- Patch #140783 by sun: a select list without #default_value() always passes form validation.

15 files changed, 353 insertions, 52 deletions

diff --git a/includes/common.inc b/includes/common.inc
index 7671cd0f8..568115a86 100644
--- a/includes/common.inc
+++ b/includes/common.inc
@@ -5619,7 +5619,8 @@ function element_set_attributes(array &$element, array $map) {
     if (is_int($property)) {
       $property = '#' . $attribute;
     }
-    if (isset($element[$property])) {
+    // Do not overwrite already existing attributes.
+    if (isset($element[$property]) && !isset($element['#attributes'][$attribute])) {
       $element['#attributes'][$attribute] = $element[$property];
     }
   }
diff --git a/includes/form.inc b/includes/form.inc
index 6c4ab4d76..5a6ccd20c 100644
--- a/includes/form.inc
+++ b/includes/form.inc
@@ -1142,6 +1142,26 @@ function _form_validate(&$elements, &$form_state, $form_id = NULL) {
             }
           }
         }
+        // Non-multiple select fields always have a value in HTML. If the user
+        // does not change the form, it will be the value of the first option.
+        // Because of this, form validation for the field will almost always
+        // pass, even if the user did not select anything. To work around this
+        // browser behavior, select fields without a #default_value get an
+        // additional, first empty option by default. In case the submitted
+        // value is identical to the empty option's value, we reset the
+        // element's value to NULL to trigger the regular #required handling
+        // below.
+        // @see form_process_select()
+        elseif ($elements['#type'] == 'select' && !$elements['#multiple'] && !isset($elements['#default_value']) && $elements['#value'] === (string) $elements['#empty_value']) {
+          if ($elements['#required']) {
+            $elements['#value'] = NULL;
+            form_set_value($elements, NULL, $form_state);
+          }
+          else {
+            $elements['#value'] = $elements['#empty_value'];
+            form_set_value($elements, $elements['#empty_value'], $form_state);
+          }
+        }
         elseif (!isset($options[$elements['#value']])) {
           form_error($elements, $t('An illegal choice has been detected. Please contact the site administrator.'));
           watchdog('form', 'Illegal choice %choice in %name element.', array('%choice' => $elements['#value'], '%name' => empty($elements['#title']) ? $elements['#parents'][0] : $elements['#title']), WATCHDOG_ERROR);
@@ -1183,13 +1203,27 @@ function _form_validate(&$elements, &$form_state, $form_id = NULL) {
     }
 
     // Make sure a value is passed when the field is required.
-    // A simple call to empty() will not cut it here as some fields, like
-    // checkboxes, can return a valid value of '0'. Instead, check the
-    // length if it's a string, and the item count if it's an array.
-    // An unchecked checkbox has a #value of integer 0, different than string
-    // '0', which could be a valid value.
-    if (isset($elements['#needs_validation']) && $elements['#required'] && (!count($elements['#value']) || (is_string($elements['#value']) && strlen(trim($elements['#value'])) == 0) || $elements['#value'] === 0)) {
-      form_error($elements, $t('!name field is required.', array('!name' => $elements['#title'])));
+    if (isset($elements['#needs_validation']) && $elements['#required']) {
+      // A simple call to empty() will not cut it here as some fields, like
+      // checkboxes, can return a valid value of '0'. Instead, check the
+      // length if it's a string, and the item count if it's an array.
+      // An unchecked checkbox has a #value of integer 0, different than string
+      // '0', which could be a valid value.
+      $is_empty_multiple = (!count($elements['#value']));
+      $is_empty_string = (is_string($elements['#value']) && drupal_strlen(trim($elements['#value'])) == 0);
+      $is_empty_value = ($elements['#value'] === 0);
+      if ($is_empty_multiple || $is_empty_string || $is_empty_value) {
+        // Although discouraged, a #title is not mandatory for form elements. In
+        // case there is no #title, we cannot set a form error message.
+        // Instead of setting no #title, form constructors are encouraged to set
+        // #title_display to 'invisible' to improve accessibility.
+        if (isset($elements['#title'])) {
+          form_error($elements, $t('!name field is required.', array('!name' => $elements['#title'])));
+        }
+        else {
+          form_error($elements);
+        }
+      }
     }
 
     // Call user-defined form level validators.
@@ -2238,6 +2272,99 @@ function _form_options_flatten($array) {
 }
 
