Ticket #15677: 15677.12.patch

src/wp-admin/includes/translation-install.php

@@ +1 @@
+<?php
+/**
+ * WordPress Translation Install Administration API
+ *
+ * @package WordPress
+ * @subpackage Administration
+ */
+
+
+/**
+ * Retrieve translations from WordPress Translation API.
+ *
+ * @since 4.0.0
+ *
+ * @param string       $type Type of translations. Accepts 'plugins', 'themes', 'core'.
+ * @param array|object $args Translation API arguments. Optional.
+ * @return object|WP_Error On success an object of translations, WP_Error on failure.
+ */
+function translations_api( $type, $args = null ) {
+        include( ABSPATH . WPINC . '/version.php' ); // include an unmodified $wp_version
+
+        if ( ! in_array( $type, array( 'plugins', 'themes', 'core' ) ) ) {
+                return  new WP_Error( 'invalid_type', __( 'Invalid translation type.' ) );
+        }
+
+        /**
+         * Allows a plugin to override the WordPress.org Translation Install API entirely.
+         *
+         * @since 4.0.0
+         *
+         * @param bool|array  $result The result object. Default false.
+         * @param string      $type   The type of translations being requested.
+         * @param object      $args   Translation API arguments.
+         */
+        $res = apply_filters( 'translations_api', false, $type, $args );
+
+        if ( false === $res ) {
+                $url = $http_url = 'http://api.wordpress.org/translations/' . $type . '/1.0/';
+                if ( $ssl = wp_http_supports( array( 'ssl' ) ) ) {
+                        $url = set_url_scheme( $url, 'https' );
+                }
+
+                $options = array(
+                        'timeout' => 3,
+                        'body' => array(
+                                'wp_version' => $wp_version,
+                                'locale'     => get_locale(),
+                                'version'    => $args['version'], // Version of plugin, theme or core
+                        ),
+                );
+
+                if ( 'core' !== $type ) {
+                        $options['body']['slug'] = $args['slug']; // Plugin or theme slug
+                }
+
+                $request = wp_remote_post( $url, $options );
+
+                if ( $ssl && is_wp_error( $request ) ) {
+                        trigger_error( __( 'An unexpected error occurred. Something may be wrong with WordPress.org or this server&#8217;s configuration. If you continue to have problems, please try the <a href="https://wordpress.org/support/">support forums</a>.' ) . ' ' . __( '(WordPress could not establish a secure connection to WordPress.org. Please contact your server administrator.)' ), headers_sent() || WP_DEBUG ? E_USER_WARNING : E_USER_NOTICE );
+
+                        $request = wp_remote_post( $http_url, $options );
+                }
+
+                if ( is_wp_error( $request ) ) {
+                        $res = new WP_Error( 'translations_api_failed', __( 'An unexpected error occurred. Something may be wrong with WordPress.org or this server&#8217;s configuration. If you continue to have problems, please try the <a href="https://wordpress.org/support/">support forums</a>.' ), $request->get_error_message() );
+                } else {
+                        $res = json_decode( wp_remote_retrieve_body( $request ), true );
+                        if ( ! is_object( $res ) && ! is_array( $res ) ) {
+                                $res = new WP_Error( 'translations_api_failed', __( 'An unexpected error occurred. Something may be wrong with WordPress.org or this server&#8217;s configuration. If you continue to have problems, please try the <a href="https://wordpress.org/support/">support forums</a>.' ), wp_remote_retrieve_body( $request ) );
+                        }
+                }
+        }
+
+        /**
+         * Filter the Translation Install API response results.
+         *
+         * @since 4.0.0
+         *
+         * @param object|WP_Error $res  Response object or WP_Error.
+         * @param string          $type The type of translations being requested.
+         * @param object          $args Translation API arguments.
+         */
+        return apply_filters( 'translations_api_result', $res, $type, $args );
+}
+
+/**
+ * Get available translations from the WordPress.org API.
+ *
+ * @since 4.0.0
+ *
+ * @see translations_api()
+ *
+ * @return array Array of translations, each an array of data. If the API response results
