Merge latest changes to feature branch

.github/CODEOWNERS

@@ -32,3 +32,6 @@
 
 # Plugin: Speculative Loading
 /plugins/speculation-rules                  @felixarntz
+
+# Plugin: View Transitions
+/plugins/view-transitions                   @felixarntz

.github/workflows/php-test-plugins.yml

@@ -95,6 +95,7 @@ jobs:
             npm run test-php:image-prioritizer -- -- -- --coverage-clover=./single-site-reports/coverage-image-prioritizer.xml
             npm run test-php:optimization-detective -- -- -- --coverage-clover=./single-site-reports/coverage-optimization-detective.xml
             npm run test-php:speculation-rules -- -- -- --coverage-clover=./single-site-reports/coverage-speculation-rules.xml
+            npm run test-php:view-transitions -- -- -- --coverage-clover=./single-site-reports/coverage-view-transitions.xml
             npm run test-php:web-worker-offloading -- -- -- --coverage-clover=./single-site-reports/coverage-web-worker-offloading.xml
             npm run test-php:webp-uploads -- -- -- --coverage-clover=./single-site-reports/coverage-webp-uploads.xml
           else
@@ -110,6 +111,7 @@ jobs:
             npm run test-php-multisite:image-prioritizer -- -- -- --coverage-clover=./multisite-reports/coverage-multisite-image-prioritizer.xml
             npm run test-php-multisite:optimization-detective -- -- -- --coverage-clover=./multisite-reports/coverage-multisite-optimization-detective.xml
             npm run test-php-multisite:speculation-rules -- -- -- --coverage-clover=./multisite-reports/coverage-multisite-speculation-rules.xml
+            npm run test-php-multisite:view-transitions -- -- -- --coverage-clover=./multisite-reports/coverage-multisite-view-transitions.xml
             npm run test-php-multisite:web-worker-offloading -- -- -- --coverage-clover=./multisite-reports/coverage-multisite-web-worker-offloading.xml
             npm run test-php-multisite:webp-uploads -- -- -- --coverage-clover=./multisite-reports/coverage-multisite-webp-uploads.xml
           else

.wp-env.json

@@ -8,6 +8,7 @@
     "./plugins/image-prioritizer",
     "./plugins/performance-lab",
     "./plugins/speculation-rules",
+    "./plugins/view-transitions",
     "./plugins/web-worker-offloading",
     "./plugins/webp-uploads"
   ],

