'_strip_template_file_suffix',
+		$template_hierarchy
+	);
+
+	// Find all potential templates 'wp_template' post matching the hierarchy.
+	$query     = array(
+		'theme'    => wp_get_theme()->get_stylesheet(),
+		'slug__in' => $slugs,
+	);
+	$templates = get_block_templates( $query );
+
+	// Order these templates per slug priority.
+	// Build map of template slugs to their priority in the current hierarchy.
+	$slug_priorities = array_flip( $slugs );
+
+	usort(
+		$templates,
+		function ( $template_a, $template_b ) use ( $slug_priorities ) {
+			return $slug_priorities[ $template_a->slug ] - $slug_priorities[ $template_b->slug ];
+		}
+	);
+
+	return count( $templates ) ? $templates[0] : null;
+}
+
+/**
+ * Displays title tag with content, regardless of whether theme has title-tag support.
+ *
+ * @access private
+ * @since 5.8.0
+ *
+ * @see _wp_render_title_tag()
+ */
+function _block_template_render_title_tag() {
+	echo '<title>' . wp_get_document_title() . '</title>' . "\n";
+}
+
+/**
+ * Returns the markup for the current template.
+ *
+ * @access private
+ * @since 5.8.0
+ *
+ * @return string block tempate markup.
+ */
+function get_the_block_template_html() {
+	global $_wp_current_template_content;
+	global $wp_embed;
+
+	if ( ! $_wp_current_template_content ) {
+		if ( is_user_logged_in() ) {
+			return '<h1>' . esc_html__( 'No matching template found' ) . '</h1>';
+		}
+		return;
+	}
+
+	$content = $wp_embed->run_shortcode( $_wp_current_template_content );
+	$content = $wp_embed->autoembed( $content );
+	$content = do_blocks( $content );
+	$content = wptexturize( $content );
+	if ( function_exists( 'wp_filter_content_tags' ) ) {
+		$content = wp_filter_content_tags( $content );
+	} else {
+		$content = wp_make_content_images_responsive( $content );
+	}
+	$content = str_replace( ']]>', ']]&gt;', $content );
+
+	// Wrap block template in .wp-site-blocks to allow for specific descendant styles
+	// (e.g. `.wp-site-blocks > *`).
+	return '<div class="wp-site-blocks">' . $content . '</div>';
+}
+
+/**
+ * Renders a 'viewport' meta tag.
+ *
+ * @access private
+ * @since 5.8.0
+ *
+ * This is hooked into {@see 'wp_head'} to decouple its output from the default template canvas.
+ */
+function _block_template_viewport_meta_tag() {
+	echo '<meta name="viewport" content="width=device-width, initial-scale=1" />' . "\n";
+}
+
+/**
+ * Strips .php or .html suffix from template file names.
+ *
+ * @access private
+ * @since 5.8.0
+ *
+ * @param string $template_file Template file name.
+ * @return string Template file name without extension.
+ */
+function _strip_template_file_suffix( $template_file ) {
+	return preg_replace( '/\.(php|html)$/', '', $template_file );
+}
+
+/**
+ * Removes post details from block context when rendering a block template.
+ *
+ * @access private
+ * @since 5.8.0
+ *
+ * @param array $context Default context.
+ *
+ * @return array Filtered context.
+ */
+function _block_template_render_without_post_block_context( $context ) {
+	/*
+	 * When loading a template directly and not through a page
+	 * that resolves it, the top-level post ID and type context get set to that
+	 * of the template. Templates are just the structure of a site, and
+	 * they should not be available as post context because blocks like Post
+	 * Content would recurse infinitely.
+	 */
+	if ( isset( $context['postType'] ) && 'wp_template' === $context['postType'] ) {
+		unset( $context['postId'] );
+		unset( $context['postType'] );
+	}
+
+	return $context;
+}

wp-includes/class-wp-block-template.php

@@ -0,0 +1,103 @@
+<?php
+/**
+ * Blocks API: WP_Block_Template class
+ *
+ * @package WordPress
+ * @since 5.8.0
+ */
+
+/**
+ * Class representing a block template.
+ *
+ * @since 5.8.0
+ */
+class WP_Block_Template {
+
+	/**
+	 * Type: wp_template.
+	 *
+	 * @since 5.8.0
+	 * @var string
+	 */
+	public $type;
+
+	/**
+	 * Theme.
+	 *
+	 * @since 5.8.0
+	 * @var string
+	 */
+	public $theme;
+
+	/**
+	 * Template slug.
+	 *
+	 * @since 5.8.0
+	 * @var string
+	 */
+	public $slug;
+
+	/**
+	 * Id.
+	 *
+	 * @since 5.8.0
+	 * @var string
+	 */
+	public $id;
+
+	/**
+	 * Title.
+	 *
+	 * @since 5.8.0
+	 * @var string
+	 */
+	public $title = '';
+
+	/**
+	 * Content.
+	 *
+	 * @since 5.8.0
+	 * @var string
+	 */
+	public $content = '';
+
+	/**
+	 * Description.
+	 *
+	 * @since 5.8.0
+	 * @var string
+	 */
+	public $description = '';
+
+	/**
+	 * Source of the content. `theme` and `custom` is used for now.
+	 *
+	 * @since 5.8.0
+	 * @var string
+	 */
+	public $source = 'theme';
+
+	/**
+	 * Post Id.
+	 *
+	 * @since 5.8.0
+	 * @var integer|null
+	 */
+	public $wp_id;
+
+	/**
+	 * Template Status.
+	 *
+	 * @since 5.8.0
+	 * @var string
+	 */
+	public $status;
+
+	/**
+	 * Whether a template is, or is based upon, an existing template file.
+	 *
+	 * @since 5.8.0
+	 * @var boolean
+	 */
+	public $has_theme_file;
+}

