Index: libraries.api.php
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/libraries/libraries.api.php,v
retrieving revision 1.2
diff -u -p -r1.2 libraries.api.php
--- libraries.api.php	23 Jul 2010 12:57:01 -0000	1.2
+++ libraries.api.php	25 Aug 2010 00:08:53 -0000
@@ -20,6 +20,9 @@
  *   - path: (optional) A relative path from the directory of the library to the
  *     actual library. Only required if the extracted download package contains
  *     the actual library files in a sub-directory.
+ *   - external: (optional) A boolean indicating whether the library contains
+ *     external files. In case of multiple variants, of which some declare
+ *     external files and some do not, set this to TRUE.
  *   - version callback: (optional) The name of a function that detects and
  *     returns the full version string of the library. Defaults to
  *     libraries_get_version(). The first argument is always $library, an array
Index: libraries.module
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/libraries/libraries.module,v
retrieving revision 1.6
diff -u -p -r1.6 libraries.module
--- libraries.module	23 Jul 2010 12:57:01 -0000	1.6
+++ libraries.module	25 Aug 2010 00:08:54 -0000
@@ -146,6 +146,7 @@ function libraries_info($library = NULL)
           'vendor url' => '',
           'download url' => '',
           'path' => '',
+          'external' => FALSE,
           'version callback' => 'libraries_get_version',
           'version arguments' => array(),
           'files' => array(),
@@ -208,7 +209,7 @@ function libraries_detect_library(&$libr
   if (!isset($library['library path'])) {
     $library['library path'] = libraries_get_path($name);
   }
-  if (!file_exists($library['library path'])) {
+  if (!$library['external'] && !file_exists($library['library path'])) {
     $library['error'] = t('%library could not be found.', array('%library' => $library['title']));
     return;
   }
@@ -291,6 +292,9 @@ function libraries_detect_library(&$libr
 function libraries_load($library, $variant = NULL) {
   $library = libraries_info($library);
   libraries_detect_library($library);
+  if (!$library['installed']) {
+    return $library['error'];
+  }
   libraries_load_files($library, $variant);
 }
 
@@ -308,7 +312,7 @@ function libraries_load_files($library, 
 
   // If a variant was specified, override the top-level properties with the
   // variant properties.
-  if (!empty($variant) && !empty($library['variants'][$variant]['installed'])) {
+  if (!empty($variant) && $library['variants'][$variant]['installed']) {
     $library = array_merge($library, $library['variants'][$variant]);
   }