+ *               in an error, an empty array will be returned.
+ */
+function wp_get_available_translations() {
+        if ( ! defined( 'WP_INSTALLING' ) && false !== ( $translations = get_site_transient( 'available_translations' ) ) ) {
+                return $translations;
+        }
+
+        include( ABSPATH . WPINC . '/version.php' ); // include an unmodified $wp_version
+
+        $api = translations_api( 'core', array( 'version' => $wp_version ) );
+
+        if ( is_wp_error( $api ) || empty( $api['translations'] ) ) {
+                return array();
+        }
+
+        $translations = array();
+        // Key the array with the language code for now
+        foreach ( $api['translations'] as $translation ) {
+                $translations[ $translation['language'] ] = $translation;
+        }
+
+        if ( ! defined( 'WP_INSTALLING' ) ) {
+                set_site_transient( 'available_translations', $translations, 3 * HOUR_IN_SECONDS );
+        }
+
+        return $translations;
+}
+
+/**
+ * Output the select form for the language selection on the installation screen.
+ *
+ * @since 4.0.0
+ *
+ * @param array $languages Array of available languages (populated via the Translation API).
+ */
+function wp_install_language_form( $languages ) {
+        $installed_languages = get_available_languages();
+
+        echo "<label class='screen-reader-text' for='language'>Select a default language</label>\n";
+        echo "<select size='14' name='language' id='language'>\n";
+        echo '<option value="" lang="en" selected="selected" data-continue="Continue" data-installed="1">English (United States)</option>';
+        echo "\n";
+
+        if ( defined( 'WPLANG' ) && ( '' !== WPLANG ) && ( 'en_US' !== WPLANG ) ) {
+                if ( isset( $languages[ WPLANG ] ) ) {
+                        $language = $languages[ WPLANG ];
+                        echo '<option value="' . esc_attr( $language['language'] ) . '" lang="' . esc_attr( $language['iso'][1] ) . '">' . esc_html( $language['native_name'] ) . "</option>\n";
+                        unset( $languages[ WPLANG ] );
+                }
+        }
+
+        foreach ( $languages as $language ) {
+                printf( '<option value="%s" lang="%s" data-continue="%s"%s>%s</option>' . "\n",
+                        esc_attr( $language['language'] ),
+                        esc_attr( $language['iso'][1] ),
+                        esc_attr( $language['strings']['continue'] ),
+                        in_array( $language['language'], $installed_languages ) ? ' data-installed="1"' : '',
+                        esc_html( $language['native_name'] ) );
+        }
+        echo "</select>\n";
+        echo '<p class="step"><span class="spinner"></span><input id="language-continue" type="submit" class="button button-primary button-large" value="Continue" /></p>';
+}
+
+/**
+ * Download a language pack.
+ *
+ * @since 4.0.0
+ *
+ * @see wp_get_available_translations()
+ *
+ * @param string $download Language code to download.
+ * @return string|bool Returns the language code if successfully downloaded
+ *                     (or already installed), or false on failure.
+ */
+function wp_download_language_pack( $download ) {
+        // Check if the translation is already installed.
+        if ( in_array( $download, get_available_languages() ) ) {
+                return $download;
+        }
+
+        if ( defined( 'DISALLOW_FILE_MODS' ) && DISALLOW_FILE_MODS ) {
+                return false;
+        }
+
+        // Confirm the translation is one we can download.
+        $translations = wp_get_available_translations();
+        if ( ! $translations ) {
+                return false;
+        }
+        foreach ( $translations as $translation ) {
+                if ( $translation['language'] === $download ) {
+                        $translation_to_load = true;
+                        break;
+                }
+        }
+
+        if ( empty( $translation_to_load ) ) {
+                return false;
+        }
+        $translation = (object) $translation;
+
+        require_once ABSPATH . 'wp-admin/includes/class-wp-upgrader.php';
+        $skin = new Automatic_Upgrader_Skin;
+        $upgrader = new Language_Pack_Upgrader( $skin );
+        $translation->type = 'core';
+        /**
+         * @todo failures (such as non-direct FS)
+         */
+        $result = $upgrader->upgrade( $translation, array( 'clear_update_cache' => false ) );
+        return $translation->language;
+}

