I18N: Add translation support for script modules

src/wp-includes/class-wp-script-modules.php

@@ -81,6 +81,17 @@ class WP_Script_Modules {
 	 */
 	private $modules_with_missing_dependencies = array();
 
+	/**
+	 * Holds translation data for script modules, keyed by script module identifier.
+	 *
+	 * Each entry contains 'domain' and 'path' keys for the text domain
+	 * and the path to translation files respectively.
+	 *
+	 * @since 7.0.0
+	 * @var array<string, array{domain: string, path: string}>
+	 */
+	private array $translations = array();
+
 	/**
 	 * Registers the script module if no script module with that script module
 	 * identifier has already been registered.
@@ -328,6 +339,80 @@ public function deregister( string $id ) {
 		unset( $this->registered[ $id ] );
 	}
 
+	/**
+	 * Sets translated strings for a script module.
+	 *
+	 * Works similar to {@see WP_Scripts::set_translations()} but for script modules.
+	 * The translations will be loaded and output as inline scripts before
+	 * the script modules are printed, calling `wp.i18n.setLocaleData()`.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $id     The identifier of the script module.
+	 * @param string $domain Optional. Text domain. Default 'default'.
+	 * @param string $path   Optional. The full file path to the directory containing translation files.
+	 * @return bool True if the text domain was registered, false if the module is not registered.
+	 */
+	public function set_translations( string $id, string $domain = 'default', string $path = '' ): bool {
+		if ( ! isset( $this->registered[ $id ] ) ) {
+			return false;
+		}
+
+		$this->translations[ $id ] = array(
+			'domain' => $domain,
+			'path'   => $path,
+		);
+
+		return true;
+	}
+
+	/**
+	 * Prints translations for all enqueued script modules that have translations set.
+	 *
+	 * Outputs inline `<script>` tags that call `wp.i18n.setLocaleData()` with
+	 * the translated strings for each script module. This must run before
+	 * the script modules execute.
+	 *
+	 * @since 7.0.0
+	 */
+	public function print_script_module_translations(): void {
+		// Collect all module IDs that will be on the page (enqueued + their dependencies).
+		$module_ids = $this->get_sorted_dependencies( $this->queue );
+
+		foreach ( $module_ids as $id ) {
+			if ( ! isset( $this->translations[ $id ] ) ) {
+				continue;
+			}
+
+			$domain = $this->translations[ $id ]['domain'];
+			$path   = $this->translations[ $id ]['path'];
+
+			$json_translations = load_script_module_textdomain( $id, $domain, $path );
+
+			if ( ! $json_translations ) {
+				continue;
+			}
+
+			$set_local_data_js_function = <<<JS
+			( domain, translations ) => {
+				const localeData = translations.locale_data[ domain ] || translations.locale_data.messages;
+				localeData[""].domain = domain;
+				wp.i18n.setLocaleData( localeData, domain );
+			}
+			JS;
+
+			$output     = sprintf(
+				'( %s )( %s, %s );',
+				$set_local_data_js_function,
+				wp_json_encode( $domain ),
+				$json_translations
+			);
+			$source_url = rawurlencode( "{$id}-js-module-translations" );
+			$output    .= "\n//# sourceURL={$source_url}";
+			wp_print_inline_script_tag( $output, array( 'id' => "{$id}-js-module-translations" ) );
+		}
+	}
+
 	/**
 	 * Adds the hooks to print the import map, enqueued script modules and script
 	 * module preloads.
@@ -359,6 +444,15 @@ public function add_hooks() {
 		add_action( 'admin_print_footer_scripts', array( $this, 'print_enqueued_script_modules' ) );
 		add_action( 'admin_print_footer_scripts', array( $this, 'print_script_module_preloads' ) );
 
