Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.1013
diff -u -r1.1013 common.inc
--- includes/common.inc	11 Oct 2009 06:05:53 -0000	1.1013
+++ includes/common.inc	12 Oct 2009 13:52:13 -0000
@@ -2578,6 +2578,91 @@
  *   an HTML string containing a link to the given path.
  */
 function l($text, $path, array $options = array()) {
+  global $theme;
+  static $theme_function;
+  static $processor_functions = array();
+
+  $variables = array(
+    'text' => $text,
+    'path' => $path,
+    'options' => $options,
+  );
+
+  // Basically, we want to call theme('link', $variables). But we can't do that
+  // until the theme system is fully loaded and operational, and even when it
+  // is, it has too much overhead (l() is called a lot!). So instead, we use
+  // static variables to cache the theme function to call (yes, we're assuming
+  // a function, because a template implementation of 'link' would be needlessly
+  // slow) and its preprocess and process functions. In a sense, we're
+  // duplicating what theme() does in order to shave a few microseconds.
+  if (!isset($theme_function)) {
+    if (isset($theme)) {
+      // Theme hooks can have include files, but those only need to be loaded
+      // once per page request. No need to duplicate that part of theme().
+      // One more call to theme() per page request is fine. Additional calls
+      // to l() per page request will avoid this overhead.
+      $return = theme('link', $variables);
+
+      $hooks = theme_get_registry();
+      if (isset($hooks) && isset($hooks['link']) && isset($hooks['link']['function'])) {
+        $theme_function = $hooks['link']['function'];
+        foreach (array('preprocess functions', 'process functions') as $phase) {
+          if (isset($hooks['link'][$phase])) {
+            $processor_functions = array_merge($processor_functions, $hooks['link'][$phase]);
+          }
+        }
+      }
+      // Now that everything is loaded, cleanup our data to minimize overhead.
+      foreach ($processor_functions as $key => $function) {
+        if (!function_exists($function)) {
+          unset($processor_functions[$key]);
+        }
+      }
+      if (!function_exists($theme_function)) {
+        $theme_function = 'theme_link';
+      }
+
+      return $return;
+    }
+  }
+
+  // Here we've already called theme('link') once for the page request and
+  // are on a subsequent call to l(). So we emulate what theme() would do
+  // with respect to preprocess and process functions.
+  foreach ($processor_functions as $function) {
+    $function($variables, 'link');
+  }
+  // Now, call the actual function. Chances are, it's not overridden by the
+  // theme, and if so, save the overhead of a function_exists() and calling
+  // a variable function.
+  if (!isset($theme_function) || $theme_function == 'theme_link') {
+    return theme_link($variables);
+  }
+  else {
+    return $theme_function($variables);
+  }
+}
+
+/**
+ * Format an internal Drupal link.
+ *
+ * @param $variables
+ *   A keyed array with 'text', 'path', and 'options'.
+ *   @see l() for documentation about these.
+ * 
+ * @return
+ *   an HTML string containing a link to the given path.
+ * 
+ * @ingroup themeable
+ * 
+ * @todo
+ *   If it's never possible for l() to be called without theme.inc loaded,
+ *   then move this function to theme.inc.
+ */
+function theme_link($variables) {
+  $text = $variables['text'];
+  $path = $variables['path'];
+  $options = $variables['options'];
   global $language_url;
 
   // Merge in defaults.
@@ -4857,6 +4942,9 @@
     'status_messages' => array(
       'arguments' => array('display' => NULL),
     ),
+    'link' => array(
+      'arguments' => array('text' => NULL, 'path' => NULL, 'options' => array()),
+    ),
     'links' => array(
       'arguments' => array('links' => NULL, 'attributes' => array('class' => array('links')), 'heading' => array()),
     ),
Index: modules/simpletest/tests/common.test
===================================================================
RCS file: /cvs/drupal/drupal/modules/simpletest/tests/common.test,v
retrieving revision 1.83
diff -u -r1.83 common.test
--- modules/simpletest/tests/common.test	11 Oct 2009 02:14:43 -0000	1.83
+++ modules/simpletest/tests/common.test	12 Oct 2009 13:52:13 -0000
@@ -4,7 +4,7 @@
 /**
  * Tests for URL generation functions.
  */
-class CommonURLUnitTest extends DrupalUnitTestCase {
+class CommonURLUnitTest extends DrupalWebTestCase {
   public static function getInfo() {
     return array(
       'name' => 'URL generation tests',