src/wp-admin/includes/upgrade.php

@@ -1419 +1419 @@
  */
 function maybe_create_table($table_name, $create_ddl) {
         global $wpdb;
-        
+
         $query = $wpdb->prepare( "SHOW TABLES LIKE %s", $wpdb->esc_like( $table_name ) );
 
         if ( $wpdb->get_var( $query ) == $table_name ) {
@@ -2192 +2192 @@
         dbDelta( $ms_queries );
 }
 endif;
-
-/**
- * Output the input fields for the language selection form on the installation screen.
- *
- * @since 4.0.0
- *
- * @see wp_get_available_translations_from_api()
- * 
- * @param array $languages Array of available languages (populated via the Translations API).
- */
-function wp_install_language_form( $languages ) {
-        $installed_languages = get_available_languages();
-
-        echo "<label class='screen-reader-text' for='language'>Select a default language</label>\n";
-        echo "<select size='14' name='language' id='language'>\n";
-        echo '<option value="" lang="en" selected="selected" data-continue="Continue" data-installed="1">English (United States)</option>';
-        echo "\n";
-
-        if ( defined( 'WPLANG' ) && ( '' !== WPLANG ) && ( 'en_US' !== WPLANG ) ) {
-                if ( isset( $languages[ WPLANG ] ) ) {
-                        $language = $languages[ WPLANG ];
-                        echo '<option value="' . esc_attr( $language['language'] ) . '" lang="' . esc_attr( $language['iso'][1] ) . '">' . esc_html( $language['native_name'] ) . "</option>\n";
-                }
-        }
-
-        foreach ( $languages as $language ) {
-                printf( '<option value="%s" lang="%s" data-continue="%s"%s>%s</option>' . "\n",
-                        esc_attr( $language['language'] ),
-                        esc_attr( $language['iso'][1] ),
-                        esc_attr( $language['strings']['continue'] ),
-                        in_array( $language['language'], $installed_languages ) ? ' data-installed="1"' : '',
-                        esc_html( $language['native_name'] ) );
-        }
-        echo "</select>\n";
-        echo '<p class="step"><span class="spinner"></span><input id="language-continue" type="submit" class="button button-primary button-large" value="Continue" /></p>';
-}
-
-/**
- * Get available translations from the WordPress.org API.
- *
- * @since 4.0.0
- *
- * @see wp_remote_post()
- *
- * @return array Array of translations, each an array of data.
- */
-function wp_get_available_translations_from_api() {
-        $url = 'http://api.wordpress.org/translations/core/1.0/';
-        if ( wp_http_supports( array( 'ssl' ) ) ) {
-                $url = set_url_scheme( $url, 'https' );
-        }
-
-        $options = array(
-                'timeout' => 3,
-                'body' => array( 'version' => $GLOBALS['wp_version'] ),
-        );
-
-        $response = wp_remote_post( $url, $options );
-        $body = wp_remote_retrieve_body( $response );
-        if ( $body && $body = json_decode( $body, true ) ) {
-                $translations = array();
-                // Key the array with the language code for now
-                foreach ( $body['translations'] as $translation ) {
-                        $translations[ $translation['language'] ] = $translation;
-                }
-                return $translations;
-        }
-        return false;
-}
-
-/**
- * Download a language pack.
- *
- * @since 4.0.0
- *
- * @see wp_get_available_translations_from_api()
- *
- * @param string $download Language code to download.
- * @return string|bool Returns the language code if successfully downloaded
- *                     (or already installed), or false on failure.
- */
-function wp_install_download_language_pack( $download ) {
-        // Check if the translation is already installed.
-        if ( in_array( $download, get_available_languages() ) ) {
-                return $download;
-        }
-
-        // Confirm the translation is one we can download.
-        $translations = wp_get_available_translations_from_api();
-        if ( ! $translations ) {
-                return false;
-        }
-        foreach ( $translations as $translation ) {
-                if ( $translation['language'] === $download ) {
-                        $translation_to_load = true;
-                        break;
-                }
-        }
-
-        if ( empty( $translation_to_load ) ) {
-                return false;
-        }
-        $translation = (object) $translation;
-
-        require_once ABSPATH . 'wp-admin/includes/class-wp-upgrader.php';
-        $skin = new Automatic_Upgrader_Skin;
-        $upgrader = new Language_Pack_Upgrader( $skin );
-        $translation->type = 'core';
-        /**
-         * @todo failures (such as non-direct FS)
-         */
-        $upgrader->upgrade( $translation, array( 'clear_update_cache' => false ) );
-        return $translation->language;
-}
-
-/**
- * Load a translation during the install process.
- *
- * @since 4.0.0
- *
- * @see load_textdomain()
- *
- * @param string $translation Translation to load.
- * @return string|bool Returns the language code if successfully loaded,
- *                     or false on failure.
- */
-function wp_install_load_language( $translation ) {
-        if ( ! empty( $translation ) ) {
-                if ( in_array( $translation, get_available_languages() ) ) {
-                        $translation_to_load = $translation;
-                }
-        }
-
-        if ( empty( $translation_to_load ) ) {
-                return false;
-        }
-
-        unload_textdomain( 'default' ); // Start over.
-        load_textdomain( 'default', WP_LANG_DIR . "/{$translation_to_load}.mo" );
-        load_textdomain( 'default', WP_LANG_DIR . "/admin-{$translation_to_load}.mo" );
-        return $translation_to_load;
-}