wp-includes/class-wp-theme.php

@@ -1182,6 +1182,7 @@ final class WP_Theme implements ArrayAccess {
 	 * Returns the theme's post templates.
 	 *
 	 * @since 4.7.0
+	 * @since 5.8.0 Include block templates.
 	 *
 	 * @return string[] Array of page templates, keyed by filename and post type,
 	 *                  with the value of the translated header name.
@@ -1219,6 +1220,15 @@ final class WP_Theme implements ArrayAccess {
 				}
 			}
 
+			if ( current_theme_supports( 'block-templates' ) ) {
+				$block_templates = get_block_templates( array(), 'wp_template' );
+				foreach ( get_post_types( array( 'public' => true ) ) as $type ) {
+					foreach ( $block_templates as $block_template ) {
+						$post_templates[ $type ][ $block_template->slug ] = $block_template->title;
+					}
+				}
+			}
+
 			$this->cache_add( 'post_templates', $post_templates );
 		}
 

wp-includes/default-filters.php

@@ -555,6 +555,9 @@ add_filter( 'style_loader_src', 'wp_style_loader_src', 10, 2 );
 add_action( 'wp_head', 'wp_maybe_inline_styles', 1 ); // Run for styles enqueued in <head>.
 add_action( 'wp_footer', 'wp_maybe_inline_styles', 1 ); // Run for late-loaded styles in the footer.
 
+add_action( 'admin_footer-post.php', 'wp_add_iframed_editor_assets_html' );
+add_action( 'admin_footer-post-new.php', 'wp_add_iframed_editor_assets_html' );
+
 // Taxonomy.
 add_action( 'init', 'create_initial_taxonomies', 0 ); // Highest priority.
 add_action( 'change_locale', 'create_initial_taxonomies' );
@@ -633,4 +636,9 @@ add_filter( 'user_has_cap', 'wp_maybe_grant_install_languages_cap', 1 );
 add_filter( 'user_has_cap', 'wp_maybe_grant_resume_extensions_caps', 1 );
 add_filter( 'user_has_cap', 'wp_maybe_grant_site_health_caps', 1, 4 );
 
+// Block Templates CPT and Rendering
+add_filter( 'render_block_context', '_block_template_render_without_post_block_context' );
+add_filter( 'pre_wp_unique_post_slug', 'wp_filter_wp_template_unique_post_slug', 10, 5 );
+add_action( 'wp_footer', 'the_block_template_skip_link' );
+
 unset( $filter, $action );

wp-includes/post.php

@@ -310,6 +310,66 @@ function create_initial_post_types() {
 		)
 	);
 
+	register_post_type(
+		'wp_template',
+		array(
+			'labels'                => array(
+				'name'                  => __( 'Templates' ),
+				'singular_name'         => __( 'Template' ),
+				'menu_name'             => _x( 'Templates', 'Admin Menu text' ),
+				'add_new'               => _x( 'Add New', 'Template' ),
+				'add_new_item'          => __( 'Add New Template' ),
+				'new_item'              => __( 'New Template' ),
+				'edit_item'             => __( 'Edit Template' ),
+				'view_item'             => __( 'View Template' ),
+				'all_items'             => __( 'All Templates' ),
+				'search_items'          => __( 'Search Templates' ),
+				'parent_item_colon'     => __( 'Parent Template:' ),
+				'not_found'             => __( 'No templates found.' ),
+				'not_found_in_trash'    => __( 'No templates found in Trash.' ),
+				'archives'              => __( 'Template archives' ),
+				'insert_into_item'      => __( 'Insert into template' ),
+				'uploaded_to_this_item' => __( 'Uploaded to this template' ),
+				'filter_items_list'     => __( 'Filter templates list' ),
+				'items_list_navigation' => __( 'Templates list navigation' ),
+				'items_list'            => __( 'Templates list' ),
+			),
+			'description'           => __( 'Templates to include in your theme.' ),
+			'public'                => false,
+			'has_archive'           => false,
+			'show_ui'               => false,
+			'show_in_menu'          => false,
+			'show_in_admin_bar'     => false,
+			'show_in_rest'          => true,
+			'rewrite'               => false,
+			'rest_base'             => 'templates',
+			'rest_controller_class' => 'WP_REST_Templates_Controller',
+			'capability_type'       => array( 'template', 'templates' ),
+			'capabilities'          => array(
+				'create_posts'           => 'edit_theme_options',
+				'delete_posts'           => 'edit_theme_options',
+				'delete_others_posts'    => 'edit_theme_options',
+				'delete_private_posts'   => 'edit_theme_options',
+				'delete_published_posts' => 'edit_theme_options',
+				'edit_posts'             => 'edit_theme_options',
+				'edit_others_posts'      => 'edit_theme_options',
+				'edit_private_posts'     => 'edit_theme_options',
+				'edit_published_posts'   => 'edit_theme_options',
+				'publish_posts'          => 'edit_theme_options',
+				'read'                   => 'edit_theme_options',
+				'read_private_posts'     => 'edit_theme_options',
+			),
+			'map_meta_cap'          => true,
+			'supports'              => array(
+				'title',
+				'slug',
+				'excerpt',
+				'editor',
+				'revisions',
+			),
+		)
+	);
+
 	register_post_status(
 		'publish',
 		array(

