Index: modules/poll/poll.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/poll/poll.module,v
retrieving revision 1.292
diff -u -r1.292 poll.module
--- modules/poll/poll.module	26 Apr 2009 16:31:23 -0000	1.292
+++ modules/poll/poll.module	27 Apr 2009 02:30:41 -0000
@@ -246,20 +246,17 @@
   $delta = 0;
   $weight = 0;
   if (isset($node->choice)) {
-    $delta = count($node->choice);
-    $weight = -$delta;
-    foreach ($node->choice as $chid => $choice) {
-      $key = 'chid:' . $chid;
-      $form['choice_wrapper']['choice'][$key] = _poll_choice_form($key, $choice['chid'], $choice['chtext'], $choice['chvotes'], $choice['weight'], $choice_count);
+    foreach ($node->choice as $choice) {
+      $choice['chid'] = isset($choice['chid']) ? $choice['chid'] : NULL;
+      $form['choice_wrapper']['choice'][$delta] = _poll_choice_form($delta, $choice['chid'], $choice['chtext'], $choice['chvotes'], $choice['weight'], $choice_count);
       $weight = ($choice['weight'] > $weight) ? $choice['weight'] : $weight;
+      $delta++;
     }
   }
 
   // Add initial or additional choices.
-  $existing_delta = $delta;
   for ($delta; $delta < $choice_count; $delta++) {
-    $key = 'new:' . ($delta - $existing_delta);
-    $form['choice_wrapper']['choice'][$key] = _poll_choice_form($key, NULL, '', 0, $weight, $choice_count);
+    $form['choice_wrapper']['choice'][$delta] = _poll_choice_form($delta, NULL, '', 0, $weight, $choice_count);
   }
 
   // We name our button 'poll_more' to avoid conflicts with other modules using
@@ -270,6 +267,8 @@
     '#description' => t("If the amount of boxes above isn't enough, click here to add more choices."),
     '#weight' => 1,
     '#submit' => array('poll_more_choices_submit'), // If no javascript action.
+    '#validate' => array(), // No form-level validation for this button.
+    '#validate_section' => array('choice_wrapper', 'choice'),
     '#ahah' => array(
       'callback' => 'poll_choice_js',
       'wrapper' => 'poll-choices',
@@ -315,13 +314,24 @@
  * entire form is rebuilt during the page reload.
  */
 function poll_more_choices_submit($form, &$form_state) {
-  // Set the form to rebuild and run submit handlers.
-  node_form_submit_build_node($form, $form_state);
+  // Non-JavaScript behavior. Entire form is validated and 5 choices are added.
+  // The node must be rebuilt to populate the $node variable for hook_form().
+  if (empty($form['#validate_section_allowed'])) {
+    node_form_submit_build_node($form, $form_state);
+    $new_choices = 5;
+  }
+  // JavaScript behavior. Only the choice section is validated, and 1 choice is
+  // added. We don't need to (and can't) rebuild the node because only the
+  // validated section of the form is given any values.
+  else {
+    $form_state['node']['choice'] = array_values($form_state['values']['choice']);
+    $form_state['rebuild'] = TRUE;
+    $new_choices = 1;
+  }
 
   // Make the changes we want to the form state.
-  if ($form_state['values']['poll_more']) {
-    $n = $_GET['q'] == 'system/ahah' ? 1 : 5;
-    $form_state['choice_count'] = count($form_state['values']['choice']) + $n;
+  if ($form_state['values']['op'] == $form['choice_wrapper']['poll_more']['#value']) {
+    $form_state['choice_count'] = count($form_state['values']['choice']) + $new_choices;
   }
 }
 
Index: modules/poll/poll.test
===================================================================
RCS file: /cvs/drupal/drupal/modules/poll/poll.test,v
retrieving revision 1.17
diff -u -r1.17 poll.test
--- modules/poll/poll.test	26 Apr 2009 16:31:23 -0000	1.17
+++ modules/poll/poll.test	27 Apr 2009 02:30:41 -0000
@@ -60,11 +60,14 @@
     $edit = array(
       'title' => $title
     );
-    foreach ($already_submitted_choices as $k => $text) {
-      $edit['choice[chid:' . $k . '][chtext]'] = $text;
+    $delta = 0;
+    foreach ($already_submitted_choices as $text) {
+      $edit['choice[' . $delta . '][chtext]'] = $text;
+      $delta++;
     }
-    foreach ($new_choices as $k => $text) {
-      $edit['choice[new:' . $k . '][chtext]'] = $text;
+    foreach ($new_choices as $text) {
+      $edit['choice[' . $delta . '][chtext]'] = $text;
+      $delta++;
     }
     return array($edit, count($already_submitted_choices) + count($new_choices));
   }
@@ -183,11 +186,7 @@
     $web_user = $this->drupalCreateUser(array('create poll content', 'access content'));
     $this->drupalLogin($web_user);
     $this->drupalGet('node/add/poll');
-    $edit = array(
-      'title' => $this->randomName(),
-      'choice[new:0][chtext]' => $this->randomName(),
-      'choice[new:1][chtext]' => $this->randomName(),
-    );
+    $edit = array();
 
