Implement speculative prerendering

.phpstorm.meta.php

@@ -85,6 +85,7 @@
 			'remove_transients'            => \Google\Web_Stories\Remove_Transients::class,
 			'web_stories_block'            => \Google\Web_Stories\Block\Web_Stories_Block::class,
 			'injector'                     => \Google\Web_Stories\Infrastructure\Injector::class,
+			'speculation_rules'            => \Google\Web_Stories\Speculation_Rules::class,
 		] )
 	);
 

includes/Admin/Dashboard.php

@@ -35,6 +35,7 @@
 use Google\Web_Stories\Decoder;
 use Google\Web_Stories\Experiments;
 use Google\Web_Stories\Font_Post_Type;
+use Google\Web_Stories\Infrastructure\Conditional;
 use Google\Web_Stories\Integrations\Site_Kit;
 use Google\Web_Stories\Integrations\WooCommerce;
 use Google\Web_Stories\Locale;
@@ -48,7 +49,7 @@
 /**
  * Dashboard class.
  */
-class Dashboard extends Service_Base {
+class Dashboard extends Service_Base implements Conditional {
 
 	/**
 	 * Script handle.
@@ -215,6 +216,7 @@ public function register(): void {
 		add_action( 'admin_enqueue_scripts', [ $this, 'enqueue_assets' ] );
 		add_action( 'admin_notices', [ $this, 'display_link_to_dashboard' ] );
 		add_action( 'load-web-story_page_stories-dashboard', [ $this, 'load_stories_dashboard' ] );
+		add_filter( 'web_stories_speculation_rules', [ $this, 'add_speculation_rules' ] );
 	}
 
 	/**
@@ -573,4 +575,44 @@ public function display_link_to_dashboard(): void {
 		</div>
 		<?php
 	}
+
+	/**
+	 * Add the Speculation Rules for the Dashboard.
+	 *
+	 * @return array<string, array<int, array<string, mixed>>> An array containing prerendering rules.
+	 * @since 1.37.0
+	 */
+	public function add_speculation_rules(): array {
+		$new_story_url  = sprintf(
+			'post-new.php?post_type=%s',
+			$this->story_post_type->get_slug()
+		);
+		$edit_story_url = 'post.php?post=*&action=edit';
+		return [
+			'prerender' => [
+				[
+					'source'    => 'document',
+					'where'     => [
+						'and' => [
+							[
+								'href_matches' => [ $edit_story_url, $new_story_url ],
+							],
+						],
+					],
+					'eagerness' => 'moderate',
+				],
+			],
+		];
+	}
+
+	/**
+	 * Check whether the conditional object is currently needed.
+	 *
+	 * @since 1.37.0
+	 *
+	 * @return bool Whether the conditional object is needed.
+	 */
+	public static function is_needed(): bool {
+		return is_admin();
+	}
 }

includes/Plugin.php

@@ -140,6 +140,7 @@ class Plugin extends ServiceBasedPlugin {
 		'user_preferences'             => User\Preferences::class,
 		'remove_transients'            => Remove_Transients::class,
 		'web_stories_block'            => Block\Web_Stories_Block::class,
+		'speculation_rules'            => Speculation_Rules::class,
 	];
 
 	/**
@@ -192,6 +193,7 @@ protected function get_shared_instances(): array {
 			Settings::class,
 			Stories_Script_Data::class,
 			User\Preferences::class,
+			Admin\Dashboard::class,
 		];
 	}
 