wp-includes/rest-api/endpoints/class-wp-rest-templates-controller.php

@@ -0,0 +1,603 @@
+<?php
+/**
+ * REST API: WP_REST_Templates_Controller class
+ *
+ * @package    WordPress
+ * @subpackage REST_API
+ * @since 5.8.0
+ */
+
+/**
+ * Base Templates REST API Controller.
+ *
+ * @since 5.8.0
+ *
+ * @see WP_REST_Controller
+ */
+class WP_REST_Templates_Controller extends WP_REST_Controller {
+
+	/**
+	 * Post type.
+	 *
+	 * @since 5.8.0
+	 * @var string
+	 */
+	protected $post_type;
+
+	/**
+	 * Constructor.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param string $post_type Post type.
+	 */
+	public function __construct( $post_type ) {
+		$this->post_type = $post_type;
+		$this->namespace = 'wp/v2';
+		$obj             = get_post_type_object( $post_type );
+		$this->rest_base = ! empty( $obj->rest_base ) ? $obj->rest_base : $obj->name;
+	}
+
+	/**
+	 * Registers the controllers routes.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @return void
+	 */
+	public function register_routes() {
+		// Lists all templates.
+		register_rest_route(
+			$this->namespace,
+			'/' . $this->rest_base,
+			array(
+				array(
+					'methods'             => WP_REST_Server::READABLE,
+					'callback'            => array( $this, 'get_items' ),
+					'permission_callback' => array( $this, 'get_items_permissions_check' ),
+					'args'                => $this->get_collection_params(),
+				),
+				array(
+					'methods'             => WP_REST_Server::CREATABLE,
+					'callback'            => array( $this, 'create_item' ),
+					'permission_callback' => array( $this, 'create_item_permissions_check' ),
+					'args'                => $this->get_endpoint_args_for_item_schema( WP_REST_Server::CREATABLE ),
+				),
+				'schema' => array( $this, 'get_public_item_schema' ),
+			)
+		);
+
+		// Lists/updates a single template based on the given id.
+		register_rest_route(
+			$this->namespace,
+			'/' . $this->rest_base . '/(?P<id>[\/\w-]+)',
+			array(
+				array(
+					'methods'             => WP_REST_Server::READABLE,
+					'callback'            => array( $this, 'get_item' ),
+					'permission_callback' => array( $this, 'get_item_permissions_check' ),
+					'args'                => array(
+						'id' => array(
+							'description' => __( 'The id of a template' ),
+							'type'        => 'string',
+						),
+					),
+				),
+				array(
+					'methods'             => WP_REST_Server::EDITABLE,
+					'callback'            => array( $this, 'update_item' ),
+					'permission_callback' => array( $this, 'update_item_permissions_check' ),
+					'args'                => $this->get_endpoint_args_for_item_schema( WP_REST_Server::EDITABLE ),
+				),
+				array(
+					'methods'             => WP_REST_Server::DELETABLE,
+					'callback'            => array( $this, 'delete_item' ),
+					'permission_callback' => array( $this, 'delete_item_permissions_check' ),
+					'args'                => array(
+						'force' => array(
+							'type'        => 'boolean',
+							'default'     => false,
+							'description' => __( 'Whether to bypass Trash and force deletion.' ),
+						),
+					),
+				),
+				'schema' => array( $this, 'get_public_item_schema' ),
+			)
+		);
+	}
+
+	/**
+	 * Checks if the user has permissions to make the request.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @return true|WP_Error True if the request has read access, WP_Error object otherwise.
+	 */
+	protected function permissions_check() {
+		// Verify if the current user has edit_theme_options capability.
+		// This capability is required to edit/view/delete templates.
+		if ( ! current_user_can( 'edit_theme_options' ) ) {
+			return new WP_Error(
+				'rest_cannot_manage_templates',
+				__( 'Sorry, you are not allowed to access the templates on this site.' ),
+				array(
+					'status' => rest_authorization_required_code(),
+				)
+			);
+		}
+
+		return true;
+	}
+
+	/**
+	 * Checks if a given request has access to read templates.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param WP_REST_Request $request Full details about the request.
+	 * @return true|WP_Error True if the request has read access, WP_Error object otherwise.
+	 */
+	public function get_items_permissions_check( $request ) {
+		return $this->permissions_check( $request );
+	}
+
+	/**
+	 * Returns a list of templates.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param WP_REST_Request $request The request instance.
+	 *
+	 * @return WP_REST_Response
+	 */
+	public function get_items( $request ) {
+		$query = array();
+		if ( isset( $request['wp_id'] ) ) {
+			$query['wp_id'] = $request['wp_id'];
+		}
+		if ( isset( $request['area'] ) ) {
