Ticket #28197: fallback-languages-2.diff

wp-includes/l10n.php

@@ -454 +454 @@
          */
         $mofile = apply_filters( 'load_textdomain_mofile', $mofile, $domain );
 
-        if ( !is_readable( $mofile ) ) return false;
+        if ( !is_readable( $mofile ) ) {
+                $mofile = get_fallback_translation( $mofile, $domain );
+                if ( false === $mofile ) {
+                        return false;
+                }
+        }
 
         $mo = new MO();
         if ( !$mo->import_from_file( $mofile ) ) return false;
@@ -468 +473 @@
 }
 
 /**
+ * Looks for a fallback translation file to use if locale is not available.
+ *
+ * @since 4.0.0
+ *
+ * @param string $domain Text domain. Unique identifier for retrieving translated strings.
+ * @param string $mofile Path to the .mo file.
+ * @return false or string $mofile Path
+ */
+function get_fallback_translation( $mofile, $domain ) {
+
+        $fallback = strtok( get_locale(), '_' );
+
+        $fallback_mofile = dirname( $mofile ) . '/' . $domain . '-' . $fallback . '.mo';
+
+        $mofile = apply_filters( 'load_textdomain_mofile', $fallback_mofile, $domain );
+        if ( is_readable( $mofile ) ) {
+                return $mofile;
+        }
+        return false;
+}
+
+/**
  * Unload translations for a text domain.
  *
  * @since 3.0.0