Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.932
diff -u -p -r1.932 common.inc
--- includes/common.inc	10 Jul 2009 05:45:56 -0000	1.932
+++ includes/common.inc	12 Jul 2009 23:30:18 -0000
@@ -2122,19 +2122,23 @@ function url($path = NULL, array $option
 /**
  * Format an attribute string to insert in a tag.
  *
+ * Each array key and its value will be formatted into an HTML attribute string.
+ * If a value is itself an array, then each array element is concatenated with a
+ * space between each value (e.g. a multi-value class attribute).
+ *
  * @param $attributes
  *   An associative array of HTML attributes.
  * @return
  *   An HTML string ready for insertion in a tag.
  */
 function drupal_attributes($attributes = array()) {
-  if (is_array($attributes)) {
-    $t = '';
-    foreach ($attributes as $key => $value) {
-      $t .= " $key=" . '"' . check_plain($value) . '"';
+  foreach ($attributes as $attribute => $data) {
+    if (is_array($data)) {
+      $data = implode(' ', $data);
     }
-    return $t;
+    $items[] = $attribute . '="' . check_plain($data) . '"';
   }
+  return isset($items) ? ' ' . implode(' ', $items) : '';
 }
 
 /**
@@ -4100,7 +4104,7 @@ function drupal_common_theme() {
       'arguments' => array('links' => NULL, 'attributes' => array('class' => 'links')),
     ),
     'image' => array(
-      'arguments' => array('path' => NULL, 'alt' => '', 'title' => '', 'attributes' => NULL, 'getsize' => TRUE),
+      'arguments' => array('path' => NULL, 'alt' => '', 'title' => '', 'attributes' => array(), 'getsize' => TRUE),
     ),
     'breadcrumb' => array(
       'arguments' => array('breadcrumb' => NULL),
@@ -4124,7 +4128,7 @@ function drupal_common_theme() {
       'arguments' => array('type' => MARK_NEW),
     ),
     'item_list' => array(
-      'arguments' => array('items' => array(), 'title' => NULL, 'type' => 'ul', 'attributes' => NULL),
+      'arguments' => array('items' => array(), 'title' => NULL, 'type' => 'ul', 'attributes' => array()),
     ),
     'more_help_link' => array(
       'arguments' => array('url' => NULL),
Index: includes/theme.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/theme.inc,v
retrieving revision 1.497
diff -u -p -r1.497 theme.inc
--- includes/theme.inc	2 Jul 2009 04:27:22 -0000	1.497
+++ includes/theme.inc	12 Jul 2009 23:30:19 -0000
@@ -1335,7 +1335,7 @@ function theme_links($links, $attributes
  * @return
  *   A string containing the image tag.
  */
-function theme_image($path, $alt = '', $title = '', $attributes = NULL, $getsize = TRUE) {
+function theme_image($path, $alt = '', $title = '', $attributes = array(), $getsize = TRUE) {
   if (!$getsize || (is_file($path) && (list($width, $height, $type, $image_attributes) = @getimagesize($path)))) {
     $attributes = drupal_attributes($attributes);
     $url = (url($path) == $path) ? $path : (base_path() . $path);
Index: modules/image/image.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/image/image.module,v
retrieving revision 1.1
diff -u -p -r1.1 image.module
--- modules/image/image.module	12 Jul 2009 08:36:34 -0000	1.1
+++ modules/image/image.module	12 Jul 2009 23:30:19 -0000
@@ -29,7 +29,7 @@ function image_menu() {
 function image_theme() {
   return array(
     'image_style' => array(
-      'arguments' => array('style' => NULL, 'path' => NULL, 'alt' => '', 'title' => '', 'attributes' => NULL, 'getsize' => TRUE),
+      'arguments' => array('style' => NULL, 'path' => NULL, 'alt' => '', 'title' => '', 'attributes' => array(), 'getsize' => TRUE),
     ),
   );
 }
@@ -666,7 +666,7 @@ function image_effect_apply(&$image, $ef
  *   A string containing the image tag.