 /**
+ * Processes a select list form element.
+ *
+ * This process callback is mandatory for select fields, since all user agents
+ * automatically preselect the first available option of single (non-multiple)
+ * select lists.
+ *
+ * @param $element
+ *   The form element to process. Properties used:
+ *   - #multiple: (optional) Indicates whether one or more options can be
+ *     selected. Defaults to FALSE.
+ *   - #default_value: Must be NULL or not set in case there is no value for the
+ *     element yet, in which case a first default option is inserted by default.
+ *     Whether this first option is a valid option depends on whether the field
+ *     is #required or not.
+ *   - #required: (optional) Whether the user needs to select an option (TRUE)
+ *     or not (FALSE). Defaults to TRUE.
+ *   - #empty_option: (optional) The label to show for the first default option.
+ *     By default, the label is automatically set to "- Please select -" for a
+ *     required field and "- None -" for an optional field.
+ *   - #empty_value: (optional) The value for the first default option, which is
+ *     used to determine whether the user submitted a value or not. Defaults to
+ *     '' (an empty string). To be used in case the field is optional and the
+ *     empty default value should have a special value (e.g., a constant).
+ *
+ * @see _form_validate()
+ */
+function form_process_select($element) {
+  // #multiple select fields need a special #name.
+  if ($element['#multiple']) {
+    $element['#attributes']['multiple'] = 'multiple';
+    $element['#attributes']['name'] = $element['#name'] . '[]';
+    // If not explicitly set, #required has to default to FALSE (see below).
+    if (!isset($element['#required'])) {
+      $element['#required'] = FALSE;
+    }
+  }
+  // A non-#multiple select needs special handling to prevent user agents from
+  // preselecting the first option without intention. #multiple select lists do
+  // not get an empty option, as it would not make sense, user interface-wise.
+  else {
+    $add_empty_option = FALSE;
+    // Select elements always have a value in HTML, so the expectation is that
+    // the user has to choose an option. Therefore, a select element is set to
+    // #required TRUE, unless it has been explicitly set to FALSE. This differs
+    // from every other element which gets a default of #required FALSE via
+    // form_builder(). To avoid this default, system_element_info() sets
+    // #required to NULL.
+    // If #required has been explicitly set to FALSE, the user may optionally
+    // choose an option, which can be "None".
+    if (isset($element['#required']) && !$element['#required']) {
+      $element['#required'] = FALSE;
+      $element += array(
+        '#empty_value' => '',
+        '#empty_option' => t('- None -'),
+      );
+      $add_empty_option = TRUE;
+    }
+    // Otherwise, if #required is TRUE (or not set) and there is no
+    // #default_value, then the user has to choose an option, which makes this
+    // element #required.
+    elseif (!isset($element['#default_value'])) {
+      // By only conditionally setting #required to TRUE, we additionally ensure
+      // that the select element does not get a required marker if it already
+      // has a value.
+      $element['#required'] = TRUE;
+      $element += array(
+        '#empty_value' => '',
+        '#empty_option' => t('- Select -'),
+      );
+      $add_empty_option = TRUE;
+    }
+    // If there is a #default_value and #required is not explicitly FALSE, then
+    // there is no point in adding an empty option which is never valid, and we
+    // just retain API compatibility.
+    if (!isset($element['#required'])) {
+      $element['#required'] = FALSE;
+    }
+    // If one of the above conditions is met, add a first empty default option,
+    // which is always invalid for #required select lists that do not specify a
+    // #default_value.
+    // @see _form_validate()
+    if ($add_empty_option) {
+      // The empty option is prepended to #options and purposively not merged
+      // to prevent another option in #options mistakenly using the same value
+      // as #empty_value.
+      $empty_option = array($element['#empty_value'] => $element['#empty_option']);
+      $element['#options'] = $empty_option + $element['#options'];
+    }
+  }
+  return $element;
+}
+
+/**
  * Returns HTML for a select form element.
  *
  * It is possible to group options together; to do this, change the format of
@@ -2257,11 +2384,6 @@ function theme_select($variables) {
   element_set_attributes($element, array('id', 'name', 'size'));
   _form_set_class($element, array('form-select'));
 
-  if (!empty($element['#multiple'])) {
-    $element['#attributes']['multiple'] = 'multiple';
-    $element['#attributes']['name'] .= '[]';
-  }
-
   return '<select' . drupal_attributes($element['#attributes']) . '>' . form_select_options($element) . '</select>';
 }
 
diff --git a/includes/install.core.inc b/includes/install.core.inc
index 56f3e4091..b6dd5f1b3 100644
--- a/includes/install.core.inc
+++ b/includes/install.core.inc
@@ -1749,11 +1749,11 @@ function _install_configure_form($form, &$form_state, &$install_state) {
   );
 
