Move Speculation Rules to new location as purely a standalone plugin

.github/CODEOWNERS

@@ -57,3 +57,7 @@
 # Plugin: Auto-sizes for Lazy-Loaded Images
 /plugins/auto-sizes                         @joemcgill
 /tests/plugins/auto-sizes                   @joemcgill
+
+# Plugin: Speculation Rules
+/plugins/speculation-rules                  @felixarntz
+/tests/plugins/speculation-rules            @felixarntz

composer.json

@@ -17,6 +17,7 @@
   },
   "require": {
     "composer/installers": "~1.0",
+    "ext-json": "*",
     "php": ">=7|^8"
   },
   "scripts": {
@@ -27,9 +28,11 @@
     "lint": "build-cs/vendor/bin/phpcs",
     "lint:all": [
         "@lint",
-        "@lint:auto-sizes"
+        "@lint:auto-sizes",
+        "@lint:speculation-rules"
     ],
     "lint:auto-sizes": "@lint -- ./plugins/auto-sizes --standard=./plugins/auto-sizes/phpcs.xml.dist",
+    "lint:speculation-rules": "@lint -- ./plugins/speculation-rules --standard=./plugins/speculation-rules/phpcs.xml.dist",
     "test": "phpunit --verbose --testsuite performance-lab",
     "test-multisite": "phpunit -c tests/multisite.xml --verbose --testsuite performance-lab",
     "test:all": [
@@ -41,13 +44,17 @@
       "@test-multisite:plugins"
     ],
     "test:plugins": [
-      "@test:auto-sizes"
+      "@test:auto-sizes",
+      "@test:speculation-rules"
     ],
     "test-multisite:plugins": [
-      "@test-multisite:auto-sizes"
+      "@test-multisite:auto-sizes",
+      "@test-multisite:speculation-rules"
     ],
     "test:auto-sizes": "phpunit --verbose --testsuite auto-sizes",
-    "test-multisite:auto-sizes": "phpunit -c tests/multisite.xml --verbose --testsuite auto-sizes"
+    "test-multisite:auto-sizes": "phpunit -c tests/multisite.xml --verbose --testsuite auto-sizes",
+    "test:speculation-rules": "phpunit --verbose --testsuite speculation-rules",
+    "test-multisite:speculation-rules": "phpunit -c tests/multisite.xml --verbose --testsuite speculation-rules"
   },
   "config": {
     "allow-plugins": {

phpcs.xml.dist

@@ -2,7 +2,7 @@
 <ruleset name="WPP-PerfLab">
 	<description>WordPress Coding Standards for the Performance Lab Plugin</description>
 	<rule ref="phpcs.ruleset.xml"/>
-	
+
 	<config name="text_domain" value="performance-lab,default"/>
 
 	<!-- Do not require file headers on generated files -->

phpunit.xml.dist

@@ -15,6 +15,9 @@
 		<testsuite name="auto-sizes">
 			<directory suffix=".php">./tests/plugins/auto-sizes</directory>
 		</testsuite>
+		<testsuite name="speculation-rules">
+			<directory suffix=".php">./tests/plugins/speculation-rules</directory>
+		</testsuite>
 	</testsuites>
 	<groups>
 		<exclude>

plugins.json

@@ -9,5 +9,8 @@
       "version": "1.0.5"
     }
   },
-  "plugins": [ "auto-sizes" ]
+  "plugins": [
+    "auto-sizes",
+    "speculation-rules"
+  ]
 }

plugins/auto-sizes/auto-sizes.php

@@ -1,7 +1,7 @@
 <?php
 /**
  * Plugin Name: Auto-sizes for Lazy-loaded Images
- * Plugin URI: https://github.com/WordPress/performance/tree/trunk/modules/images/auto-sizes
+ * Plugin URI: https://github.com/WordPress/performance/tree/trunk/plugins/auto-sizes
  * Description: This plugin implements the HTML spec for adding `sizes="auto"` to lazy-loaded images.
  * Requires at least: 6.3
  * Requires PHP: 7.0