src/wp-admin/install.php

@@ -38 +38 @@
 /** Load WordPress Administration Upgrade API */
 require_once( ABSPATH . 'wp-admin/includes/upgrade.php' );
 
+/** Load WordPress Translation Install API */
+require_once( ABSPATH . 'wp-admin/includes/translation-install.php' );
+
 /** Load wpdb */
 require_once( ABSPATH . WPINC . '/wp-db.php' );
 
@@ -181 +184 @@
 switch($step) {
         case 0: // Step 0
 
-                if ( empty( $_GET['language'] ) && ( $languages = wp_get_available_translations_from_api() ) ) {
+                if ( empty( $_GET['language'] ) && ( $languages = wp_get_available_translations() ) ) {
                         display_header( 'language-chooser' );
                         echo '<form id="setup" method="post" action="?step=1">';
                         wp_install_language_form( $languages );
@@ -193 +196 @@
 
         case 1: // Step 1, direct link or from language chooser.
                 if ( ! empty( $_REQUEST['language'] ) ) {
-                        $loaded_language = wp_install_download_language_pack( $_REQUEST['language'] );
+                        $loaded_language = wp_download_language_pack( $_REQUEST['language'] );
                         if ( $loaded_language ) {
-                                wp_install_load_language( $loaded_language );
+                                wp_switch_default_textdomain( $loaded_language );
                         }
                 }
 
@@ -212 +215 @@
                 break;
         case 2:
                 if ( !empty( $_REQUEST['language'] ) ) {
-                        $loaded_language = wp_install_load_language( $_REQUEST['language'] );
+                        $loaded_language = wp_switch_default_textdomain( $_REQUEST['language'] );
                 } else {
                         $loaded_language = 'en_US';
                 }

src/wp-admin/network/settings.php

@@ -102 +102 @@
                                         <input name="admin_email" type="email" id="admin_email" class="regular-text" value="<?php echo esc_attr( get_site_option( 'admin_email' ) ) ?>" />
                                         <p class="description">
                                                 <?php _e( 'This email address will receive notifications. Registration and support emails will also come from this address.' ); ?>
-                                        </p>    
+                                        </p>
                                 </td>
                         </tr>
                 </table>
@@ -165 +165 @@
 <?php echo esc_textarea( $limited_email_domains == '' ? '' : implode( "\n", (array) $limited_email_domains ) ); ?></textarea>
                                         <p class="description">
                                                 <?php _e( 'If you want to limit site registrations to certain domains. One domain per line.' ) ?>
-                                        </p>    
+                                        </p>
                                 </td>
                         </tr>
 
@@ -231 +231 @@
 <?php echo esc_textarea( get_site_option( 'first_comment' ) ) ?></textarea>
                                         <p class="description">
                                                 <?php _e( 'The first comment on a new site.' ) ?>
-                                        </p>    
+                                        </p>
                                 </td>
                         </tr>
                         <tr>
@@ -273 +273 @@
                         </tr>
                 </table>
 