includes/Speculation_Rules.php

@@ -0,0 +1,120 @@
+<?php
+/**
+ * Class Speculation_Rules
+ *
+ * @link      https://github.com/googleforcreators/web-stories-wp
+ *
+ * @copyright 2024 Google LLC
+ * @license   https://www.apache.org/licenses/LICENSE-2.0 Apache License 2.0
+ */
+
+/**
+ * Copyright 2024 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+declare(strict_types = 1);
+
+namespace Google\Web_Stories;
+
+/**
+ * Speculation_Rules class.
+ *
+ * @since 1.37.0
+ */
+class Speculation_Rules extends Service_Base {
+	/**
+	 * Story_Post_Type instance.
+	 *
+	 * @var Story_Post_Type Story_Post_Type instance.
+	 */
+	private Story_Post_Type $story_post_type;
+
+	/**
+	 * Speculation_Rules constructor.
+	 *
+	 * @param Story_Post_Type $story_post_type  Story_Post_Type instance.
+	 */
+	public function __construct( Story_Post_Type $story_post_type ) {
+		$this->story_post_type = $story_post_type;
+	}
+
+	/**
+	 * Runs on instantiation.
+	 */
+	public function register(): void {
+		add_action( 'admin_footer', [ $this, 'print_rules' ] );
+		add_action( 'wp_footer', [ $this, 'print_rules' ] );
+	}
+
+	/**
+	 * Retrieves the prerendering rules for a specific page.
+	 *
+	 * @return array<string, array<int, array<string, mixed>>> An array containing prerendering rules.
+	 */
+	public function get_rules(): array {
+		$rules = [];
+
+		if ( ! is_admin() ) {
+			$view_story_url = sprintf(
+				'/%s/*',
+				$this->story_post_type::REWRITE_SLUG
+			);
+			$archive_url    = Story_Post_Type::REWRITE_SLUG;
+
+			$rules = [
+				'prerender' => [
+					[
+						'source'    => 'document',
+						'where'     => [
+							'and' => [
+								[
+									'href_matches' => [
+										$archive_url,
+										$view_story_url,
+									],
+								],
+							],
+						],
+						'eagerness' => 'moderate',
+					],
+				],
+			];
+		}
+
+		/**
+		 * Filters the prerendering rules.
+		 *
+		 * @param array $rules An array of prerendering rules.
+		 * @since 1.37.0
+		 */
+		return apply_filters( 'web_stories_speculation_rules', $rules );
+	}
+
+	/**
+	 * Prints the prerendering rules as an inline script tag.
+	 */
+	public function print_rules(): void {
+		$rules = $this->get_rules();
+		if ( empty( $rules ) ) {
+			return;
+		}
+
+		$encoded_rules = wp_json_encode( $rules, JSON_UNESCAPED_SLASHES );
+
+		if ( false !== $encoded_rules ) {
+			wp_print_inline_script_tag( $encoded_rules, [ 'type' => 'speculationrules' ] );
+		}
+	}
+}

tests/phpunit/integration/tests/Speculation_Rules.php

@@ -0,0 +1,79 @@
+<?php
+
+declare(strict_types = 1);
+
+/**
+ * Copyright 2020 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+namespace Google\Web_Stories\Tests\Integration;
+
+use Google\Web_Stories\Story_Post_Type;
+
+/**
+ * @coversDefaultClass \Google\Web_Stories\Speculation_Rules
+ */
+class Speculation_Rules extends DependencyInjectedTestCase {
+	private Story_Post_Type $story_post_type;
+
+	protected \Google\Web_Stories\Speculation_Rules $instance;
+
+	public function set_up(): void {
+		parent::set_up();
+
+		$this->story_post_type = $this->injector->make( Story_Post_Type::class );
+
+		$this->instance = new \Google\Web_Stories\Speculation_Rules(
+			$this->story_post_type,
+		);
+	}
+
+	/**
+	 * @covers ::register
+	 */
+	public function test_register(): void {
+		$this->instance->register();
+		$this->assertSame( 10, has_action( 'admin_footer', [ $this->instance, 'print_rules' ] ) );
+		$this->assertSame( 10, has_action( 'wp_footer', [ $this->instance, 'print_rules' ] ) );
+	}
+
+	/**
+	 * @covers ::print_rules
+	 */
+	public function test_print_rules(): void {
+		$expected_rules = [
+			'prerender' => [
+				[
+					'source'    => 'document',
+					'where'     => [
+						'and' => [
+							[ 'href_matches' => [ Story_Post_Type::REWRITE_SLUG, sprintf( '/%s/*', $this->story_post_type::REWRITE_SLUG ) ] ],
+						],
+					],
+					'eagerness' => 'moderate',
+				],
+			],
+		];
+		$output         = get_echo( [ $this->instance, 'print_rules' ] );
+		$this->instance->get_rules();
+
+		$encoded_rules = wp_json_encode( $expected_rules );
+		if ( false !== $encoded_rules ) {
+			$this->assertStringContainsString( $encoded_rules, $output );
+		} else {
+			$this->fail( 'JSON decoding failed.' );
+		}
+	}
+}