  * @ingroup themeable
  */
-function theme_image_style($style_name, $path, $alt = '', $title = '', $attributes = NULL, $getsize = TRUE) {
+function theme_image_style($style_name, $path, $alt = '', $title = '', $attributes = array(), $getsize = TRUE) {
   // theme_image() can only honor the $getsize parameter with local file paths.
   // The derivative image is not created until it has been requested so the file
   // may not yet exist, in this case we just fallback to the URL.
Index: modules/simpletest/tests/common.test
===================================================================
RCS file: /cvs/drupal/drupal/modules/simpletest/tests/common.test,v
retrieving revision 1.53
diff -u -p -r1.53 common.test
--- modules/simpletest/tests/common.test	10 Jul 2009 05:45:56 -0000	1.53
+++ modules/simpletest/tests/common.test	12 Jul 2009 23:30:19 -0000
@@ -1074,3 +1074,43 @@ class FormatDateUnitTest extends DrupalW
     drupal_save_session(TRUE);
   }
 }
+
+/**
+ * Tests for the format_date() function.
+ */
+class DrupalAttributesUnitTest extends DrupalUnitTestCase {
+  public static function getInfo() {
+    return array(
+      'name' => t('HTML Attributes'),
+      'description' => t('Perform unit tests on the drupal_attributes() function.'),
+      'group' => t('System')
+    );
+  }
+
+  /**
+   * Tests that drupal_css_class() cleans the class name properly.
+   */
+  function testDrupalAttributes() {
+    // Verify that special characters are HTML encoded.
+    $this->assertIdentical(drupal_attributes(array('title' => '&"\'<>')), ' title="&amp;&quot;&#039;&lt;&gt;"', t('HTML encode attribute values.'));
+
+    // Verify multi-value attributes are concatenated with spaces.
+    $attributes = array('class' => array('first', 'last'));
+    $this->assertIdentical(drupal_attributes(array('class' => array('first', 'last'))), ' class="first last"', t('Concatenate multi-value attributes.'));
+
+    // Verify empty attribute values are rendered.
+    $this->assertIdentical(drupal_attributes(array('alt' => '')), ' alt=""', t('Empty attribute value #1.'));
+    $this->assertIdentical(drupal_attributes(array('alt' => NULL)), ' alt=""', t('Empty attribute value #2.'));
+
+    // Verify multiple attributes are rendered.
+    $attributes = array(
+      'id' => 'id-test',
+      'class' => array('first', 'last'),
+      'alt' => 'Alternate',
+    );
+    $this->assertIdentical(drupal_attributes($attributes), ' id="id-test" class="first last" alt="Alternate"', t('Multiple attributes.'));
+
+    // Verify empty attributes array is rendered.
+    $this->assertIdentical(drupal_attributes(array()), '', t('Empty attributes array.'));
+  }
+}
Index: modules/user/user.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/user/user.module,v
retrieving revision 1.1011
diff -u -p -r1.1011 user.module
--- modules/user/user.module	12 Jul 2009 08:36:35 -0000	1.1011
+++ modules/user/user.module	12 Jul 2009 23:30:19 -0000
@@ -1177,10 +1177,10 @@ function template_preprocess_user_pictur
     if (isset($filepath)) {
       $alt = t("@user's picture", array('@user' => $account->name ? $account->name : variable_get('anonymous', t('Anonymous'))));
       if (module_exists('image') && $style = variable_get('user_picture_style', '')) {
-        $variables['picture'] = theme('image_style', $style, $filepath, $alt, $alt, NULL, FALSE);
+        $variables['picture'] = theme('image_style', $style, $filepath, $alt, $alt, array(), FALSE);
       }
       else {
-        $variables['picture'] = theme('image', $filepath, $alt, $alt, NULL, FALSE);
+        $variables['picture'] = theme('image', $filepath, $alt, $alt, array(), FALSE);
       }
       if (!empty($account->uid) && user_access('access user profiles')) {
         $attributes = array('attributes' => array('title' => t('View user profile.')), 'html' => TRUE);