composer.json

@@ -55,6 +55,7 @@
       "@format:optimization-detective",
       "@format:performance-lab",
       "@format:speculation-rules",
+      "@format:view-transitions",
       "@format:web-worker-offloading",
       "@format:webp-uploads"
     ],
@@ -65,6 +66,7 @@
     "format:optimization-detective": "@format -- ./plugins/optimization-detective --standard=./plugins/optimization-detective/phpcs.xml.dist",
     "format:performance-lab":        "@format -- ./plugins/performance-lab --standard=./plugins/performance-lab/phpcs.xml.dist",
     "format:speculation-rules":      "@format -- ./plugins/speculation-rules --standard=./plugins/speculation-rules/phpcs.xml.dist",
+    "format:view-transitions":       "@format -- ./plugins/view-transitions --standard=./plugins/view-transitions/phpcs.xml.dist",
     "format:web-worker-offloading":  "@format -- ./plugins/web-worker-offloading --standard=./plugins/web-worker-offloading/phpcs.xml.dist",
     "format:webp-uploads":           "@format -- ./plugins/webp-uploads --standard=./plugins/webp-uploads/phpcs.xml.dist",
     "lint": "phpcs",
@@ -77,6 +79,7 @@
       "@lint:optimization-detective",
       "@lint:performance-lab",
       "@lint:speculation-rules",
+      "@lint:view-transitions",
       "@lint:web-worker-offloading",
       "@lint:webp-uploads"
     ],
@@ -87,6 +90,7 @@
     "lint:optimization-detective": "@lint -- ./plugins/optimization-detective --standard=./plugins/optimization-detective/phpcs.xml.dist",
     "lint:performance-lab":        "@lint -- ./plugins/performance-lab --standard=./plugins/performance-lab/phpcs.xml.dist",
     "lint:speculation-rules":      "@lint -- ./plugins/speculation-rules --standard=./plugins/speculation-rules/phpcs.xml.dist",
+    "lint:view-transitions":       "@lint -- ./plugins/view-transitions --standard=./plugins/view-transitions/phpcs.xml.dist",
     "lint:web-worker-offloading":  "@lint -- ./plugins/web-worker-offloading --standard=./plugins/web-worker-offloading/phpcs.xml.dist",
     "lint:webp-uploads":           "@lint -- ./plugins/webp-uploads --standard=./plugins/webp-uploads/phpcs.xml.dist",
     "phpstan": "phpstan analyse --memory-limit=2048M",
@@ -102,6 +106,7 @@
       "@test-multisite:optimization-detective",
       "@test-multisite:performance-lab",
       "@test-multisite:speculation-rules",
+      "@test-multisite:view-transitions",
       "@test-multisite:web-worker-offloading",
       "@test-multisite:webp-uploads"
     ],
@@ -112,6 +117,7 @@
     "test-multisite:optimization-detective": "@test-multisite --verbose --testsuite optimization-detective",
     "test-multisite:performance-lab":        "@test-multisite --verbose --testsuite performance-lab",
     "test-multisite:speculation-rules":      "@test-multisite --verbose --testsuite speculation-rules",
+    "test-multisite:view-transitions":       "@test-multisite --verbose --testsuite view-transitions",
     "test-multisite:web-worker-offloading":  "@test-multisite --verbose --testsuite web-worker-offloading",
     "test-multisite:webp-uploads":           "@test-multisite --verbose --testsuite webp-uploads",
     "test:plugins": [
@@ -122,6 +128,7 @@
       "@test:optimization-detective",
       "@test:performance-lab",
       "@test:speculation-rules",
+      "@test:view-transitions",
       "@test:web-worker-offloading",
       "@test:webp-uploads"
     ],
@@ -132,6 +139,7 @@
     "test:optimization-detective": "@test --verbose --testsuite optimization-detective",
     "test:performance-lab":        "@test --verbose --testsuite performance-lab",
     "test:speculation-rules":      "@test --verbose --testsuite speculation-rules",
+    "test:view-transitions":       "@test --verbose --testsuite view-transitions",
     "test:web-worker-offloading":  "@test --verbose --testsuite web-worker-offloading",
     "test:webp-uploads":           "@test --verbose --testsuite webp-uploads"
   }

package.json

@@ -43,6 +43,7 @@
     "build:plugin:image-prioritizer": "webpack --mode production --env plugin=image-prioritizer",
     "build:plugin:optimization-detective": "webpack --mode production --env plugin=optimization-detective",
     "build:plugin:speculation-rules": "webpack --mode production --env plugin=speculation-rules",
+    "build:plugin:view-transitions": "webpack --mode production --env plugin=view-transitions",
     "build:plugin:web-worker-offloading": "webpack --mode production --env plugin=web-worker-offloading",
     "build:plugin:webp-uploads": "webpack --mode production --env plugin=webp-uploads",
     "generate-pending-release-diffs": "bin/generate-pending-release-diffs.sh",
@@ -62,6 +63,7 @@
     "test-php:image-prioritizer": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:image-prioritizer",
     "test-php:optimization-detective": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:optimization-detective",
     "test-php:speculation-rules": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:speculation-rules",
+    "test-php:view-transitions": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:view-transitions",
     "test-php:web-worker-offloading": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:web-worker-offloading",
     "test-php:webp-uploads": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test:webp-uploads",
     "test-php-multisite:performance-lab": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:performance-lab",
@@ -71,6 +73,7 @@
     "test-php-multisite:image-prioritizer": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:image-prioritizer",
     "test-php-multisite:optimization-detective": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:optimization-detective",
     "test-php-multisite:speculation-rules": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:speculation-rules",
+    "test-php-multisite:view-transitions": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:view-transitions",
     "test-php-multisite:web-worker-offloading": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:web-worker-offloading",
     "test-php-multisite:webp-uploads": "wp-env run tests-cli --env-cwd=/var/www/html/wp-content/plugins/performance composer test-multisite:webp-uploads",
     "wp-env": "wp-env",