-<?php
+                <?php
                 $languages = get_available_languages();
                 if ( ! empty( $languages ) ) {
-                        $lang = get_site_option( 'WPLANG' );
-?>
-                <h3><?php _e( 'Language Settings' ); ?></h3>
-                <table class="form-table">
+                        ?>
+                        <h3><?php _e( 'Language Settings' ); ?></h3>
+                        <table class="form-table">
                                 <tr>
                                         <th><label for="WPLANG"><?php _e( 'Default Language' ); ?></label></th>
                                         <td>
-                                                <select name="WPLANG" id="WPLANG">
-                                                        <?php mu_dropdown_languages( $languages, get_site_option( 'WPLANG' ) ); ?>
-                                                </select>
+                                                <?php
+                                                $lang = get_site_option( 'WPLANG' );
+                                                if ( ! in_array( $lang, $languages ) ) {
+                                                        $lang = '';
+                                                }
+
+                                                wp_dropdown_languages( array(
+                                                        'name'      => 'WPLANG',
+                                                        'id'        => 'WPLANG',
+                                                        'selected'  => $lang,
+                                                        'languages' => $languages,
+                                                ) );
+                                                ?>
                                         </td>
                                 </tr>
-                </table>
-<?php
-                } // languages
-?>
+                        </table>
+                        <?php
+                }
+                ?>
 
                 <h3><?php _e( 'Menu Settings' ); ?></h3>
                 <table id="menu" class="form-table">
@@ -324 +333 @@
                         </tr>
                 </table>
 
-                <?php 
+                <?php
                 /**
                  * Fires at the end of the Network Settings form, before the submit button.
                  *

src/wp-admin/options-general.php

@@ -302 +302 @@
 </select></td>
 </tr>
 <?php do_settings_fields('general', 'default'); ?>
+
 <?php
-        $languages = get_available_languages();
-        if ( $languages ) :
-?>
+$languages = get_available_languages();
+if ( ! empty( $languages ) ) {
+        ?>
         <tr>
-                <th width="33%" scope="row"><label for="WPLANG"><?php _e('Site Language') ?></label></th>
+                <th width="33%" scope="row"><label for="WPLANG"><?php _e( 'Site Language' ); ?></label></th>
                 <td>
-                        <?php wp_dropdown_languages( array(
+                        <?php
+                        $locale = get_locale();
+                        // Check if current locale is still installed. en_US will fail this test, but that's okay.
+                        if ( ! in_array( $locale, $languages ) ) {
+                                $locale = '';
+                        }
+
+                        wp_dropdown_languages( array(
                                 'name'      => 'WPLANG',
                                 'id'        => 'WPLANG',
-                                'selected'  => get_option( 'WPLANG' ),
+                                'selected'  => $locale,
                                 'languages' => $languages,
-                        ) ); ?>
+                        ) );
+
+                        // Add note about deprecated WPLANG constant.
+                        if ( defined( 'WPLANG' ) && ( '' !== WPLANG ) && $locale !== WPLANG && is_super_admin() ) {
+                                ?>
+                                <p class="description">
+                                        <?php _e( '<strong>Note:</strong> The <code>WPLANG</code> constant in your <code>wp-config.php</code> file is deprecated.' ); ?>
+                                </p>
+                                <?php
+                        }
+                        ?>
                 </td>
         </tr>
-<?php
-        endif;
+        <?php
+}
 ?>
 </table>
 

src/wp-admin/options.php

@@ -151 +151 @@
                 $options = $whitelist_options[ $option_page ];
         }
 
-        // Handle custom date/time formats
+        // Handle custom date/time formats.
         if ( 'general' == $option_page ) {
                 if ( !empty($_POST['date_format']) && isset($_POST['date_format_custom']) && '\c\u\s\t\o\m' == wp_unslash( $_POST['date_format'] ) )
                         $_POST['date_format'] = $_POST['date_format_custom'];
@@ -180 +180 @@
                         }
                         update_option( $option, $value );
                 }
+
+                // Switch translation in case WPLANG was changed.
+                $language = wp_unslash( trim( $_POST[ 'WPLANG' ] ) );
+                if ( $language ) {
+                        wp_switch_default_textdomain( $language );
+                } else {
+                        unload_textdomain( 'default' );
+                }
         }
 
         /**

src/wp-admin/setup-config.php

@@ -32 +32 @@
 
 require( ABSPATH . 'wp-settings.php' );
 
-require( ABSPATH . 'wp-admin/includes/upgrade.php' );
+/** Load WordPress Administration Upgrade API */
+require_once( ABSPATH . 'wp-admin/includes/upgrade.php' );
 
+/** Load WordPress Translation Install API */
+require_once( ABSPATH . 'wp-admin/includes/translation-install.php' );
+
 nocache_headers();
 