+		/*
+		 * Print translations after classic scripts like wp-i18n are loaded (at
+		 * priority 10 via _wp_footer_scripts), but before the script modules
+		 * execute. Script modules with type="module" are deferred by default,
+		 * so inline translation scripts at priority 11 will execute before them.
+		 */
+		add_action( 'wp_footer', array( $this, 'print_script_module_translations' ), 21 );
+		add_action( 'admin_print_footer_scripts', array( $this, 'print_script_module_translations' ), 11 );
+
 		add_action( 'wp_footer', array( $this, 'print_script_module_data' ) );
 		add_action( 'admin_print_footer_scripts', array( $this, 'print_script_module_data' ) );
 		add_action( 'wp_footer', array( $this, 'print_a11y_script_module_html' ), 20 );
@@ -840,6 +934,22 @@ private function sort_item_dependencies( string $id, array $import_types, array
 		return true;
 	}
 
+	/**
+	 * Gets the raw source URL for a registered script module.
+	 *
+	 * Returns the source URL without version query string appended.
+	 * This is used by {@see load_script_module_textdomain()} to determine
+	 * the relative path for loading translation files.
+	 *
+	 * @since 7.0.0
+	 *
+	 * @param string $id The script module identifier.
+	 * @return string|null The script module source URL, or null if not registered.
+	 */
+	public function get_registered_src( string $id ): ?string {
+		return $this->registered[ $id ]['src'] ?? null;
+	}
+
 	/**
 	 * Gets the versioned URL for a script module src.
 	 *

src/wp-includes/l10n.php

@@ -1134,24 +1134,51 @@ function load_child_theme_textdomain( $domain, $path = false ) {
  *
  * @see WP_Scripts::set_translations()
  *
- * @global WP_Textdomain_Registry $wp_textdomain_registry WordPress Textdomain Registry.
- *
  * @param string $handle Name of the script to register a translation domain to.
  * @param string $domain Optional. Text domain. Default 'default'.
  * @param string $path   Optional. The full file path to the directory containing translation files.
  * @return string|false The translated strings in JSON encoding on success,
  *                      false if the script textdomain could not be loaded.
  */
 function load_script_textdomain( $handle, $domain = 'default', $path = '' ) {
-	/** @var WP_Textdomain_Registry $wp_textdomain_registry */
-	global $wp_textdomain_registry;
-
 	$wp_scripts = wp_scripts();
 
 	if ( ! isset( $wp_scripts->registered[ $handle ] ) ) {
 		return false;
 	}
 
+	$src = $wp_scripts->registered[ $handle ]->src;
+
+	if ( ! preg_match( '|^(https?:)?//|', $src ) && ! ( $wp_scripts->content_url && str_starts_with( $src, $wp_scripts->content_url ) ) ) {
+		$src = $wp_scripts->base_url . $src;
+	}
+
+	return _load_script_textdomain_from_src( $handle, $src, $domain, $path, false );
+}
+
+/**
+ * Resolves and loads the translation JSON file for a given script or script module source URL.
+ *
+ * This is a shared implementation used by {@see load_script_textdomain()} and
+ * {@see load_script_module_textdomain()} to avoid duplicating the path
+ * resolution and file lookup logic.
+ *
+ * @since 7.0.0
+ * @access private
+ *
+ * @global WP_Textdomain_Registry $wp_textdomain_registry WordPress Textdomain Registry.
+ *
+ * @param string $handle    Name of the script or script module identifier to register a translation domain to.
+ * @param string $src       Absolute source URL of the script or script module.
+ * @param string $domain    Text domain.
+ * @param string $path      The full file path to the directory containing translation files,
+ *                          or an empty string to use the default path from the text domain registry.
+ * @param bool   $is_module Whether the source belongs to a script module (true) or a classic script (false).
+ * @return string|false The JSON-encoded translated strings on success, false otherwise.
+ */
+function _load_script_textdomain_from_src( string $handle, string $src, string $domain, string $path, bool $is_module ) {
+	global $wp_textdomain_registry;
+
 	$locale = determine_locale();
 
 	if ( ! $path ) {
@@ -1172,12 +1199,6 @@ function load_script_textdomain( $handle, $domain = 'default', $path = '' ) {
 		}
 	}
 
-	$src = $wp_scripts->registered[ $handle ]->src;
-
-	if ( ! preg_match( '|^(https?:)?//|', $src ) && ! ( $wp_scripts->content_url && str_starts_with( $src, $wp_scripts->content_url ) ) ) {
-		$src = $wp_scripts->base_url . $src;
-	}
-
 	$relative       = false;
 	$languages_path = WP_LANG_DIR;
 