+			$query['area'] = $request['area'];
+		}
+		$templates = array();
+		foreach ( get_block_templates( $query, $this->post_type ) as $template ) {
+			$data        = $this->prepare_item_for_response( $template, $request );
+			$templates[] = $this->prepare_response_for_collection( $data );
+		}
+
+		return rest_ensure_response( $templates );
+	}
+
+	/**
+	 * Checks if a given request has access to read a single template.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param WP_REST_Request $request Full details about the request.
+	 * @return true|WP_Error True if the request has read access for the item, WP_Error object otherwise.
+	 */
+	public function get_item_permissions_check( $request ) {
+		return $this->permissions_check( $request );
+	}
+
+	/**
+	 * Returns the given template
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param WP_REST_Request $request The request instance.
+	 *
+	 * @return WP_REST_Response|WP_Error
+	 */
+	public function get_item( $request ) {
+		$template = get_block_template( $request['id'], $this->post_type );
+
+		if ( ! $template ) {
+			return new WP_Error( 'rest_template_not_found', __( 'No templates exist with that id.' ), array( 'status' => 404 ) );
+		}
+
+		return $this->prepare_item_for_response( $template, $request );
+	}
+
+	/**
+	 * Checks if a given request has access to write a single template.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param WP_REST_Request $request Full details about the request.
+	 * @return true|WP_Error True if the request has write access for the item, WP_Error object otherwise.
+	 */
+	public function update_item_permissions_check( $request ) {
+		return $this->permissions_check( $request );
+	}
+
+	/**
+	 * Updates a single template.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param WP_REST_Request $request Full details about the request.
+	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
+	 */
+	public function update_item( $request ) {
+		$template = get_block_template( $request['id'], $this->post_type );
+		if ( ! $template ) {
+			return new WP_Error( 'rest_template_not_found', __( 'No templates exist with that id.' ), array( 'status' => 404 ) );
+		}
+
+		$changes = $this->prepare_item_for_database( $request );
+
+		if ( 'custom' === $template->source ) {
+			$result = wp_update_post( wp_slash( (array) $changes ), true );
+		} else {
+			$result = wp_insert_post( wp_slash( (array) $changes ), true );
+		}
+		if ( is_wp_error( $result ) ) {
+			return $result;
+		}
+
+		$template      = get_block_template( $request['id'], $this->post_type );
+		$fields_update = $this->update_additional_fields_for_object( $template, $request );
+		if ( is_wp_error( $fields_update ) ) {
+			return $fields_update;
+		}
+
+		return $this->prepare_item_for_response(
+			get_block_template( $request['id'], $this->post_type ),
+			$request
+		);
+	}
+
+	/**
+	 * Checks if a given request has access to create a template.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param WP_REST_Request $request Full details about the request.
+	 * @return true|WP_Error True if the request has access to create items, WP_Error object otherwise.
+	 */
+	public function create_item_permissions_check( $request ) {
+		return $this->permissions_check( $request );
+	}
+
+	/**
+	 * Creates a single template.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param WP_REST_Request $request Full details about the request.
+	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
+	 */
+	public function create_item( $request ) {
+		$changes            = $this->prepare_item_for_database( $request );
+		$changes->post_name = $request['slug'];
+		$result             = wp_insert_post( wp_slash( (array) $changes ), true );
+		if ( is_wp_error( $result ) ) {
+			return $result;
+		}
+		$posts = get_block_templates( array( 'wp_id' => $result ), $this->post_type );
+		if ( ! count( $posts ) ) {
+			return new WP_Error( 'rest_template_insert_error', __( 'No templates exist with that id.' ) );
+		}
+		$id            = $posts[0]->id;
+		$template      = get_block_template( $id, $this->post_type );
+		$fields_update = $this->update_additional_fields_for_object( $template, $request );
+		if ( is_wp_error( $fields_update ) ) {
+			return $fields_update;
+		}
+
+		return $this->prepare_item_for_response(
+			get_block_template( $id, $this->post_type ),
+			$request
+		);
+	}
+
+	/**
+	 * Checks if a given request has access to delete a single template.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param WP_REST_Request $request Full details about the request.