 // Support wp-config-sample.php one level up, for the develop repo.
@@ -88 +92 @@
 switch($step) {
         case -1:
 
-                if ( empty( $_GET['language'] ) && ( $languages = wp_get_available_translations_from_api() ) ) {
+                if ( empty( $_GET['language'] ) && ( $languages = wp_get_available_translations() ) ) {
                         setup_config_display_header( 'language-chooser' );
                         echo '<form id="setup" method="post" action="?step=0">';
                         wp_install_language_form( $languages );
@@ -100 +104 @@
 
         case 0:
                 if ( ! empty( $_REQUEST['language'] ) ) {
-                        $loaded_language = wp_install_download_language_pack( $_REQUEST['language'] );
+                        $loaded_language = wp_download_language_pack( $_REQUEST['language'] );
                         if ( $loaded_language ) {
-                                wp_install_load_language( $loaded_language );
+                                wp_switch_default_textdomain( $loaded_language );
                         }
                 }
 
@@ -136 +140 @@
         break;
 
         case 1:
-                $loaded_language = wp_install_load_language( $_REQUEST['language'] );
+                $loaded_language = wp_switch_default_textdomain( $_REQUEST['language'] );
                 setup_config_display_header();
         ?>
 <form method="post" action="setup-config.php?step=2">
@@ -176 +180 @@
         break;
 
         case 2:
-        $loaded_language = wp_install_load_language( $_REQUEST['language'] );
+        $loaded_language = wp_switch_default_textdomain( $_REQUEST['language'] );
         $dbname = trim( wp_unslash( $_POST[ 'dbname' ] ) );
         $uname = trim( wp_unslash( $_POST[ 'uname' ] ) );
         $pwd = trim( wp_unslash( $_POST[ 'pwd' ] ) );

src/wp-includes/l10n.php

@@ -24 +24 @@
  * @return string The locale of the blog or from the 'locale' hook.
  */
 function get_locale() {
-        global $locale;
+        global $locale, $wp_local_package;
 
         if ( isset( $locale ) ) {
                 /**
@@ -38 +38 @@
         }
 
         // WPLANG is defined in wp-config.
-        if ( defined( 'WPLANG' ) )
+        if ( defined( 'WPLANG' ) ) {
                 $locale = WPLANG;
+        }
 
+        if ( isset( $wp_local_package ) ) {
+                $locale = $wp_local_package;
+        }
+
         // If multisite, check options.
         if ( is_multisite() ) {
                 // Don't check blog option when installing.
-                if ( defined( 'WP_INSTALLING' ) || ( false === $ms_locale = get_option( 'WPLANG' ) ) )
-                        $ms_locale = get_site_option('WPLANG');
+                if ( defined( 'WP_INSTALLING' ) || ( false === $ms_locale = get_option( 'WPLANG' ) ) ) {
+                        $ms_locale = get_site_option( 'WPLANG' );
+                }
 
-                if ( $ms_locale !== false )
+                if ( $ms_locale !== false ) {
                         $locale = $ms_locale;
-        } elseif ( ! defined( 'WP_INSTALLING' ) ) {
+                }
+        } else {
                 $db_locale = get_option( 'WPLANG' );
-                if ( $db_locale ) {
+                if ( $db_locale !== false ) {
                         $locale = $db_locale;
                 }
         }
 
-        if ( empty( $locale ) )
+        if ( empty( $locale ) ) {
                 $locale = 'en_US';
+        }
 
         /** This filter is documented in wp-includes/l10n.php */
         return apply_filters( 'locale', $locale );
@@ -523 +531 @@
  * @see load_textdomain()
  *
  * @since 1.5.0
+ *
+ * @param string $locale Optional. Locale to load. Defaults to get_locale().
  */
-function load_default_textdomain() {
-        $locale = get_locale();
+function load_default_textdomain( $locale = null ) {
+        if ( null === $locale ) {
+                $locale = get_locale();
+        }
 