     // @TODO: the framework should make it possible to submit a form to a
     // different URL than its action or the current. For now, we can just force
@@ -206,8 +205,8 @@
 
     // Needs to be emptied out so the new content will be parsed.
     $this->elements = '';
-    $this->assertFieldByName('choice[chid:0][chtext]', $edit['choice[new:0][chtext]'], t('Field !i found', array('!i' => 0)));
-    $this->assertFieldByName('choice[chid:1][chtext]', $edit['choice[new:1][chtext]'], t('Field !i found', array('!i' => 1)));
-    $this->assertFieldByName('choice[new:0][chtext]', '', t('Field !i found', array('!i' => 2)));
+    $this->assertFieldByName('choice[0][chtext]', '', t('Field !i found', array('!i' => 0)));
+    $this->assertFieldByName('choice[1][chtext]', '', t('Field !i found', array('!i' => 1)));
+    $this->assertFieldByName('choice[2][chtext]', '', t('Field !i found', array('!i' => 2)));
   }
 }
Index: modules/simpletest/tests/form.test
===================================================================
RCS file: /cvs/drupal/drupal/modules/simpletest/tests/form.test,v
retrieving revision 1.8
diff -u -r1.8 form.test
--- modules/simpletest/tests/form.test	22 Apr 2009 09:12:44 -0000	1.8
+++ modules/simpletest/tests/form.test	27 Apr 2009 02:30:42 -0000
@@ -69,8 +69,111 @@
         $this->assertTrue(isset($errors[$element]), "Check empty($key) '$type' field '$element'");
       }
     }
-    // Clear the expected form error messages so they don't appear as exceptions.
+    // Clear errors and messages.
     drupal_get_messages();
+    form_set_error(NULL, '', TRUE);
+  }
+
+  /**
+   * Validate a section of a form but not others.
+   *
+   * If the validated form fields are found in form_get_errors() and the
+   * non-validated field is not found then the test passes.
+   */
+  function testValidateSection() {
+    // A list of elements that will intentionally fail validation.
+    $validated_elements = array(
+      $this->randomName(),
+      $this->randomName(),
+    );
+
+    // A list of elements that will intentionally be skipped in validation.
+    $skipped_elements = array(
+      $this->randomName(),
+    );
+
+    // A fieldset to test validation within a nested field.
+    $fieldset = $this->randomName();
+
+    // Test both with a #submit handler and without one.
+    // The #submit property is required when using #validate_section.
+    $ops = array(
+      'with_submit' => array(
+        '#type' => 'submit',
+        '#value' => t('Submit'),
+        '#validate_section' => array($fieldset),
+        '#test_skipped_elements' => drupal_map_assoc($skipped_elements),
+        '#test_validate_elements' => drupal_map_assoc($validated_elements),
+        '#submit' => array(), // Required!
+      ),
+      'without_submit' => array(
+        '#type' => 'submit',
+        '#value' => t('Submit'),
+        '#validate_section' => array($fieldset),
+        '#test_skipped_elements' => array(),
+        '#test_validate_elements' => drupal_map_assoc(array_merge($skipped_elements, $validated_elements)),
+      ),
+    );
+
+    foreach ($ops as $test => $op) {
+      $form = array();
+      $form[$skipped_elements[0]] = array(
+        '#type' => 'textfield',
+        '#required' => TRUE,
+      );
+      $form[$fieldset] = array(
+        '#type' => 'fieldset',
+        '#tree' => TRUE,
+      );
+      $form[$fieldset][$validated_elements[0]] = array(
+        '#type' => 'textfield',
+        '#required' => TRUE,
+      );
+      $form[$fieldset][$this->randomName()][$validated_elements[1]] = array(
+        '#type' => 'textfield',
+        '#required' => TRUE,
+      );
+      $form['op'] = $op;
+
+      $form_id = $this->randomName();
+      $form_state = array();
+      $form_state['values'] = array(
+        'op' => t('Submit'),
+      );
+
+      $form['#post'] = $form_state['values'];
+      $form['#post']['form_id'] = $form_id;
+      drupal_prepare_form($form_id, $form, $form_state);
+      drupal_process_form($form_id, $form, $form_state);
+      $errors = form_get_errors();
+
+      $skipped = $op['#test_skipped_elements'];
+      $validated = array();
+      foreach ($errors as $element_tree => $error) {
+        foreach ($op['#test_validate_elements'] as $element) {
+          if (strpos($element_tree, $element) !== FALSE) {
+            $validated[$element] = $element;
+          }
+        }
+        foreach ($op['#test_skipped_elements'] as $element) {
+          if (strpos($element_tree, $element) !== FALSE) {
+            unset($skipped[$element]);
+          }
+        }
+      }
+      if ($test == 'with_submit') {
+        $this->assertTrue($skipped == $op['#test_skipped_elements'], "Form element validation intentionally skipped on a portion of the form.");
+        $this->assertTrue($validated == $op['#test_validate_elements'], "All elements within the validated section successfully validated.");
+      }
+      elseif ($test == 'without_submit') {
+        $this->assertTrue($skipped == $op['#test_skipped_elements'], "No elements were skipped because the button #submit property is not set.");
+        $this->assertTrue($validated == $op['#test_validate_elements'], "The entire form was validated because the button #submit property is not set.");
+      }
+
+      // Clear errors and messages.
+      drupal_get_messages();
+      form_set_error(NULL, '', TRUE);
+    }
   }
 }
 
