Editor: Update preload paths for post and site editor.

Preloading all blocking requests ensures that the editor canvas becomes responsive quickly and that the browser avoids unnecessary client-side requests.

Props mamaduka, joemcgill, audrasjb, peterwilsoncc.
Fixes #63050.

git-svn-id: https://develop.svn.wordpress.org/trunk@59958 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/edit-form-blocks.php

@@ -53,6 +53,10 @@ $rest_path = rest_get_route_for_post( $post );
 
 $active_theme                   = get_stylesheet();
 $global_styles_endpoint_context = current_user_can( 'edit_theme_options' ) ? 'edit' : 'view';
+$template_lookup_slug           = 'page' === $post->post_type ? 'page' : 'single-' . $post->post_type;
+if ( ! empty( $post->post_name ) ) {
+	$template_lookup_slug .= '-' . $post->post_name;
+}
 // Preload common data.
 $preload_paths = array(
 	'/wp/v2/types?context=view',
@@ -79,6 +83,32 @@ $preload_paths = array(
 	 * Please ensure that the equivalent check is kept in sync with this preload path.
 	 */
 	'/wp/v2/global-styles/' . WP_Theme_JSON_Resolver::get_user_global_styles_post_id() . '?context=' . $global_styles_endpoint_context,
+	// Used by getBlockPatternCategories in useBlockEditorSettings.
+	'/wp/v2/block-patterns/categories',
+	// @see packages/core-data/src/entities.js
+	'/?_fields=' . implode(
+		',',
+		array(
+			'description',
+			'gmt_offset',
+			'home',
+			'name',
+			'site_icon',
+			'site_icon_url',
+			'site_logo',
+			'timezone_string',
+			'url',
+			'page_for_posts',
+			'page_on_front',
+			'show_on_front',
+		)
+	),
+	$paths[] = add_query_arg(
+		'slug',
+		// @see https://github.com/WordPress/gutenberg/blob/e093fefd041eb6cc4a4e7f67b92ab54fd75c8858/packages/core-data/src/private-selectors.ts#L244-L254
+		$template_lookup_slug,
+		'/wp/v2/templates/lookup'
+	),
 );
 
 block_editor_rest_api_preload( $preload_paths, $block_editor_context );

src/wp-admin/site-editor.php

@@ -139,7 +139,15 @@ foreach ( get_default_block_template_types() as $slug => $template_type ) {
 	$indexed_template_types[] = $template_type;
 }
 
-$block_editor_context = new WP_Block_Editor_Context( array( 'name' => 'core/edit-site' ) );
+$context_settings = array( 'name' => 'core/edit-site' );
+
+if ( ! empty( $_GET['postId'] ) && is_numeric( $_GET['postId'] ) ) {
+	$context_settings['post'] = get_post( (int) $_GET['postId'] );
+} elseif ( isset( $_GET['p'] ) && preg_match( '/^\/page\/(\d+)$/', $_GET['p'], $matches ) ) {
+	$context_settings['post'] = get_post( (int) $matches[1] );
+}
+
+$block_editor_context = new WP_Block_Editor_Context( $context_settings );
 $custom_settings      = array(
 	'siteUrl'                   => site_url(),
 	'postsPerPage'              => get_option( 'posts_per_page' ),
@@ -199,8 +207,48 @@ $preload_paths = array(
 		),
 		'GET',
 	),
+	'/wp/v2/settings',
+	array( '/wp/v2/settings', 'OPTIONS' ),
+	// Used by getBlockPatternCategories in useBlockEditorSettings.
+	'/wp/v2/block-patterns/categories',
+	// @see packages/core-data/src/entities.js
+	'/?_fields=' . implode(
+		',',
+		array(
+			'description',
+			'gmt_offset',
+			'home',
+			'name',
+			'site_icon',
+			'site_icon_url',
+			'site_logo',
+			'timezone_string',
+			'url',
+			'page_for_posts',
+			'page_on_front',
+			'show_on_front',
+		)
+	),
 );
 
+if ( $block_editor_context->post ) {
+	$route_for_post = rest_get_route_for_post( $block_editor_context->post );
+	if ( $route_for_post ) {
+		$preload_paths[] = add_query_arg( 'context', 'edit', $route_for_post );
+		if ( 'page' === $block_editor_context->post->post_type ) {
+			$preload_paths[] = add_query_arg(
+				'slug',
+				// @see https://github.com/WordPress/gutenberg/blob/e093fefd041eb6cc4a4e7f67b92ab54fd75c8858/packages/core-data/src/private-selectors.ts#L244-L254
+				empty( $block_editor_context->post->post_name ) ? 'page' : 'page-' . $post->post_name,
+				'/wp/v2/templates/lookup'
+			);
+		}
+	}
+} else {
+	$preload_paths[] = '/wp/v2/templates/lookup?slug=front-page';
+	$preload_paths[] = '/wp/v2/templates/lookup?slug=home';
+}
+
 block_editor_rest_api_preload( $preload_paths, $block_editor_context );
 
 wp_add_inline_script(