   $countries = country_get_list();
-  $countries = array_merge(array('' => st('No default country')), $countries);
   $form['server_settings']['site_default_country'] = array(
     '#type' => 'select',
     '#title' => t('Default country'),
-    '#default_value' => variable_get('site_default_country', ''),
+    '#required' => FALSE,
+    '#default_value' => variable_get('site_default_country', NULL),
     '#options' => $countries,
     '#description' => st('Select the default country for the site.'),
     '#weight' => 0,
diff --git a/modules/aggregator/aggregator.processor.inc b/modules/aggregator/aggregator.processor.inc
index 2888e2fa6..a7a87dd15 100644
--- a/modules/aggregator/aggregator.processor.inc
+++ b/modules/aggregator/aggregator.processor.inc
@@ -70,7 +70,7 @@ function aggregator_aggregator_remove($feed) {
 function aggregator_form_aggregator_admin_form_alter(&$form, $form_state) {
   if (in_array('aggregator', variable_get('aggregator_processors', array('aggregator')))) {
     $info = module_invoke('aggregator', 'aggregator_process', 'info');
-    $items = array(0 => t('none')) + drupal_map_assoc(array(3, 5, 10, 15, 20, 25), '_aggregator_items');
+    $items = drupal_map_assoc(array(3, 5, 10, 15, 20, 25), '_aggregator_items');
     $period = drupal_map_assoc(array(3600, 10800, 21600, 32400, 43200, 86400, 172800, 259200, 604800, 1209600, 2419200, 4838400, 9676800), 'format_interval');
     $period[AGGREGATOR_CLEAR_NEVER] = t('Never');
 
@@ -90,8 +90,10 @@ function aggregator_form_aggregator_admin_form_alter(&$form, $form_state) {
 
     $form['modules']['aggregator']['aggregator_summary_items'] = array(
       '#type' => 'select',
-      '#title' => t('Number of items shown in listing pages') ,
+      '#title' => t('Number of items shown in listing pages'),
+      '#required' => FALSE,
       '#default_value' => variable_get('aggregator_summary_items', 3),
+      '#empty_value' => 0,
       '#options' => $items,
     );
 
diff --git a/modules/block/block.admin.inc b/modules/block/block.admin.inc
index c47a5a7d9..db5b72100 100644
--- a/modules/block/block.admin.inc
+++ b/modules/block/block.admin.inc
@@ -85,9 +85,6 @@ function block_admin_display_form($form, &$form_state, $blocks, $theme, $block_r
     $block_regions = system_region_list($theme, REGIONS_VISIBLE);
   }
 
-  // We always add a region for disabled blocks.
-  $block_regions += array(BLOCK_REGION_NONE => '<' . t('none') . '>');
-
   // Weights range from -delta to +delta, so delta should be at least half
   // of the amount of blocks present. This makes sure all blocks in the same
   // region get an unique weight.
@@ -100,7 +97,8 @@ function block_admin_display_form($form, &$form_state, $blocks, $theme, $block_r
   );
   $form['block_regions'] = array(
     '#type' => 'value',
-    '#value' => $block_regions,
+    // Add a last region for disabled blocks.
+    '#value' => $block_regions + array(BLOCK_REGION_NONE => BLOCK_REGION_NONE),
   );
   $form['blocks'] = array();
   $form['#tree'] = TRUE;
@@ -127,13 +125,15 @@ function block_admin_display_form($form, &$form_state, $blocks, $theme, $block_r
       '#default_value' => $block['weight'],
       '#delta' => $weight_delta,
       '#title_display' => 'invisible',
-      '#title' => t('Weight for @block block', array('%block' => $block['info'])),
+      '#title' => t('Weight for @block block', array('@block' => $block['info'])),
     );
     $form['blocks'][$key]['region'] = array(
       '#type' => 'select',
-      '#default_value' => $block['region'],
+      '#required' => FALSE,
+      '#default_value' => $block['region'] != BLOCK_REGION_NONE ? $block['region'] : NULL,
+      '#empty_value' => BLOCK_REGION_NONE,
       '#title_display' => 'invisible',
-      '#title' => t('Region for @block block', array('%block' => $block['info'])),
+      '#title' => t('Region for @block block', array('@block' => $block['info'])),
       '#options' => $block_regions,
     );
     $form['blocks'][$key]['configure'] = array(
@@ -150,7 +150,7 @@ function block_admin_display_form($form, &$form_state, $blocks, $theme, $block_r
     }
   }
   // Do not allow disabling the main system content block.
-  unset($form['blocks']['system_main']['region']['#options'][BLOCK_REGION_NONE]);
+  $form['blocks']['system_main']['region']['#required'] = TRUE;
 