-        load_textdomain( 'default', WP_LANG_DIR . "/$locale.mo" );
+        $return = load_textdomain( 'default', WP_LANG_DIR . "/$locale.mo" );
 
         if ( ( is_multisite() || ( defined( 'WP_INSTALLING_NETWORK' ) && WP_INSTALLING_NETWORK ) ) && ! file_exists(  WP_LANG_DIR . "/admin-$locale.mo" ) ) {
                 load_textdomain( 'default', WP_LANG_DIR . "/ms-$locale.mo" );
-                return;
+                return $return;
         }
 
         if ( is_admin() || ( defined( 'WP_REPAIRING' ) && WP_REPAIRING ) )
@@ -540 +552 @@
         if ( is_network_admin() || ( defined( 'WP_INSTALLING_NETWORK' ) && WP_INSTALLING_NETWORK ) )
                 load_textdomain( 'default', WP_LANG_DIR . "/admin-network-$locale.mo" );
 
+        return $return;
 }
 
 /**
@@ -818 +831 @@
 }
 
 /**
- * Language selector. More to come.
+ * Language selector.
  *
  * @since 4.0.0
  *
  * @see get_available_languages()
+ * @see wp_get_available_translations()
  *
  * @param array $args Optional arguments. Default empty array.
  */
 function wp_dropdown_languages( $args = array() ) {
-        if ( isset( $args['languages'] ) ) {
-                $languages = $args['languages'];
-        } else {
-                $languages = get_available_languages();
+        require_once( ABSPATH . 'wp-admin/includes/translation-install.php' );
+
+        $args = wp_parse_args( $args, array(
+                'id'        => '',
+                'name'      => '',
+                'languages' => array(),
+                'selected'  => ''
+        ) );
+
+        if ( empty( $args['languages'] ) ) {
+                return false;
         }
 
+        $translations = wp_get_available_translations();
+
+        /*
+         * $args['languages'] should only contain the locales. Find the locale in
+         * $translations to get the native name. Falls back to locale.
+         */
+        $languages = array();
+        foreach ( $args['languages'] as $locale ) {
+                if ( isset( $translations[ $locale ] ) ) {
+                        $translation = $translations[ $locale ];
+                        $languages[] = $translation;
+                } else {
+                        $languages[] = array(
+                                'language'    => $locale,
+                                'native_name' => $locale,
+                                'lang'        => '',
+                        );
+                }
+        }
+
         printf( '<select name="%s" id="%s">', esc_attr( $args['name'] ), esc_attr( $args['id'] ) );
-        echo '<option value="">en_US</option>';
+
+        // List installed languages.
+        echo '<option value="">English (United States)</option>';
         foreach ( $languages as $language ) {
-                $selected = selected( $language, $args['selected'], false );
-                echo '<option value="' . esc_attr( $language ) .'"' . $selected . '>' . $language . '</option>';
+                $selected = selected( $language['language'], $args['selected'], false );
+                printf(
+                        '<option value="%s" lang="%s"%s>%s</option>',
+                        esc_attr( $language['language'] ),
+                        esc_attr( $language['iso'][1] ),
+                        $selected,
+                        esc_html( $language['native_name'] )
+                );
         }
+
         echo '</select>';
 }
+
+/**
+ * Switch translation for default translation.
+ *
+ * @since 4.0.0
+ *
+ * @see load_default_textdomain()
+ *
+ * @param string $translation Translation to load.
+ *  string|bool Returns the language code if successfully loaded,
+ *              or false on failure.
+ */
+function wp_switch_default_textdomain( $translation ) {
+        if ( ! empty( $translation ) ) {
+                if ( in_array( $translation, get_available_languages() ) ) {
+                        $translation_to_load = $translation;
+                }
+        }
+
+
+        if ( empty( $translation_to_load ) ) {
+                return false;
+        }
+
+        if ( $translation_to_load === get_locale() ) {
+                return false;
+        }
+
+        unload_textdomain( 'default' ); // Start over.
+        $result = load_default_textdomain( $translation_to_load );
+
+        if ( ! $result ) {
+                return false;
+        }
+
+        return $translation_to_load;
+}

wp-config-sample.php

@@ -62 +62 @@
 $table_prefix  = 'wp_';
 
 /**
- * WordPress Localized Language, defaults to English.
- *
- * Change this to localize WordPress. A corresponding MO file for the chosen
- * language must be installed to wp-content/languages. For example, install
- * de_DE.mo to wp-content/languages and set WPLANG to 'de_DE' to enable German
- * language support.
- */
-define('WPLANG', '');
-
-/**
  * For developers: WordPress debugging mode.
  *
  * Change this to true to enable the display of notices during development.