Index: includes/form.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/form.inc,v
retrieving revision 1.328
diff -u -r1.328 form.inc
--- includes/form.inc	22 Apr 2009 09:12:44 -0000	1.328
+++ includes/form.inc	27 Apr 2009 02:30:41 -0000
@@ -668,13 +668,26 @@
   // If the session token was set by drupal_prepare_form(), ensure that it
   // matches the current user's session.
   if (isset($form['#token'])) {
-    if (!drupal_valid_token($form_state['values']['form_token'], $form['#token'])) {
+    if (!drupal_valid_token($form['form_token']['#value'], $form['#token'])) {
       // Setting this error will cause the form to fail validation.
       form_set_error('form_token', t('Validation error, please try again. If this error persists, please contact the site administrator.'));
     }
   }
 
-  _form_validate($form, $form_state, $form_id);
+  // Allow only a portion of the form to be validated. This is only allowed if
+  // the #validate_section property is on a button AND a custom #submit property
+  // is defined. This prevents the form-level submit handlers from firing
+  // accidentally when a portion of the form has not been validated.
+  $elements = $form;
+  $button = isset($form_state['clicked_button']) ? $form_state['clicked_button'] : FALSE;
+  if ($button && !empty($form['#validate_section_allowed']) && isset($button['#validate_section']) && isset($button['#submit'])) {
+    foreach ($button['#validate_section'] as $section) {
+      $elements = $elements[$section];
+    }
+  }
+
+  // Validate the section of the form.
+  _form_validate($elements, $form_state, $form, TRUE);
   $validated_forms[$form_id] = TRUE;
 }
 
@@ -745,7 +758,7 @@
  * list of options given to the user. Then calls user-defined validators.
  *
  * @param $elements
- *   An associative array containing the structure of the form.
+ *   An associative array containing the structure of a form section.
  * @param $form_state
  *   A keyed array containing the current state of the form. The current
  *   user-submitted data is stored in $form_state['values'], though
@@ -756,20 +769,24 @@
  *   This technique is useful when validation requires file parsing,
  *   web service requests, or other expensive requests that should
  *   not be repeated in the submission step.
- * @param $form_id
- *   A unique string identifying the form for validation, submission,
- *   theming, and hook_form_alter functions.
+ * @param $complete_form
+ *   An associative array containing the structure of the entire form.
+ * @param $init
+ *   Boolean value to indicate if we're starting a new validate operation.
  */
-function _form_validate($elements, &$form_state, $form_id = NULL) {
-  static $complete_form;
-
+function _form_validate($elements, &$form_state, $complete_form, $init = FALSE) {
   // Also used in the installer, pre-database setup.
   $t = get_t();
 
   // Recurse through all children.
   foreach (element_children($elements) as $key) {
     if (isset($elements[$key]) && $elements[$key]) {
-      _form_validate($elements[$key], $form_state);
+      // Only validated elements receive a value.
+      if (isset($elements[$key]['#value'])) {
+        form_set_value($elements[$key], $elements[$key]['#value'], $form_state);
+      }
+
+      _form_validate($elements[$key], $form_state, $complete_form);
     }
   }
   // Validate the current input.
@@ -814,9 +831,8 @@
     // Call user-defined form level validators and store a copy of the full
     // form so that element-specific validators can examine the entire structure
     // if necessary.
-    if (isset($form_id)) {
-      form_execute_handlers('validate', $elements, $form_state);
-      $complete_form = $elements;
+    if ($init) {
+      form_execute_handlers('validate', $complete_form, $form_state);
     }
     // Call any element-specific validators. These must act on the element
     // #value data.
@@ -1165,7 +1181,6 @@
       }
     }
   }
-  form_set_value($form, $form['#value'], $form_state);
 }
 
 /**
@@ -1825,6 +1840,9 @@
   // We will run some of the submit handlers so we need to disable redirecting.
   $form['#redirect'] = FALSE;
 
+  // Use the validate section handling on the clicked button (if available).
+  $form['#validate_section_allowed'] = TRUE;
+
   // We need to process the form, prepare for that by setting a few internals
   // variables.
   $form_state['input'] = $_POST;