   $form['actions'] = array(
     '#tree' => FALSE,
@@ -302,9 +302,10 @@ function block_admin_configure($form, &$form_state, $module, $delta) {
       $form['regions'][$key] = array(
         '#type' => 'select',
         '#title' => $theme->info['name'],
-        '#default_value' => (!empty($region) ? $region : BLOCK_REGION_NONE),
-        '#options' => array(BLOCK_REGION_NONE => t('<none>')) + system_region_list($key, REGIONS_VISIBLE),
-        '#expandable' => ($key !== $theme_default),
+        '#required' => FALSE,
+        '#default_value' => !empty($region) && $region != -1 ? $region : NULL,
+        '#empty_value' => BLOCK_REGION_NONE,
+        '#options' => system_region_list($key, REGIONS_VISIBLE),
         '#weight' => ($key == $theme_default ? 9 : 10),
       );
     }
@@ -657,7 +658,7 @@ function template_preprocess_block_admin_display_form(&$variables) {
     $block = &$variables['form']['blocks'][$i];
 
     // Fetch the region for the current block.
-    $region = $block['region']['#default_value'];
+    $region = (isset($block['region']['#default_value']) ? $block['region']['#default_value'] : BLOCK_REGION_NONE);
 
     // Set special classes needed for table drag and drop.
     $block['region']['#attributes']['class'] = array('block-region-select', 'block-region-' . $region);
diff --git a/modules/field_ui/field_ui.admin.inc b/modules/field_ui/field_ui.admin.inc
index 7ce490363..7cf0000b3 100644
--- a/modules/field_ui/field_ui.admin.inc
+++ b/modules/field_ui/field_ui.admin.inc
@@ -304,7 +304,7 @@ function field_ui_field_overview_form($form, &$form_state, $entity_type, $bundle
       t('Widget'),
       array('data' => t('Operations'), 'colspan' => 2),
     ),
-    '#parent_options' => array('' => t('<none>')),
+    '#parent_options' => array(),
     '#regions' => array(
       'main' => array(),
       'add_new' => array('title' => '&nbsp;'),
@@ -335,6 +335,7 @@ function field_ui_field_overview_form($form, &$form_state, $entity_type, $bundle
       'parent_wrapper' => array(
         'parent' => array(
           '#type' => 'select',
+          '#required' => FALSE,
           '#options' => $table['#parent_options'],
           '#attributes' => array('class' => array('field-parent')),
           '#parents' => array('fields', $name, 'parent'),
@@ -401,6 +402,7 @@ function field_ui_field_overview_form($form, &$form_state, $entity_type, $bundle
       'parent_wrapper' => array(
         'parent' => array(
           '#type' => 'select',
+          '#required' => FALSE,
           '#options' => $table['#parent_options'],
           '#attributes' => array('class' => array('field-parent')),
           '#parents' => array('fields', $name, 'parent'),
@@ -432,8 +434,6 @@ function field_ui_field_overview_form($form, &$form_state, $entity_type, $bundle
   $field_type_options = field_ui_field_type_options();
   $widget_type_options = field_ui_widget_type_options(NULL, TRUE);
   if ($field_type_options && $widget_type_options) {
-    array_unshift($field_type_options, t('- Select a field type -'));
-    array_unshift($widget_type_options, t('- Select a widget -'));
     $name = '_add_new_field';
     $table[$name] = array(
       '#attributes' => array('class' => array('draggable', 'tabledrag-leaf', 'add-new')),
@@ -458,6 +458,7 @@ function field_ui_field_overview_form($form, &$form_state, $entity_type, $bundle
       'parent_wrapper' => array(
         'parent' => array(
           '#type' => 'select',
+          '#required' => FALSE,
           '#options' => $table['#parent_options'],
           '#attributes' => array('class' => array('field-parent')),
           '#prefix' => '<div class="add-new-placeholder">&nbsp;</div>',
@@ -481,14 +482,18 @@ function field_ui_field_overview_form($form, &$form_state, $entity_type, $bundle
       ),
       'type' => array(
         '#type' => 'select',
+        '#required' => FALSE,
         '#options' => $field_type_options,
+        '#empty_option' => t('- Select a field type -'),
         '#description' => t('Type of data to store.'),
