i18n: Account for load_*_textdomain() after JIT loading.

When `load_*_textdomain()` functions are called after WordPress has already attempted just-in-time loading of translations, nothing happens. 

This updates the related logic to retry translation loading when a custom path is set to ensure all translations are available.

Additionally, this also fixes cases where an `en_US.mo` file is provided with non-English strings to override the default language.

Follow up to [59157].

Props swissspidy, peterwilsoncc, desrosj, apermo, sergeybiryukov, wildworks, tigriweb, twvania, looswebstudio, stimul, audrasjb, finntown, bluantinoo, timwhitlock, albigdd.
See #62337.

git-svn-id: https://develop.svn.wordpress.org/trunk@59430 602fd350-edb4-49c9-b593-d223f7449a82

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

@@ -153,6 +153,16 @@ class WP_Textdomain_Registry {
 	 * @param string $path   Language directory path.
 	 */
 	public function set_custom_path( $domain, $path ) {
+		// If just-in-time loading was triggered before, reset the entry so it can be tried again.
+
+		if ( isset( $this->all[ $domain ] ) ) {
+			$this->all[ $domain ] = array_filter( $this->all[ $domain ] );
+		}
+
+		if ( empty( $this->current[ $domain ] ) ) {
+			unset( $this->current[ $domain ] );
+		}
+
 		$this->custom_paths[ $domain ] = rtrim( $path, '/' );
 	}
 
@@ -336,7 +346,7 @@ class WP_Textdomain_Registry {
 		 * If no path is found for the given locale and a custom path has been set
 		 * using load_plugin_textdomain/load_theme_textdomain, use that one.
 		 */
-		if ( 'en_US' !== $locale && isset( $this->custom_paths[ $domain ] ) ) {
+		if ( isset( $this->custom_paths[ $domain ] ) ) {
 			$fallback_location = rtrim( $this->custom_paths[ $domain ], '/' ) . '/';
 			$this->set( $domain, $locale, $fallback_location );
 			return $fallback_location;

src/wp-includes/l10n.php

@@ -985,6 +985,9 @@ function load_default_textdomain( $locale = null ) {
  * @since 4.6.0 The function now tries to load the .mo file from the languages directory first.
  * @since 6.7.0 Translations are no longer immediately loaded, but handed off to the just-in-time loading mechanism.
  *
+ * @global WP_Textdomain_Registry $wp_textdomain_registry WordPress Textdomain Registry.
+ * @global array<string, WP_Translations|NOOP_Translations> $l10n An array of all currently loaded text domains.
+ *
  * @param string       $domain          Unique identifier for retrieving translated strings
  * @param string|false $deprecated      Optional. Deprecated. Use the $plugin_rel_path parameter instead.
  *                                      Default false.
@@ -994,7 +997,8 @@ function load_default_textdomain( $locale = null ) {
  */
 function load_plugin_textdomain( $domain, $deprecated = false, $plugin_rel_path = false ) {
 	/** @var WP_Textdomain_Registry $wp_textdomain_registry */
-	global $wp_textdomain_registry;
+	/** @var array<string, WP_Translations|NOOP_Translations> $l10n */
+	global $wp_textdomain_registry, $l10n;
 
 	if ( ! is_string( $domain ) ) {
 		return false;
@@ -1011,6 +1015,11 @@ function load_plugin_textdomain( $domain, $deprecated = false, $plugin_rel_path
 
 	$wp_textdomain_registry->set_custom_path( $domain, $path );
 
+	// If just-in-time loading was triggered before, reset the entry so it can be tried again.
+	if ( isset( $l10n[ $domain ] ) && $l10n[ $domain ] instanceof NOOP_Translations ) {
+		unset( $l10n[ $domain ] );
+	}
+
 	return true;
 }
 
@@ -1022,6 +1031,7 @@ function load_plugin_textdomain( $domain, $deprecated = false, $plugin_rel_path
  * @since 6.7.0 Translations are no longer immediately loaded, but handed off to the just-in-time loading mechanism.
  *
  * @global WP_Textdomain_Registry $wp_textdomain_registry WordPress Textdomain Registry.
+ * @global array<string, WP_Translations|NOOP_Translations> $l10n An array of all currently loaded text domains.
  *
  * @param string $domain             Text domain. Unique identifier for retrieving translated strings.
  * @param string $mu_plugin_rel_path Optional. Relative to `WPMU_PLUGIN_DIR` directory in which the .mo
@@ -1030,7 +1040,8 @@ function load_plugin_textdomain( $domain, $deprecated = false, $plugin_rel_path
  */
 function load_muplugin_textdomain( $domain, $mu_plugin_rel_path = '' ) {
 	/** @var WP_Textdomain_Registry $wp_textdomain_registry */
-	global $wp_textdomain_registry;
+	/** @var array<string, WP_Translations|NOOP_Translations> $l10n */
+	global $wp_textdomain_registry, $l10n;
 
 	if ( ! is_string( $domain ) ) {
 		return false;
@@ -1040,6 +1051,11 @@ function load_muplugin_textdomain( $domain, $mu_plugin_rel_path = '' ) {
 
 	$wp_textdomain_registry->set_custom_path( $domain, $path );
 
+	// If just-in-time loading was triggered before, reset the entry so it can be tried again.
+	if ( isset( $l10n[ $domain ] ) && $l10n[ $domain ] instanceof NOOP_Translations ) {
+		unset( $l10n[ $domain ] );
+	}
+
 	return true;
 }
 
