Index: includes/locale.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/locale.inc,v
retrieving revision 1.207
diff -u -r1.207 locale.inc
--- includes/locale.inc	19 Mar 2009 10:48:51 -0000	1.207
+++ includes/locale.inc	21 Mar 2009 00:00:02 -0000
@@ -2379,6 +2379,7 @@
   }
 
   // Construct the JavaScript file, if there are translations.
+  $data_hash = NULL;
   $data = $status = '';
   if (!empty($translations)) {
 
@@ -2397,22 +2398,23 @@
   $dir = file_create_path(variable_get('locale_js_directory', 'languages'));
 
   // Delete old file, if we have no translations anymore, or a different file to be saved.
-  if (!empty($language->javascript) && (!$data || $language->javascript != $data_hash)) {
+  $changed_hash = $language->javascript != $data_hash;
+  if (!empty($language->javascript) && (!$data || $changed_hash)) {
     file_unmanaged_delete(file_create_path($dir . '/' . $language->language . '_' . $language->javascript . '.js'));
     $language->javascript = '';
     $status = 'deleted';
   }
 
-  // Only create a new file if the content has changed.
-  if ($data && $language->javascript != $data_hash) {
+  // Only create a new file if the content has changed or the original file got lost.
+  $dest = $dir .'/'. $language->language .'_'. $data_hash .'.js';
+  if ($data && ($changed_hash || !file_exists($dest))) {
     // Ensure that the directory exists and is writable, if possible.
     file_check_directory($dir, TRUE);
 
     // Save the file.
-    $dest = $dir . '/' . $language->language . '_' . $data_hash . '.js';
     if (file_unmanaged_save_data($data, $dest)) {
       $language->javascript = $data_hash;
-      $status = ($status == 'deleted') ? 'updated' : 'created';
+      $status = ($status == 'deleted') ? 'updated' : ($changed_hash ? 'created' : 'rebuilt');
     }
     else {
       $language->javascript = '';
@@ -2421,8 +2423,9 @@
   }
 
   // Save the new JavaScript hash (or an empty value if the file
-  // just got deleted). Act only if some operation was executed.
-  if ($status) {
+  // just got deleted). Act only if some operation was executed that 
+  // changed the hash code.
+  if ($status && $changed_hash) {
     db_update('languages')
       ->field(array(
         'javascript' => $language->javascript,
@@ -2445,6 +2448,9 @@
     case 'updated':
       watchdog('locale', 'Updated JavaScript translation file for the language %language.', array('%language' => t($language->name)));
       return TRUE;
+    case 'rebuilt':
+      watchdog('locale', 'JavaScript translation file %file.js was lost.', array('%file' => $language->javascript), WATCHDOG_WARNING);
+      // Let slip through.      
     case 'created':
       watchdog('locale', 'Created JavaScript translation file for the language %language.', array('%language' => t($language->name)));
       return TRUE;
Index: modules/locale/locale.test
===================================================================
RCS file: /cvs/drupal/drupal/modules/locale/locale.test,v
retrieving revision 1.19
diff -u -r1.19 locale.test
--- modules/locale/locale.test	24 Feb 2009 16:46:52 -0000	1.19
+++ modules/locale/locale.test	21 Mar 2009 00:00:03 -0000
@@ -522,6 +522,31 @@
     $this->drupalPost('admin/build/translate/translate', $search, t('Filter'));
     $this->assertText(t('No strings found for your search.'), t("Search didn't find the invalid string."));
   }
+  
+  function testJavaScriptTranslation() {
+    $user = $this->drupalCreateUser(array('translate interface', 'administer languages', 'access administration pages'));
+    $this->drupalLogin($user);
+    
+    // Add French language.
+    $this->drupalPost('admin/settings/language/add', array('langcode' => $langcode = 'fr'), t('Add language'));
+    
+    // Build the JavaScript translation file for French.
+    $this->drupalGet('admin/build/translate/translate');
+    $string = db_fetch_object(db_query('SELECT min(lid) AS lid FROM {locales_source} WHERE location LIKE \'%.js%\' AND textgroup = \'default\''));
+    $edit = array('translations['. $langcode .']' => 'french translation');
+    $this->drupalPost('admin/build/translate/edit/' . $string->lid, $edit, t('Save translations'));
+    locale_inc_callback('_locale_rebuild_js', $langcode);
+    $file = db_fetch_object(db_query('SELECT javascript FROM {languages} WHERE language = \'%s\'', $langcode));
+    $js_file = file_create_path(variable_get('locale_js_directory', 'languages')) . '/'. $langcode .'_' . $file->javascript . '.js';
+    $this->assertTrue($result = file_exists($js_file), t('JavaScript file created: %file', array('%file' => $result ? $js_file : t('not found'))));
+            
+    // Test JavaScript translation rebuilding.
+    file_unmanaged_delete($js_file);
+    $this->assertTrue($result = !file_exists($js_file), t('JavaScript file deleted: %file', array('%file' => $result ? $js_file : t('found'))));
+    cache_clear_all();
+    locale_inc_callback('_locale_rebuild_js', $langcode);
+    $this->assertTrue($result = file_exists($js_file), t('JavaScript file rebuilt: %file', array('%file' => $result ? $js_file : t('not found'))));
+  }
 }
 
 /**