+	 * @return true|WP_Error True if the request has delete access for the item, WP_Error object otherwise.
+	 */
+	public function delete_item_permissions_check( $request ) {
+		return $this->permissions_check( $request );
+	}
+
+	/**
+	 * Deletes a single template.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param WP_REST_Request $request Full details about the request.
+	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
+	 */
+	public function delete_item( $request ) {
+		$template = get_block_template( $request['id'], $this->post_type );
+		if ( ! $template ) {
+			return new WP_Error( 'rest_template_not_found', __( 'No templates exist with that id.' ), array( 'status' => 404 ) );
+		}
+		if ( 'custom' !== $template->source ) {
+			return new WP_Error( 'rest_invalid_template', __( 'Templates based on theme files can\'t be removed.' ), array( 'status' => 400 ) );
+		}
+
+		$id    = $template->wp_id;
+		$force = (bool) $request['force'];
+
+		// If we're forcing, then delete permanently.
+		if ( $force ) {
+			$previous = $this->prepare_item_for_response( $template, $request );
+			wp_delete_post( $id, true );
+			$response = new WP_REST_Response();
+			$response->set_data(
+				array(
+					'deleted'  => true,
+					'previous' => $previous->get_data(),
+				)
+			);
+
+			return $response;
+		}
+
+		// Otherwise, only trash if we haven't already.
+		if ( 'trash' === $template->status ) {
+			return new WP_Error(
+				'rest_template_already_trashed',
+				__( 'The template has already been deleted.' ),
+				array( 'status' => 410 )
+			);
+		}
+
+		wp_trash_post( $id );
+		$template->status = 'trash';
+		return $this->prepare_item_for_response( $template, $request );
+	}
+
+	/**
+	 * Prepares a single template for create or update.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param WP_REST_Request $request Request object.
+	 * @return stdClass Changes to pass to wp_update_post.
+	 */
+	protected function prepare_item_for_database( $request ) {
+		$template = $request['id'] ? get_block_template( $request['id'], $this->post_type ) : null;
+		$changes  = new stdClass();
+		if ( null === $template ) {
+			$changes->post_type   = $this->post_type;
+			$changes->post_status = 'publish';
+			$changes->tax_input   = array(
+				'wp_theme' => isset( $request['theme'] ) ? $request['theme'] : wp_get_theme()->get_stylesheet(),
+			);
+		} elseif ( 'custom' !== $template->source ) {
+			$changes->post_name   = $template->slug;
+			$changes->post_type   = $this->post_type;
+			$changes->post_status = 'publish';
+			$changes->tax_input   = array(
+				'wp_theme' => $template->theme,
+			);
+		} else {
+			$changes->post_name   = $template->slug;
+			$changes->ID          = $template->wp_id;
+			$changes->post_status = 'publish';
+		}
+		if ( isset( $request['content'] ) ) {
+			$changes->post_content = $request['content'];
+		} elseif ( null !== $template && 'custom' !== $template->source ) {
+			$changes->post_content = $template->content;
+		}
+		if ( isset( $request['title'] ) ) {
+			$changes->post_title = $request['title'];
+		} elseif ( null !== $template && 'custom' !== $template->source ) {
+			$changes->post_title = $template->title;
+		}
+		if ( isset( $request['description'] ) ) {
+			$changes->post_excerpt = $request['description'];
+		} elseif ( null !== $template && 'custom' !== $template->source ) {
+			$changes->post_excerpt = $template->description;
+		}
+
+		return $changes;
+	}
+
+	/**
+	 * Prepare a single template output for response
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param WP_Block_Template $template Template instance.
+	 * @param WP_REST_Request   $request Request object.
+	 *
+	 * @return WP_REST_Response $data
+	 */
+	public function prepare_item_for_response( $template, $request ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
+		$result = array(
+			'id'             => $template->id,
+			'theme'          => $template->theme,
+			'content'        => array( 'raw' => $template->content ),
+			'slug'           => $template->slug,
+			'source'         => $template->source,
+			'type'           => $template->type,
+			'description'    => $template->description,
+			'title'          => array(
+				'raw'      => $template->title,
+				'rendered' => $template->title,
+			),
+			'status'         => $template->status,
+			'wp_id'          => $template->wp_id,
+			'has_theme_file' => $template->has_theme_file,
+		);
+
+		if ( 'wp_template_part' === $template->type ) {
+			$result['area'] = $template->area;
+		}
+
+		$result = $this->add_additional_fields_to_object( $result, $request );
+
+		$response = rest_ensure_response( $result );