         '#attributes' => array('class' => array('field-type-select')),
         '#prefix' => '<div class="add-new-placeholder">&nbsp;</div>',
       ),
       'widget_type' => array(
         '#type' => 'select',
+        '#required' => FALSE,
         '#options' => $widget_type_options,
+        '#empty_option' => t('- Select a widget -'),
         '#description' => t('Form element to edit the data.'),
         '#attributes' => array('class' => array('widget-type-select')),
         '#cell_attributes' => array('colspan' => 3),
@@ -500,7 +505,6 @@ function field_ui_field_overview_form($form, &$form_state, $entity_type, $bundle
   // Additional row: add existing field.
   $existing_field_options = field_ui_existing_field_options($entity_type, $bundle);
   if ($existing_field_options && $widget_type_options) {
-    array_unshift($existing_field_options, t('- Select an existing field -'));
     $name = '_add_existing_field';
     $table[$name] = array(
       '#attributes' => array('class' => array('draggable', 'tabledrag-leaf', 'add-new')),
@@ -526,6 +530,7 @@ function field_ui_field_overview_form($form, &$form_state, $entity_type, $bundle
       'parent_wrapper' => array(
         'parent' => array(
           '#type' => 'select',
+          '#required' => FALSE,
           '#options' => $table['#parent_options'],
           '#attributes' => array('class' => array('field-parent')),
           '#prefix' => '<div class="add-new-placeholder">&nbsp;</div>',
@@ -539,7 +544,9 @@ function field_ui_field_overview_form($form, &$form_state, $entity_type, $bundle
       ),
       'field_name' => array(
         '#type' => 'select',
+        '#required' => FALSE,
         '#options' => $existing_field_options,
+        '#empty_option' => t('- Select an existing field -'),
         '#description' => t('Field to share'),
         '#attributes' => array('class' => array('field-select')),
         '#cell_attributes' => array('colspan' => 2),
@@ -547,7 +554,9 @@ function field_ui_field_overview_form($form, &$form_state, $entity_type, $bundle
       ),
       'widget_type' => array(
         '#type' => 'select',
+        '#required' => FALSE,
         '#options' => $widget_type_options,
+        '#empty_option' => t('- Select a widget -'),
         '#description' => t('Form element to edit the data.'),
         '#attributes' => array('class' => array('widget-type-select')),
         '#cell_attributes' => array('colspan' => 3),
@@ -844,7 +853,7 @@ function field_ui_display_overview_form($form, &$form_state, $entity_type, $bund
       'visible' => array('message' => t('No field is displayed.')),
       'hidden' => array('title' => t('Hidden'), 'message' => t('No field is hidden.')),
     ),
-    '#parent_options' => array('' => t('<none>')),
+    '#parent_options' => array(),
     '#attributes' => array(
       'class' => array('field-ui-overview'),
       'id' => 'field-display-overview',
@@ -888,8 +897,8 @@ function field_ui_display_overview_form($form, &$form_state, $entity_type, $bund
       'parent_wrapper' => array(
         'parent' => array(
           '#type' => 'select',
+          '#required' => FALSE,
           '#options' => $table['#parent_options'],
-          '#default_value' => '',
           '#attributes' => array('class' => array('field-parent')),
           '#parents' => array('fields', $name, 'parent'),
         ),
@@ -1042,8 +1051,8 @@ function field_ui_display_overview_form($form, &$form_state, $entity_type, $bund
       'parent_wrapper' => array(
         'parent' => array(
           '#type' => 'select',
+          '#required' => FALSE,
           '#options' => $table['#parent_options'],
-          '#default_value' => '',
           '#attributes' => array('class' => array('field-parent')),
           '#parents' => array('fields', $name, 'parent'),
         ),
diff --git a/modules/image/image.admin.inc b/modules/image/image.admin.inc
index 657781156..9665a8523 100644
--- a/modules/image/image.admin.inc
+++ b/modules/image/image.admin.inc
@@ -116,7 +116,7 @@ function image_style_form($form, &$form_state, $style) {
   }
 