plugins/speculation-rules/class-plsr-url-pattern-prefixer.php

@@ -0,0 +1,122 @@
+<?php
+/**
+ * Class 'PLSR_URL_Pattern_Prefixer'.
+ *
+ * @package speculation-rules
+ * @since 1.0.0
+ */
+
+/**
+ * Class for prefixing URL patterns.
+ *
+ * @since 1.0.0
+ */
+class PLSR_URL_Pattern_Prefixer {
+
+	/**
+	 * Map of `$context_string => $base_path` pairs.
+	 *
+	 * @since 1.0.0
+	 * @var array
+	 */
+	private $contexts;
+
+	/**
+	 * Constructor.
+	 *
+	 * @since 1.0.0
+	 *
+	 * @param array $contexts Optional. Map of `$context_string => $base_path` pairs. Default is the contexts returned
+	 *                        by the {@see PLSR_URL_Pattern_Prefixer::get_default_contexts()} method.
+	 */
+	public function __construct( array $contexts = array() ) {
+		if ( $contexts ) {
+			$this->contexts = array_map(
+				static function ( string $str ): string {
+					return self::escape_pattern_string( trailingslashit( $str ) );
+				},
+				$contexts
+			);
+		} else {
+			$this->contexts = self::get_default_contexts();
+		}
+	}
+
+	/**
+	 * Prefixes the given URL path pattern with the base path for the given context.
+	 *
+	 * This ensures that these path patterns work correctly on WordPress subdirectory sites, for example in a multisite
+	 * network, or when WordPress itself is installed in a subdirectory of the hostname.
+	 *
+	 * The given URL path pattern is only prefixed if it does not already include the expected prefix.
+	 *
+	 * @since 1.0.0
+	 *
+	 * @param string $path_pattern URL pattern starting with the path segment.
+	 * @param string $context      Optional. Either 'home' (any frontend content) or 'site' (content relative to the
+	 *                             directory that WordPress is installed in). Default 'home'.
+	 * @return string URL pattern, prefixed as necessary.
+	 */
+	public function prefix_path_pattern( string $path_pattern, string $context = 'home' ): string {
+		// If context path does not exist, the context is invalid.
+		if ( ! isset( $this->contexts[ $context ] ) ) {
+			_doing_it_wrong(
+				__FUNCTION__,
+				esc_html(
+					sprintf(
+						/* translators: %s: context string */
+						__( 'Invalid context %s.', 'speculation-rules' ),
+						$context
+					)
+				),
+				'Performance Lab 1.0.0'
+			);
+			return $path_pattern;
+		}
+
+		// In the event that the context path contains a :, ? or # (which can cause the URL pattern parser to
+		// switch to another state, though only the latter two should be percent encoded anyway), we need to
+		// additionally enclose it in grouping braces. The final forward slash (trailingslashit ensures there is
+		// one) affects the meaning of the * wildcard, so is left outside the braces.
+		$context_path         = $this->contexts[ $context ];
+		$escaped_context_path = $context_path;
+		if ( strcspn( $context_path, ':?#' ) !== strlen( $context_path ) ) {
+			$escaped_context_path = '{' . substr( $context_path, 0, -1 ) . '}/';
+		}
+
+		// If the path already starts with the context path (including '/'), remove it first
+		// since it is about to be added back.
+		if ( str_starts_with( $path_pattern, $context_path ) ) {
+			$path_pattern = substr( $path_pattern, strlen( $context_path ) );
+		}
+
+		return $escaped_context_path . ltrim( $path_pattern, '/' );
+	}
+
+	/**
+	 * Returns the default contexts used by the class.
+	 *
+	 * @since 1.0.0
+	 *
+	 * @return array Map of `$context_string => $base_path` pairs.
+	 */
+	public static function get_default_contexts(): array {
+		return array(
+			'home' => self::escape_pattern_string( trailingslashit( wp_parse_url( home_url( '/' ), PHP_URL_PATH ) ) ),
+			'site' => self::escape_pattern_string( trailingslashit( wp_parse_url( site_url( '/' ), PHP_URL_PATH ) ) ),
+		);
+	}
+
+	/**
+	 * Escapes a string for use in a URL pattern component.
+	 *
+	 * @link https://urlpattern.spec.whatwg.org/#escape-a-pattern-string
+	 * @since 1.0.1
+	 *
+	 * @param string $str String to be escaped.
+	 * @return string String with backslashes added where required.
+	 */
+	private static function escape_pattern_string( string $str ): string {
+		return addcslashes( $str, '+*?:{}()\\' );
+	}
+}