@@ -1056,6 +1072,7 @@ function load_muplugin_textdomain( $domain, $mu_plugin_rel_path = '' ) {
  * @since 6.7.0 Translations are no longer immediately loaded, but handed off to the just-in-time loading mechanism.
  *
  * @global WP_Textdomain_Registry $wp_textdomain_registry WordPress Textdomain Registry.
+ * @global array<string, WP_Translations|NOOP_Translations> $l10n An array of all currently loaded text domains.
  *
  * @param string       $domain Text domain. Unique identifier for retrieving translated strings.
  * @param string|false $path   Optional. Path to the directory containing the .mo file.
@@ -1064,7 +1081,8 @@ function load_muplugin_textdomain( $domain, $mu_plugin_rel_path = '' ) {
  */
 function load_theme_textdomain( $domain, $path = false ) {
 	/** @var WP_Textdomain_Registry $wp_textdomain_registry */
-	global $wp_textdomain_registry;
+	/** @var array<string, WP_Translations|NOOP_Translations> $l10n */
+	global $wp_textdomain_registry, $l10n;
 
 	if ( ! is_string( $domain ) ) {
 		return false;
@@ -1076,6 +1094,11 @@ function load_theme_textdomain( $domain, $path = false ) {
 
 	$wp_textdomain_registry->set_custom_path( $domain, $path );
 
+	// If just-in-time loading was triggered before, reset the entry so it can be tried again.
+	if ( isset( $l10n[ $domain ] ) && $l10n[ $domain ] instanceof NOOP_Translations ) {
+		unset( $l10n[ $domain ] );
+	}
+
 	return true;
 }
 

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

@@ -7,7 +7,11 @@ Version: 1.0.0
 Text Domain: custom-internationalized-plugin
 */
 
-load_plugin_textdomain( 'custom-internationalized-plugin', false, dirname( plugin_basename( __FILE__ ) ) . '/languages' );
+function custom_i18n_load_textdomain() {
+	load_plugin_textdomain( 'custom-internationalized-plugin', false, dirname( plugin_basename( __FILE__ ) ) . '/languages' );
+}
+
+add_action( 'init', 'custom_i18n_load_textdomain' );
 
 function custom_i18n_plugin_test() {
 	return __( 'This is a dummy plugin', 'custom-internationalized-plugin' );

tests/phpunit/tests/l10n/loadTextdomainJustInTime.php

@@ -342,4 +342,34 @@ class Tests_L10n_LoadTextdomainJustInTime extends WP_UnitTestCase {
 		$this->assertFalse( is_textdomain_loaded( $textdomain ) );
 		$this->assertSame( 1, $filter->get_call_count() );
 	}
+
+	/**
+	 * @ticket 44937
+	 * @ticket 62337
+	 *
+	 * @covers ::load_plugin_textdomain
+	 * @covers ::is_textdomain_loaded
+	 * @covers WP_Textdomain_Registry::set_custom_path
+	 */
+	public function test_plugin_translation_should_be_translated_when_calling_load_plugin_textdomain_too_late() {
+		require_once DIR_TESTDATA . '/plugins/custom-internationalized-plugin/custom-internationalized-plugin.php';
+
+		add_filter( 'locale', array( $this, 'filter_set_locale_to_german' ) );
+
+		$is_textdomain_loaded_before = is_textdomain_loaded( 'custom-internationalized-plugin' );
+		$output_before               = custom_i18n_plugin_test();
+
+		$is_textdomain_loaded_middle = is_textdomain_loaded( 'custom-internationalized-plugin' );
+
+		custom_i18n_load_textdomain();
+
+		$output_after               = custom_i18n_plugin_test();
+		$is_textdomain_loaded_after = is_textdomain_loaded( 'custom-internationalized-plugin' );
+
+		$this->assertFalse( $is_textdomain_loaded_before );
+		$this->assertFalse( $is_textdomain_loaded_middle );
+		$this->assertSame( 'This is a dummy plugin', $output_before );
+		$this->assertSame( 'Das ist ein Dummy Plugin', $output_after );
+		$this->assertTrue( $is_textdomain_loaded_after );
+	}
 }

tests/phpunit/tests/l10n/wpLocaleSwitcher.php

@@ -493,6 +493,8 @@ class Tests_L10n_wpLocaleSwitcher extends WP_UnitTestCase {
 
 		require_once DIR_TESTDATA . '/plugins/custom-internationalized-plugin/custom-internationalized-plugin.php';
 
+		custom_i18n_load_textdomain();
+
 		$actual = custom_i18n_plugin_test();
 
 		switch_to_locale( 'es_ES' );

tests/phpunit/tests/l10n/wpTextdomainRegistry.php

@@ -39,9 +39,10 @@ class Tests_L10n_wpTextdomainRegistry extends WP_UnitTestCase {
 			$this->instance->has( 'foo' ),
 			'Incorrect availability status for textdomain with custom path'
 		);
-		$this->assertFalse(
+		$this->assertSame(
+			WP_LANG_DIR . '/bar/',
 			$this->instance->get( 'foo', 'en_US' ),
-			'Should not return custom path for textdomain and en_US locale'
+			'Should return custom path for textdomain and en_US locale'
 		);
 		$this->assertSame(
 			WP_LANG_DIR . '/bar/',