   // Build the new image effect addition form and add it to the effect list.
-  $new_effect_options = array('' => t('Select a new effect'));
+  $new_effect_options = array();
   foreach (image_effect_definitions() as $effect => $definition) {
     $new_effect_options[$effect] = check_plain($definition['label']);
   }
@@ -127,7 +127,9 @@ function image_style_form($form, &$form_state, $style) {
   );
   $form['effects']['new']['new'] = array(
     '#type' => 'select',
+    '#required' => FALSE,
     '#options' => $new_effect_options,
+    '#empty_option' => t('Select a new effect'),
   );
   $form['effects']['new']['weight'] = array(
     '#type' => 'weight',
@@ -291,11 +293,12 @@ function image_style_delete_form($form, $form_state, $style) {
   $form_state['image_style'] = $style;
 
   $replacement_styles = array_diff_key(image_style_options(), array($style['name'] => ''));
-  $replacement_styles[''] = t('No replacement, just delete');
   $form['replacement'] = array(
     '#title' => t('Replacement style'),
     '#type' => 'select',
+    '#required' => FALSE,
     '#options' => $replacement_styles,
+    '#empty_option' => t('No replacement, just delete'),
   );
 
   return confirm_form(
diff --git a/modules/image/image.field.inc b/modules/image/image.field.inc
index b54e601ab..221c5959d 100644
--- a/modules/image/image.field.inc
+++ b/modules/image/image.field.inc
@@ -269,7 +269,8 @@ function image_field_widget_settings_form($field, $instance) {
   $form['preview_image_style'] = array(
     '#title' => t('Preview image style'),
     '#type' => 'select',
-    '#options' => array('' => '<' . t('no preview') . '>') + image_style_options(FALSE),
+    '#required' => FALSE,
+    '#options' => image_style_options(FALSE),
     '#default_value' => $settings['preview_image_style'],
     '#description' => t('The preview image will be shown while editing the content.'),
     '#weight' => 15,
@@ -418,22 +419,24 @@ function image_field_formatter_settings_form($field, $instance, $view_mode, $for
   $display = $instance['display'][$view_mode];
   $settings = $display['settings'];
 
-  $image_styles = array('' => t('None (original image)')) + image_style_options(FALSE);
+  $image_styles = image_style_options(FALSE);
   $form['image_style'] = array(
     '#title' => t('Image style'),
     '#type' => 'select',
+    '#required' => FALSE,
     '#default_value' => $settings['image_style'],
+    '#empty_option' => t('None (original image)'),
     '#options' => $image_styles,
   );
 
   $link_types = array(
-    '' => t('<none>'),
     'content' => t('Content'),
     'file' => t('File'),
   );
   $form['image_link'] = array(
     '#title' => t('Link image to'),
     '#type' => 'select',
+    '#required' => FALSE,
     '#default_value' => $settings['image_link'],
     '#options' => $link_types,
   );
diff --git a/modules/locale/locale.admin.inc b/modules/locale/locale.admin.inc
index 6ca3df30b..9d71ed629 100644
--- a/modules/locale/locale.admin.inc
+++ b/modules/locale/locale.admin.inc
@@ -854,7 +854,9 @@ function locale_translation_filter_form() {
       $form['filters']['status'][$key] = array(
         '#title' => $filter['title'],
         '#type' => 'select',
-        '#multiple' => FALSE,
+        '#required' => FALSE,
+        '#empty_value' => 'all',
+        '#empty_option' => $filter['options']['all'],
         '#size' => 0,
         '#options' => $filter['options'],
       );
diff --git a/modules/menu/menu.admin.inc b/modules/menu/menu.admin.inc
index 2eac43cb3..181f8f5d3 100644
--- a/modules/menu/menu.admin.inc
+++ b/modules/menu/menu.admin.inc
@@ -680,22 +680,24 @@ function menu_configure() {
   $menu_options = menu_get_menus();
 
   $main = variable_get('menu_main_links_source', 'main-menu');
-  $main_options = array_merge($menu_options, array('' => t('No Main links')));
   $form['menu_main_links_source'] = array(
     '#type' => 'select',
     '#title' => t('Source for the Main links'),
+    '#required' => FALSE,
     '#default_value' => variable_get('menu_main_links_source', 'main-menu'),
-    '#options' => $main_options,
+    '#empty_option' => t('No Main links'),
+    '#options' => $menu_options,
     '#tree' => FALSE,
     '#description' => t('Select what should be displayed as the Main links (typically at the top of the page).'),
   );
 