+		$links    = $this->prepare_links( $template->id );
+		$response->add_links( $links );
+		if ( ! empty( $links['self']['href'] ) ) {
+			$actions = $this->get_available_actions();
+			$self    = $links['self']['href'];
+			foreach ( $actions as $rel ) {
+				$response->add_link( $rel, $self );
+			}
+		}
+
+		return $response;
+	}
+
+
+	/**
+	 * Prepares links for the request.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @param integer $id ID.
+	 * @return array Links for the given post.
+	 */
+	protected function prepare_links( $id ) {
+		$base = sprintf( '%s/%s', $this->namespace, $this->rest_base );
+
+		$links = array(
+			'self'       => array(
+				'href' => rest_url( trailingslashit( $base ) . $id ),
+			),
+			'collection' => array(
+				'href' => rest_url( $base ),
+			),
+			'about'      => array(
+				'href' => rest_url( 'wp/v2/types/' . $this->post_type ),
+			),
+		);
+
+		return $links;
+	}
+
+	/**
+	 * Get the link relations available for the post and current user.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @return array List of link relations.
+	 */
+	protected function get_available_actions() {
+		$rels = array();
+
+		$post_type = get_post_type_object( $this->post_type );
+
+		if ( current_user_can( $post_type->cap->publish_posts ) ) {
+			$rels[] = 'https://api.w.org/action-publish';
+		}
+
+		if ( current_user_can( 'unfiltered_html' ) ) {
+			$rels[] = 'https://api.w.org/action-unfiltered-html';
+		}
+
+		return $rels;
+	}
+
+	/**
+	 * Retrieves the query params for the posts collection.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @return array Collection parameters.
+	 */
+	public function get_collection_params() {
+		return array(
+			'context' => $this->get_context_param(),
+			'wp_id'   => array(
+				'description' => __( 'Limit to the specified post id.' ),
+				'type'        => 'integer',
+			),
+		);
+	}
+
+	/**
+	 * Retrieves the block type' schema, conforming to JSON Schema.
+	 *
+	 * @since 5.8.0
+	 *
+	 * @return array Item schema data.
+	 */
+	public function get_item_schema() {
+		if ( $this->schema ) {
+			return $this->add_additional_fields_schema( $this->schema );
+		}
+
+		$schema = array(
+			'$schema'    => 'http://json-schema.org/draft-04/schema#',
+			'title'      => $this->post_type,
+			'type'       => 'object',
+			'properties' => array(
+				'id'             => array(
+					'description' => __( 'ID of template.' ),
+					'type'        => 'string',
+					'context'     => array( 'embed', 'view', 'edit' ),
+					'readonly'    => true,
+				),
+				'slug'           => array(
+					'description' => __( 'Unique slug identifying the template.' ),
+					'type'        => 'string',
+					'context'     => array( 'embed', 'view', 'edit' ),
+					'required'    => true,
+					'minLength'   => 1,
+					'pattern'     => '[a-zA-Z_\-]+',
+				),
+				'theme'          => array(
+					'description' => __( 'Theme identifier for the template.' ),
+					'type'        => 'string',
+					'context'     => array( 'embed', 'view', 'edit' ),
+				),
+				'source'         => array(
+					'description' => __( 'Source of template' ),
+					'type'        => 'string',
+					'context'     => array( 'embed', 'view', 'edit' ),
+					'readonly'    => true,
+				),
+				'content'        => array(
+					'description' => __( 'Content of template.' ),
+					'type'        => array( 'object', 'string' ),
+					'default'     => '',
+					'context'     => array( 'embed', 'view', 'edit' ),
+				),
+				'title'          => array(
+					'description' => __( 'Title of template.' ),
+					'type'        => array( 'object', 'string' ),
+					'default'     => '',
+					'context'     => array( 'embed', 'view', 'edit' ),
+				),
+				'description'    => array(
+					'description' => __( 'Description of template.' ),
+					'type'        => 'string',
+					'default'     => '',
+					'context'     => array( 'embed', 'view', 'edit' ),
+				),
+				'status'         => array(
+					'description' => __( 'Status of template.' ),
+					'type'        => 'string',
+					'default'     => 'publish',
+					'context'     => array( 'embed', 'view', 'edit' ),
+				),
+				'wp_id'          => array(
+					'description' => __( 'Post ID.' ),
+					'type'        => 'integer',
+					'context'     => array( 'embed', 'view', 'edit' ),
+					'readonly'    => true,
+				),
+				'has_theme_file' => array(
+					'description' => __( 'Theme file exists.' ),
+					'type'        => 'bool',
+					'context'     => array( 'embed', 'view', 'edit' ),
+					'readonly'    => true,
+				),
+			),
+		);
+
+		$this->schema = $schema;
+
+		return $this->add_additional_fields_schema( $this->schema );
+	}
+}

