I18N: Support loading .l10n.php translation files on their own.

Adjusts the translation file lookup in `WP_Textdomain_Registry` so that just-in-time translation loading
works even if there is only a `.l10n.php` translation file without a corresponding `.mo` file.

While language packs continue to contain both file types, this makes it easier to use translations in a project
without having to deal with `.mo` or `.po` files.

Props Chrystl.
See #59656.

git-svn-id: https://develop.svn.wordpress.org/trunk@57516 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/class-wp-textdomain-registry.php

@@ -150,21 +150,21 @@ class WP_Textdomain_Registry {
 	}
 
 	/**
-	 * Retrieves .mo files from the specified path.
+	 * Retrieves translation files from the specified path.
 	 *
 	 * Allows early retrieval through the {@see 'pre_get_mo_files_from_path'} filter to optimize
 	 * performance, especially in directories with many files.
 	 *
 	 * @since 6.5.0
 	 *
-	 * @param string $path The directory path to search for .mo files.
-	 * @return array Array of .mo file paths.
+	 * @param string $path The directory path to search for translation files.
+	 * @return array Array of translation file paths. Can contain .mo and .l10n.php files.
 	 */
 	public function get_language_files_from_path( $path ) {
 		$path = rtrim( $path, '/' ) . '/';
 
 		/**
-		 * Filters the .mo files retrieved from a specified path before the actual lookup.
+		 * Filters the translation files retrieved from a specified path before the actual lookup.
 		 *
 		 * Returning a non-null value from the filter will effectively short-circuit
 		 * the MO files lookup, returning that value instead.
@@ -174,27 +174,33 @@ class WP_Textdomain_Registry {
 		 *
 		 * @since 6.5.0
 		 *
-		 * @param null|array $mo_files List of .mo files. Default null.
-		 * @param string $path The path from which .mo files are being fetched.
+		 * @param null|array $files List of translation files. Default null.
+		 * @param string $path The path from which translation files are being fetched.
 		 **/
-		$mo_files = apply_filters( 'pre_get_language_files_from_path', null, $path );
+		$files = apply_filters( 'pre_get_language_files_from_path', null, $path );
 
-		if ( null !== $mo_files ) {
-			return $mo_files;
+		if ( null !== $files ) {
+			return $files;
 		}
 
 		$cache_key = 'cached_mo_files_' . md5( $path );
-		$mo_files  = wp_cache_get( $cache_key, 'translations' );
+		$files     = wp_cache_get( $cache_key, 'translations' );
 
-		if ( false === $mo_files ) {
-			$mo_files = glob( $path . '*.mo' );
-			if ( false === $mo_files ) {
-				$mo_files = array();
+		if ( false === $files ) {
+			$files = glob( $path . '*.mo' );
+			if ( false === $files ) {
+				$files = array();
 			}
-			wp_cache_set( $cache_key, $mo_files, 'translations' );
+
+			$php_files = glob( $path . '*.l10n.php' );
+			if ( is_array( $php_files ) ) {
+				$files = array_merge( $files, $php_files );
+			}
+
+			wp_cache_set( $cache_key, $files, 'translations' );
 		}
 
-		return $mo_files;
+		return $files;
 	}
 
 	/**
@@ -295,17 +301,18 @@ class WP_Textdomain_Registry {
 		foreach ( $locations as $location ) {
 			$files = $this->get_language_files_from_path( $location );
 
-			$path = "$location/$domain-$locale.mo";
+			$mo_path  = "$location/$domain-$locale.mo";
+			$php_path = "$location/$domain-$locale.l10n.php";
 
-			foreach ( $files as $mo_path ) {
+			foreach ( $files as $file_path ) {
 				if (
 					! in_array( $domain, $this->domains_with_translations, true ) &&
-					str_starts_with( str_replace( "$location/", '', $mo_path ), "$domain-" )
+					str_starts_with( str_replace( "$location/", '', $file_path ), "$domain-" )
 				) {
 					$this->domains_with_translations[] = $domain;
 				}
 
-				if ( $mo_path === $path ) {
+				if ( $file_path === $mo_path || $file_path === $php_path ) {
 					$found_location = rtrim( $location, '/' ) . '/';
 				}
 			}

src/wp-includes/l10n.php

@@ -789,10 +789,6 @@ function load_textdomain( $domain, $mofile, $locale = null ) {
 	 */
 	$mofile = apply_filters( 'load_textdomain_mofile', $mofile, $domain );
 
-	if ( ! is_readable( $mofile ) ) {
-		return false;
-	}
-
 	if ( ! $locale ) {
 		$locale = determine_locale();
 	}
@@ -817,14 +813,14 @@ function load_textdomain( $domain, $mofile, $locale = null ) {
 		$preferred_format = 'php';
 	}
 
-	$translation_files = array( $mofile );
+	$translation_files = array();
+
 	if ( 'mo' !== $preferred_format ) {
-		array_unshift(
-			$translation_files,
-			substr_replace( $mofile, ".l10n.$preferred_format", - strlen( '.mo' ) )
-		);
+		$translation_files[] = substr_replace( $mofile, ".l10n.$preferred_format", - strlen( '.mo' ) );
 	}
 