-  $secondary_options = array_merge($menu_options, array('' => t('No Secondary links')));
   $form['menu_secondary_links_source'] = array(
     '#type' => 'select',
     '#title' => t('Source for the Secondary links'),
+    '#required' => FALSE,
     '#default_value' => variable_get('menu_secondary_links_source', 'user-menu'),
-    '#options' => $secondary_options,
+    '#empty_option' => t('No Secondary links'),
+    '#options' => $menu_options,
     '#tree' => FALSE,
     '#description' => t("Select the source for the Secondary links. An advanced option allows you to use the same source for both Main links (currently %main) and Secondary links: if your source menu has two levels of hierarchy, the top level menu links will appear in the Main links, and the children of the active link will appear in the Secondary links." , array('%main' => $main_options[$main])),
   );
diff --git a/modules/simpletest/tests/form.test b/modules/simpletest/tests/form.test
index 969f3f398..793d0c0bf 100644
--- a/modules/simpletest/tests/form.test
+++ b/modules/simpletest/tests/form.test
@@ -153,6 +153,67 @@ class FormsTestCase extends DrupalWebTestCase {
   }
 
   /**
+   * Tests validation of #type 'select' elements.
+   */
+  function testSelect() {
+    $form = $form_state = array();
+    $form = form_test_select($form, $form_state);
+    $error = '!name field is required.';
+    $this->drupalGet('form-test/select');
+
+    // Posting without any values should throw validation errors.
+    $this->drupalPost(NULL, array(), 'Submit');
+    $this->assertNoText(t($error, array('!name' => $form['select']['#title'])));
+    $this->assertNoText(t($error, array('!name' => $form['empty_value']['#title'])));
+    $this->assertNoText(t($error, array('!name' => $form['empty_value_one']['#title'])));
+    $this->assertText(t($error, array('!name' => $form['no_default']['#title'])));
+    $this->assertNoText(t($error, array('!name' => $form['no_default_optional']['#title'])));
+    $this->assertText(t($error, array('!name' => $form['no_default_empty_option']['#title'])));
+    $this->assertNoText(t($error, array('!name' => $form['no_default_empty_option_optional']['#title'])));
+    $this->assertText(t($error, array('!name' => $form['no_default_empty_value']['#title'])));
+    $this->assertText(t($error, array('!name' => $form['no_default_empty_value_one']['#title'])));
+    $this->assertNoText(t($error, array('!name' => $form['no_default_empty_value_optional']['#title'])));
+    $this->assertNoText(t($error, array('!name' => $form['multiple']['#title'])));
+    $this->assertNoText(t($error, array('!name' => $form['multiple_no_default']['#title'])));
+    $this->assertText(t($error, array('!name' => $form['multiple_no_default_required']['#title'])));
+
+    // Post values for required fields.
+    $edit = array(
+      'no_default' => 'three',
+      'no_default_empty_option' => 'three',
+      'no_default_empty_value' => 'three',
+      'no_default_empty_value_one' => 'three',
+      'multiple_no_default_required[]' => 'three',
+    );
+    $this->drupalPost(NULL, $edit, 'Submit');
+    $values = drupal_json_decode($this->drupalGetContent());
+
+    // Verify expected values.
+    $expected = array(
+      'select' => 'one',
+      'empty_value' => 'one',
+      'empty_value_one' => 'one',
+      'no_default' => 'three',
+      'no_default_optional' => '',
+      'no_default_empty_option' => 'three',
+      'no_default_empty_option_optional' => '',
+      'no_default_empty_value' => 'three',
+      'no_default_empty_value_one' => 'three',
+      'no_default_empty_value_optional' => 0,
+      'multiple' => array('two' => 'two'),
+      'multiple_no_default' => array(),
+      'multiple_no_default_required' => array('three' => 'three'),
+    );
+    foreach ($expected as $key => $value) {
+      $this->assertIdentical($values[$key], $value, t('@name: @actual is equal to @expected.', array(
+        '@name' => $key,
+        '@actual' => var_export($values[$key], TRUE),
+        '@expected' => var_export($value, TRUE),
+      )));
+    }
+  }
+
+  /**
    * Test handling of disabled elements.
    *
    * @see _form_test_disabled_elements()
diff --git a/modules/simpletest/tests/form_test.module b/modules/simpletest/tests/form_test.module
index 17988cdaf..ca3538c75 100644
--- a/modules/simpletest/tests/form_test.module
+++ b/modules/simpletest/tests/form_test.module
@@ -92,6 +92,12 @@ function form_test_menu() {
     'access callback' => TRUE,
     'type' => MENU_CALLBACK,
   );
+  $items['form-test/select'] = array(
+    'title' => t('Select'),
+    'page callback' => 'drupal_get_form',
+    'page arguments' => array('form_test_select'),
+    'access callback' => TRUE,
+  );
 
