Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.1270
diff -u -p -r1.1270 common.inc
--- includes/common.inc	8 Dec 2010 07:06:27 -0000	1.1270
+++ includes/common.inc	8 Dec 2010 14:09:53 -0000
@@ -4499,10 +4499,14 @@ function drupal_add_library($module, $na
  *
  * @param $module
  *   The name of a module that registered a library.
- * @param $library
- *   The name of a registered library.
+ * @param $name
+ *   (optional) The name of a registered library to retrieve. By default, all
+ *   libraries registered by $module are returned.
+ *
  * @return
- *   The definition of the requested library, if existent, or FALSE.
+ *   The definition of the requested library, if $name was passed and it exists,
+ *   or FALSE if it does not exist. If no $name was passed, an associative array
+ *   of libraries registered by $module is returned (which may be empty).
  *
  * @see drupal_add_library()
  * @see hook_library()
@@ -4511,7 +4515,7 @@ function drupal_add_library($module, $na
  * @todo The purpose of drupal_get_*() is completely different to other page
  *   requisite API functions; find and use a different name.
  */
-function drupal_get_library($module, $name) {
+function drupal_get_library($module, $name = NULL) {
   $libraries = &drupal_static(__FUNCTION__, array());
 
   if (!isset($libraries[$module])) {
@@ -4534,11 +4538,13 @@ function drupal_get_library($module, $na
     }
     $libraries[$module] = $module_libraries;
   }
-  if (empty($libraries[$module][$name])) {
-    $libraries[$module][$name] = FALSE;
+  if (isset($name)) {
+    if (!isset($libraries[$module][$name])) {
+      $libraries[$module][$name] = FALSE;
+    }
+    return $libraries[$module][$name];
   }
-
-  return $libraries[$module][$name];
+  return $libraries[$module];
 }
 
 /**
Index: modules/simpletest/tests/common.test
===================================================================
RCS file: /cvs/drupal/drupal/modules/simpletest/tests/common.test,v
retrieving revision 1.137
diff -u -p -r1.137 common.test
--- modules/simpletest/tests/common.test	30 Nov 2010 06:30:21 -0000	1.137
+++ modules/simpletest/tests/common.test	8 Dec 2010 14:18:14 -0000
@@ -1424,6 +1424,26 @@ class JavaScriptTestCase extends DrupalW
   }
 
   /**
+   * Tests retrieval of libraries via drupal_get_library().
+   */
+  function testGetLibrary() {
+    // Retrieve all libraries registered by a module.
+    $libraries = drupal_get_library('common_test');
+    $this->assertTrue(isset($libraries['farbtastic']), t('Retrieved all module libraries.'));
+    // Retrieve all libraries for a module not implementing hook_library().
+    // Note: This test installs Locale module.
+    $libraries = drupal_get_library('locale');
+    $this->assertEqual($libraries, array(), t('Retrieving libraries from a module not implementing hook_library() returns an emtpy array.'));
+
+    // Retrieve a specific library by module and name.
+    $farbtastic = drupal_get_library('common_test', 'farbtastic');
+    $this->assertEqual($farbtastic['version'], '5.3', t('Retrieved a single library.'));
+    // Retrieve a non-existing library by module and name.
+    $farbtastic = drupal_get_library('common_test', 'foo');
+    $this->assertIdentical($farbtastic, FALSE, t('Retrieving a non-existing library returns FALSE.'));
+  }
+
+  /**
    * Tests that the query string remains intact when adding JavaScript files
    *  that have query string parameters.
    */