wp-includes/script-loader.php

@@ -2662,3 +2662,65 @@ function wp_maybe_inline_styles() {
 		}
 	}
 }
+
+/**
+ * Inject the block editor assets that need to be loaded into the editor's iframe as an inline script.
+ *
+ * @since 5.8.0
+ */
+function wp_add_iframed_editor_assets_html() {
+	$script_handles = array();
+	$style_handles  = array(
+		'wp-block-editor',
+		'wp-block-library',
+		'wp-block-library-theme',
+		'wp-edit-blocks',
+	);
+
+	$block_registry = WP_Block_Type_Registry::get_instance();
+
+	foreach ( $block_registry->get_all_registered() as $block_type ) {
+		if ( ! empty( $block_type->style ) ) {
+			$style_handles[] = $block_type->style;
+		}
+
+		if ( ! empty( $block_type->editor_style ) ) {
+			$style_handles[] = $block_type->editor_style;
+		}
+
+		if ( ! empty( $block_type->script ) ) {
+			$script_handles[] = $block_type->script;
+		}
+	}
+
+	$style_handles = array_unique( $style_handles );
+	$done          = wp_styles()->done;
+
+	ob_start();
+
+	wp_styles()->done = array();
+	wp_styles()->do_items( $style_handles );
+	wp_styles()->done = $done;
+
+	$styles = ob_get_clean();
+
+	$script_handles = array_unique( $script_handles );
+	$done           = wp_scripts()->done;
+
+	ob_start();
+
+	wp_scripts()->done = array();
+	wp_scripts()->do_items( $script_handles );
+	wp_scripts()->done = $done;
+
+	$scripts = ob_get_clean();
+
+	$editor_assets = wp_json_encode(
+		array(
+			'styles'  => $styles,
+			'scripts' => $scripts,
+		)
+	);
+
+	echo "<script>window.__editorAssets = $editor_assets</script>";
+}

wp-includes/taxonomy.php

@@ -172,6 +172,25 @@ function create_initial_taxonomies() {
 			'show_in_nav_menus' => current_theme_supports( 'post-formats' ),
 		)
 	);
+
+	register_taxonomy(
+		'wp_theme',
+		array( 'wp_template' ),
+		array(
+			'public'            => false,
+			'hierarchical'      => false,
+			'labels'            => array(
+				'name'          => __( 'Themes' ),
+				'singular_name' => __( 'Theme' ),
+			),
+			'query_var'         => false,
+			'rewrite'           => false,
+			'show_ui'           => false,
+			'_builtin'          => true,
+			'show_in_nav_menus' => false,
+			'show_in_rest'      => false,
+		)
+	);
 }
 
 /**

wp-includes/template-canvas.php

@@ -0,0 +1,28 @@
+<?php
+/**
+ * Template canvas file to render the current 'wp_template'.
+ *
+ * @package WordPress
+ */
+
+/**
+ * Get the template HTML.
+ * This needs to run before <head> so that blocks can add scripts and styles in wp_head().
+ */
+$template_html = get_the_block_template_html();
+?>
+<!DOCTYPE html>
+<html <?php language_attributes(); ?>>
+<head>
+	<meta charset="<?php bloginfo( 'charset' ); ?>" />
+	<?php wp_head(); ?>
+</head>
+
+<body <?php body_class(); ?>>
+<?php wp_body_open(); ?>
+
+<?php echo $template_html; // phpcs:ignore WordPress.Security.EscapeOutput ?>
+
+<?php wp_footer(); ?>
+</body>
+</html>

wp-includes/template.php

@@ -63,6 +63,8 @@ function get_query_template( $type, $templates = array() ) {
 
 	$template = locate_template( $templates );
 
+	$template = locate_block_template( $template, $type, $templates );
+
 	/**
 	 * Filters the path of the queried template by type.
 	 *