phpunit.xml.dist

@@ -29,6 +29,9 @@
 		<testsuite name="speculation-rules">
 			<directory suffix=".php">plugins/speculation-rules/tests</directory>
 		</testsuite>
+		<testsuite name="view-transitions">
+			<directory suffix=".php">plugins/view-transitions/tests</directory>
+		</testsuite>
 		<testsuite name="web-worker-offloading">
 			<directory suffix=".php">plugins/web-worker-offloading/tests</directory>
 		</testsuite>

plugins/view-transitions/hooks.php

@@ -0,0 +1,32 @@
+<?php
+/**
+ * Hook callbacks used for View Transitions.
+ *
+ * @package view-transitions
+ * @since 1.0.0
+ */
+
+// @codeCoverageIgnoreStart
+if ( ! defined( 'ABSPATH' ) ) {
+	exit; // Exit if accessed directly.
+}
+// @codeCoverageIgnoreEnd
+
+/**
+ * Displays the HTML generator tag for the plugin.
+ *
+ * See {@see 'wp_head'}.
+ *
+ * @since 1.0.0
+ */
+function plvt_render_generator(): void {
+	// Use the plugin slug as it is immutable.
+	echo '<meta name="generator" content="view-transitions ' . esc_attr( VIEW_TRANSITIONS_VERSION ) . '">' . "\n";
+}
+add_action( 'wp_head', 'plvt_render_generator' );
+
+/**
+ * Filters related to the View Transitions functionality.
+ */
+add_action( 'after_setup_theme', 'plvt_polyfill_theme_support', PHP_INT_MAX );
+add_action( 'wp_enqueue_scripts', 'plvt_load_view_transitions' );

plugins/view-transitions/includes/theme.php

@@ -0,0 +1,45 @@
+<?php
+/**
+ * Theme related functions for View Transitions.
+ *
+ * @package view-transitions
+ * @since 1.0.0
+ */
+
+/**
+ * Polyfills theme support for 'view-transitions', regardless of the theme.
+ *
+ * In WordPress Core, the 'view-transitions' feature may end up as an optional feature, or it may be added by default.
+ * In any case, in the scope of the plugin it does not make sense to have the feature as opt-in, since it is the entire
+ * purpose of the plugin.
+ *
+ * Therefore, this function will unconditionally add support with the default configuration, unless the theme itself
+ * actually added support for it already.
+ *
+ * This function must run at the latest possible priority for `after_setup_theme`.
+ *
+ * @since 1.0.0
+ */
+function plvt_polyfill_theme_support(): void {
+	if ( current_theme_supports( 'view-transitions' ) ) {
+		return;
+	}
+	add_theme_support( 'view-transitions' );
+}
+
+/**
+ * Loads view transitions based on the current configuration.
+ *
+ * @since 1.0.0
+ */
+function plvt_load_view_transitions(): void {
+	if ( ! current_theme_supports( 'view-transitions' ) ) {
+		return;
+	}
+
+	// Use an inline style to avoid an extra request.
+	$stylesheet = '@view-transition { navigation: auto; }';
+	wp_register_style( 'wp-view-transitions', false, array(), null ); // phpcs:ignore WordPress.WP.EnqueuedResourceParameters.MissingVersion
+	wp_add_inline_style( 'wp-view-transitions', $stylesheet );
+	wp_enqueue_style( 'wp-view-transitions' );
+}