+	$translation_files[] = $mofile;
+
 	foreach ( $translation_files as $file ) {
 		/**
 		 * Filters the file path for loading translations for the given text domain.
@@ -857,7 +853,7 @@ function load_textdomain( $domain, $mofile, $locale = null ) {
 		}
 	}
 
-	return true;
+	return false;
 }
 
 /**

tests/phpunit/data/languages/plugins/internationalized-plugin-2-de_DE.l10n.php

@@ -0,0 +1,2 @@
+<?php
+return ['domain'=>NULL,'plural-forms'=>'nplurals=2; plural=(n != 1);','messages'=>['This is a dummy plugin'=>'Das ist ein Dummy Plugin'],'language'=>'de_DE','x-generator'=>'Poedit 2.4.1'];

tests/phpunit/data/languages/plugins/internationalized-plugin-2-es_ES.l10n.php

@@ -0,0 +1,2 @@
+<?php
+return ['domain'=>NULL,'plural-forms'=>'nplurals=2; plural=(n != 1);','messages'=>['This is a dummy plugin'=>'Este es un plugin dummy'],'language'=>'de_DE','x-generator'=>'Poedit 2.4.1'];

tests/phpunit/data/plugins/internationalized-plugin-2.php

@@ -0,0 +1,12 @@
+<?php
+/*
+Plugin Name: Dummy Plugin 2
+Plugin URI: https://wordpress.org/
+Description: For testing purposes only. Only has an .l10n.php translation file.
+Version: 1.0.0
+Text Domain: internationalized-plugin
+*/
+
+function i18n_plugin_2_test() {
+	return __( 'This is a dummy plugin', 'internationalized-plugin-2' );
+}

tests/phpunit/tests/l10n/loadTextdomainJustInTime.php

@@ -49,6 +49,7 @@ class Tests_L10n_LoadTextdomainJustInTime extends WP_UnitTestCase {
 		$wp_textdomain_registry = new WP_Textdomain_Registry();
 
 		unload_textdomain( 'internationalized-plugin' );
+		unload_textdomain( 'internationalized-plugin-2' );
 		unload_textdomain( 'internationalized-theme' );
 
 		parent::tear_down();
@@ -86,6 +87,27 @@ class Tests_L10n_LoadTextdomainJustInTime extends WP_UnitTestCase {
 		$this->assertTrue( $is_textdomain_loaded_after );
 	}
 
+	/**
+	 * @ticket 59656
+	 *
+	 * @covers ::is_textdomain_loaded
+	 */
+	public function test_plugin_translation_should_be_translated_with_only_an_l10n_php_file() {
+		add_filter( 'locale', array( $this, 'filter_set_locale_to_german' ) );
+
+		require_once DIR_TESTDATA . '/plugins/internationalized-plugin-2.php';
+
+		$is_textdomain_loaded_before = is_textdomain_loaded( 'internationalized-plugin-2' );
+		$actual_output               = i18n_plugin_2_test();
+		$is_textdomain_loaded_after  = is_textdomain_loaded( 'internationalized-plugin-2' );
+
+		remove_filter( 'locale', array( $this, 'filter_set_locale_to_german' ) );
+
+		$this->assertFalse( $is_textdomain_loaded_before );
+		$this->assertSame( 'Das ist ein Dummy Plugin', $actual_output );
+		$this->assertTrue( $is_textdomain_loaded_after );
+	}
+
 	/**
 	 * @ticket 34114
 	 *

tests/phpunit/tests/l10n/wpTextdomainRegistry.php

@@ -151,36 +151,46 @@ class Tests_L10n_wpTextdomainRegistry extends WP_UnitTestCase {
 
 	public function data_domains_locales() {
 		return array(
-			'Non-existent plugin'            => array(
+			'Non-existent plugin'                      => array(
 				'unknown-plugin',
 				'en_US',
 				false,
 			),
-			'Non-existent plugin with de_DE' => array(
+			'Non-existent plugin with de_DE'           => array(
 				'unknown-plugin',
 				'de_DE',
 				false,
 			),
-			'Available de_DE translations'   => array(
+			'Available de_DE translations'             => array(
 				'internationalized-plugin',
 				'de_DE',
 				WP_LANG_DIR . '/plugins/',
 			),
-			'Available es_ES translations'   => array(
+			'Available es_ES translations'             => array(
 				'internationalized-plugin',
 				'es_ES',
 				WP_LANG_DIR . '/plugins/',
 			),
-			'Unavailable fr_FR translations' => array(
+			'Unavailable fr_FR translations'           => array(
 				'internationalized-plugin',
 				'fr_FR',
 				false,
 			),
-			'Unavailable en_US translations' => array(
+			'Unavailable en_US translations'           => array(
 				'internationalized-plugin',
 				'en_US',
 				false,
 			),
+			'Available de_DE translations (.l10n.php)' => array(
+				'internationalized-plugin-2',
+				'de_DE',
+				WP_LANG_DIR . '/plugins/',
+			),
+			'Available es_ES translations (.l10n.php)' => array(
+				'internationalized-plugin-2',
+				'es_ES',
+				WP_LANG_DIR . '/plugins/',
+			),
 		);
 	}
 }