wp-includes/theme-templates.php

@@ -0,0 +1,163 @@
+<?php
+
+/**
+ * Generates a unique slug for templates.
+ *
+ * @access private
+ * @since 5.8.0
+ *
+ * @param string $override_slug The filtered value of the slug (starts as `null` from apply_filter).
+ * @param string $slug          The original/un-filtered slug (post_name).
+ * @param int    $post_ID       Post ID.
+ * @param string $post_status   No uniqueness checks are made if the post is still draft or pending.
+ * @param string $post_type     Post type.
+ * @return string The original, desired slug.
+ */
+function wp_filter_wp_template_unique_post_slug( $override_slug, $slug, $post_ID, $post_status, $post_type ) {
+	if ( 'wp_template' !== $post_type ) {
+		return $override_slug;
+	}
+
+	if ( ! $override_slug ) {
+		$override_slug = $slug;
+	}
+
+	// Template slugs must be unique within the same theme.
+	// TODO - Figure out how to update this to work for a multi-theme
+	// environment.  Unfortunately using `get_the_terms` for the 'wp-theme'
+	// term does not work in the case of new entities since is too early in
+	// the process to have been saved to the entity.  So for now we use the
+	// currently activated theme for creation.
+	$theme = wp_get_theme()->get_stylesheet();
+	$terms = get_the_terms( $post_ID, 'wp_theme' );
+	if ( $terms && ! is_wp_error( $terms ) ) {
+		$theme = $terms[0]->name;
+	}
+
+	$check_query_args = array(
+		'post_name__in'  => array( $override_slug ),
+		'post_type'      => $post_type,
+		'posts_per_page' => 1,
+		'no_found_rows'  => true,
+		'post__not_in'   => array( $post_ID ),
+		'tax_query'      => array(
+			array(
+				'taxonomy' => 'wp_theme',
+				'field'    => 'name',
+				'terms'    => $theme,
+			),
+		),
+	);
+	$check_query      = new WP_Query( $check_query_args );
+	$posts            = $check_query->get_posts();
+
+	if ( count( $posts ) > 0 ) {
+		$suffix = 2;
+		do {
+			$query_args                  = $check_query_args;
+			$alt_post_name               = _truncate_post_slug( $override_slug, 200 - ( strlen( $suffix ) + 1 ) ) . "-$suffix";
+			$query_args['post_name__in'] = array( $alt_post_name );
+			$query                       = new WP_Query( $query_args );
+			$suffix++;
+		} while ( count( $query->get_posts() ) > 0 );
+		$override_slug = $alt_post_name;
+	}
+
+	return $override_slug;
+}
+
+/**
+ * Print the skip-link script & styles.
+ *
+ * @access private
+ * @since 5.8.0
+ *
+ * @return void
+ */
+function the_block_template_skip_link() {
+
+	// Early exit if not an FSE theme.
+	if ( ! current_theme_supports( 'block-templates' ) ) {
+		return;
+	}
+	?>
+
+	<?php
+	/**
+	 * Print the skip-link styles.
+	 */
+	?>
+	<style id="skip-link-styles">
+		.skip-link.screen-reader-text {
+			border: 0;
+			clip: rect(1px,1px,1px,1px);
+			clip-path: inset(50%);
+			height: 1px;
+			margin: -1px;
+			overflow: hidden;
+			padding: 0;
+			position: absolute !important;
+			width: 1px;
+			word-wrap: normal !important;
+		}
+
+		.skip-link.screen-reader-text:focus {
+			background-color: #eee;
+			clip: auto !important;
+			clip-path: none;
+			color: #444;
+			display: block;
+			font-size: 1em;
+			height: auto;
+			left: 5px;
+			line-height: normal;
+			padding: 15px 23px 14px;
+			text-decoration: none;
+			top: 5px;
+			width: auto;
+			z-index: 100000;
+		}
+	</style>
+	<?php
+	/**
+	 * Print the skip-link script.
+	 */
+	?>
+	<script>
+	( function() {
+		var skipLinkTarget = document.querySelector( 'main' ),
+			parentEl,
+			skipLinkTargetID,
+			skipLink;
+
+		// Early exit if a skip-link target can't be located.
+		if ( ! skipLinkTarget ) {
+			return;
+		}
+
+		// Get the site wrapper.
+		// The skip-link will be injected in the beginning of it.
+		parentEl = document.querySelector( '.wp-site-blocks' ) || document.body,
+
+		// Get the skip-link target's ID, and generate one if it doesn't exist.
+		skipLinkTargetID = skipLinkTarget.id;
+		if ( ! skipLinkTargetID ) {
+			skipLinkTargetID = 'wp--skip-link--target';
+			skipLinkTarget.id = skipLinkTargetID;
+		}
+
+		// Create the skip link.
+		skipLink = document.createElement( 'a' );
+		skipLink.classList.add( 'skip-link', 'screen-reader-text' );
+		skipLink.href = '#' + skipLinkTargetID;
+		skipLink.innerHTML = '<?php esc_html_e( 'Skip to content' ); ?>';
+
+		// Inject the skip link.
+		parentEl.insertAdjacentElement( 'afterbegin', skipLink );
+	}() );
+	</script>
+	<?php
+}
+
+// By default, themes support block templates.
+add_theme_support( 'block-templates' );

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.8-alpha-51002';
+$wp_version = '5.8-alpha-51003';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.

wp-settings.php

@@ -170,6 +170,10 @@ require ABSPATH . WPINC . '/query.php';
 require ABSPATH . WPINC . '/class-wp-date-query.php';
 require ABSPATH . WPINC . '/theme.php';
 require ABSPATH . WPINC . '/class-wp-theme.php';
+require ABSPATH . WPINC . '/class-wp-block-template.php';
+require ABSPATH . WPINC . '/block-template-utils.php';
+require ABSPATH . WPINC . '/block-template.php';
+require ABSPATH . WPINC . '/theme-templates.php';
 require ABSPATH . WPINC . '/template.php';
 require ABSPATH . WPINC . '/https-detection.php';
 require ABSPATH . WPINC . '/https-migration.php';
@@ -268,6 +272,7 @@ require ABSPATH . WPINC . '/rest-api/endpoints/class-wp-rest-site-health-control
 require ABSPATH . WPINC . '/rest-api/endpoints/class-wp-rest-sidebars-controller.php';
 require ABSPATH . WPINC . '/rest-api/endpoints/class-wp-rest-widget-types-controller.php';
 require ABSPATH . WPINC . '/rest-api/endpoints/class-wp-rest-widgets-controller.php';
+require ABSPATH . WPINC . '/rest-api/endpoints/class-wp-rest-templates-controller.php';
 require ABSPATH . WPINC . '/rest-api/fields/class-wp-rest-meta-fields.php';
 require ABSPATH . WPINC . '/rest-api/fields/class-wp-rest-comment-meta-fields.php';
 require ABSPATH . WPINC . '/rest-api/fields/class-wp-rest-post-meta-fields.php';