plugins/view-transitions/phpcs.xml.dist

@@ -0,0 +1,10 @@
+<?xml version="1.0"?>
+<ruleset name="WPP-ViewTransitions">
+	<description>WordPress Coding Standards for View Transitions Plugin</description>
+
+	<rule ref="../../tools/phpcs/phpcs.ruleset.xml"/>
+
+	<config name="text_domain" value="view-transitions"/>
+
+	<file>.</file>
+</ruleset>

plugins/view-transitions/readme.txt

@@ -0,0 +1,56 @@
+=== View Transitions ===
+
+Contributors: wordpressdotorg
+Tested up to: 6.8
+Stable tag:   1.4.0
+License:      GPLv2 or later
+License URI:  https://www.gnu.org/licenses/gpl-2.0.html
+Tags:         performance, view transitions, smooth transitions, animations
+
+Adds smooth transitions between navigations to your WordPress site.
+
+== Description ==
+
+This plugin implements support for [cross-document view transitions](https://developer.chrome.com/docs/web-platform/view-transitions/cross-document) in WordPress. This effectively replaces the hard transitions when navigating from one URL to the other with a smooth animation, by default using a fade effect.
+
+= Browser support =
+
+Cross-document view transitions are supported in a variety of browsers, including Chrome, Edge, and Safari. Users with browsers that currently do not support it should not see any adverse effects when the plugin is active. They will simply not benefit from the feature and continue to experience the traditional hard transitions between URLs.
+
+[Please refer to "Can I use..." for a comprehensive overview of browser support for the feature.](https://caniuse.com/mdn-css_at-rules_view-transition)
+
+== Installation ==
+
+= Installation from within WordPress =
+
+1. Visit **Plugins > Add New**.
+2. Search for **View Transitions**.
+3. Install and activate the **View Transitions** plugin.
+
+= Manual installation =
+
+1. Upload the entire plugin folder to the `/wp-content/plugins/` directory.
+2. Visit **Plugins**.
+3. Activate the **View Transitions** plugin.
+
+== Frequently Asked Questions ==
+
+= Where can I submit my plugin feedback? =
+
+Feedback is encouraged and much appreciated, especially since this plugin may contain future WordPress core features. If you have suggestions or requests for new features, you can [submit them as an issue in the WordPress Performance Team's GitHub repository](https://github.com/WordPress/performance/issues/new/choose). If you need help with troubleshooting or have a question about the plugin, please [create a new topic on our support forum](https://wordpress.org/support/plugin/view-transitions/#new-topic-0).
+
+= Where can I report security bugs? =
+
+The Performance team and WordPress community take security bugs seriously. We appreciate your efforts to responsibly disclose your findings, and will make every effort to acknowledge your contributions.
+
+To report a security issue, please visit the [WordPress HackerOne](https://hackerone.com/wordpress) program.
+
+= How can I contribute to the plugin? =
+
+Contributions are always welcome! Learn more about how to get involved in the [Core Performance Team Handbook](https://make.wordpress.org/performance/handbook/get-involved/).
+
+== Changelog ==
+
+= 1.0.0 =
+
+* Initial release.

plugins/view-transitions/tests/test-hooks.php

@@ -0,0 +1,22 @@
+<?php
+/**
+ * Tests for the View Transitions plugin hooks.php file.
+ *
+ * @package view-transitions
+ * @group   view-transitions
+ */
+
+class Test_ViewTransitions_Hooks extends WP_UnitTestCase {
+
+	public function test_hooks(): void {
+		$this->assertSame( 10, has_action( 'wp_head', 'plvt_render_generator' ) );
+		$this->assertSame( PHP_INT_MAX, has_action( 'after_setup_theme', 'plvt_polyfill_theme_support' ) );
+		$this->assertSame( 10, has_action( 'wp_enqueue_scripts', 'plvt_load_view_transitions' ) );
+	}
+
+	public function test_plvt_render_generator(): void {
+		$expected = '<meta name="generator" content="view-transitions ' . VIEW_TRANSITIONS_VERSION . '">' . "\n";
+		$output   = get_echo( 'plvt_render_generator' );
+		$this->assertSame( $expected, $output );
+	}
+}