@@ -1245,11 +1266,13 @@ function load_script_textdomain( $handle, $domain = 'default', $path = '' ) {
 	 * Filters the relative path of scripts used for finding translation files.
 	 *
 	 * @since 5.0.2
+	 * @since 7.0.0 The `$is_module` parameter was added.
 	 *
-	 * @param string|false $relative The relative path of the script. False if it could not be determined.
-	 * @param string       $src      The full source URL of the script.
+	 * @param string|false $relative  The relative path of the script. False if it could not be determined.
+	 * @param string       $src       The full source URL of the script.
+	 * @param bool         $is_module Whether the source belongs to a script module (true) or a classic script (false).
 	 */
-	$relative = apply_filters( 'load_script_textdomain_relative_path', $relative, $src );
+	$relative = apply_filters( 'load_script_textdomain_relative_path', $relative, $src, $is_module );
 
 	// If the source is not from WP.
 	if ( false === $relative ) {
@@ -1280,6 +1303,35 @@ function load_script_textdomain( $handle, $domain = 'default', $path = '' ) {
 	return load_script_translations( false, $handle, $domain );
 }
 
+/**
+ * Loads the translation data for a given script module ID and text domain.
+ *
+ * Works like {@see load_script_textdomain()} but for script modules registered
+ * via {@see wp_register_script_module()}.
+ *
+ * @since 7.0.0
+ *
+ * @param string $id     The script module identifier.
+ * @param string $domain Optional. Text domain. Default 'default'.
+ * @param string $path   Optional. The full file path to the directory containing translation files.
+ * @return string|false The JSON-encoded translated strings for the given script module and text domain.
+ *                      False if there are none.
+ */
+function load_script_module_textdomain( string $id, string $domain = 'default', string $path = '' ) {
+	$src = wp_script_modules()->get_registered_src( $id );
+
+	if ( null === $src ) {
+		return false;
+	}
+
+	// Ensure src is an absolute URL for path resolution.
+	if ( ! preg_match( '|^(https?:)?//|', $src ) ) {
+		$src = site_url( $src );
+	}
+
+	return _load_script_textdomain_from_src( $id, $src, $domain, $path, true );
+}
+
 /**
  * Loads the translation data for the given script handle and text domain.
  *

src/wp-includes/script-modules.php

@@ -138,6 +138,25 @@ function wp_deregister_script_module( string $id ) {
 	wp_script_modules()->deregister( $id );
 }
 
+/**
+ * Sets translated strings for a script module.
+ *
+ * Works similar to {@see wp_set_script_translations()} but for script modules
+ * registered via {@see wp_register_script_module()}.
+ *
+ * @since 7.0.0
+ *
+ * @see WP_Script_Modules::set_translations()
+ *
+ * @param string $id     The identifier of the script module.
+ * @param string $domain Optional. Text domain. Default 'default'.
+ * @param string $path   Optional. The full file path to the directory containing translation files.
+ * @return bool True if the text domain was successfully localized, false otherwise.
+ */
+function wp_set_script_module_translations( string $id, string $domain = 'default', string $path = '' ): bool {
+	return wp_script_modules()->set_translations( $id, $domain, $path );
+}
+
 /**
  * Registers all the default WordPress Script Modules.
  *
@@ -197,6 +216,11 @@ function wp_default_script_modules() {
 		$path        = includes_url( "js/dist/script-modules/{$file_name}" );
 		$module_deps = $script_module_data['module_dependencies'] ?? array();
 		wp_register_script_module( $script_module_id, $path, $module_deps, $script_module_data['version'], $args );
+
+		// Set up translations for script modules that use wp-i18n.
+		if ( isset( $script_module_data['dependencies'] ) && in_array( 'wp-i18n', $script_module_data['dependencies'], true ) ) {
+			wp_set_script_module_translations( $script_module_id, 'default' );
+		}
 	}
 
 	wp_register_script_module(