   $items['form-test/disabled-elements'] = array(
     'title' => t('Form test'),
@@ -786,6 +792,94 @@ function _form_test_checkbox_submit($form, &$form_state) {
 }
 
 /**
+ * Builds a form to test #type 'select' validation.
+ */
+function form_test_select($form, &$form_state) {
+  $base = array(
+    '#type' => 'select',
+    '#options' => drupal_map_assoc(array('one', 'two', 'three')),
+  );
+
+  $form['select'] = $base + array(
+    '#title' => '#default_value one',
+    '#default_value' => 'one',
+  );
+  $form['empty_value'] = $base + array(
+    '#title' => '#default_value one, #empty_value 0',
+    '#default_value' => 'one',
+    '#empty_value' => 0,
+  );
+  $form['empty_value_one'] = $base + array(
+    '#title' => '#default_value = #empty_value',
+    '#default_value' => 'one',
+    '#empty_value' => 'one',
+  );
+
+  $form['no_default'] = $base + array(
+    '#title' => 'No #default_value',
+  );
+  $form['no_default_optional'] = $base + array(
+    '#title' => 'No #default_value, not #required',
+    '#required' => FALSE,
+    '#description' => 'Should result in an empty string (default of #empty_value), because it is optional.',
+  );
+
+  $form['no_default_empty_option'] = $base + array(
+    '#title' => 'No #default_value, #empty_option',
+    '#empty_option' => '- Choose -',
+  );
+  $form['no_default_empty_option_optional'] = $base + array(
+    '#title' => 'No #default_value, not #required, #empty_option',
+    '#required' => FALSE,
+    '#empty_option' => '- Dismiss -',
+    '#description' => 'Should result in an empty string (default of #empty_value), because it is optional.',
+  );
+
+  $form['no_default_empty_value'] = $base + array(
+    '#title' => 'No #default_value, #empty_value 0',
+    '#empty_value' => 0,
+    '#description' => 'Should never result in 0.',
+  );
+  $form['no_default_empty_value_one'] = $base + array(
+    '#title' => 'No #default_value, #empty_value one',
+    '#empty_value' => 'one',
+    '#description' => 'A mistakenly assigned #empty_value contained in #options should not be valid.',
+  );
+  $form['no_default_empty_value_optional'] = $base + array(
+    '#title' => 'No #default_value, not #required, #empty_value 0',
+    '#required' => FALSE,
+    '#empty_value' => 0,
+    '#description' => 'Should result in 0, because it is optional.',
+  );
+
+  $form['multiple'] = $base + array(
+    '#title' => '#multiple, #default_value two',
+    '#default_value' => array('two'),
+    '#multiple' => TRUE,
+  );
+  $form['multiple_no_default'] = $base + array(
+    '#title' => '#multiple, no #default_value',
+    '#multiple' => TRUE,
+  );
+  $form['multiple_no_default_required'] = $base + array(
+    '#title' => '#multiple, #required, no #default_value',
+    '#required' => TRUE,
+    '#multiple' => TRUE,
+  );
+
+  $form['submit'] = array('#type' => 'submit', '#value' => 'Submit');
+  return $form;
+}
+
+/**
+ * Form submit handler for form_test_select().
+ */
+function form_test_select_submit($form, &$form_state) {
+  drupal_json_output($form_state['values']);
+  exit();
+}
+
+/**
  * Build a form to test disabled elements.
  */
 function _form_test_disabled_elements($form, &$form_state) {
diff --git a/modules/system/system.admin.inc b/modules/system/system.admin.inc
index ff70cc279..7b860c124 100644
--- a/modules/system/system.admin.inc
+++ b/modules/system/system.admin.inc
@@ -2941,7 +2941,7 @@ function system_actions_manage() {
   actions_synchronize();
   $actions = actions_list();
   $actions_map = actions_actions_map($actions);
-  $options = array(t('Choose an advanced action'));
+  $options = array();
   $unconfigurable = array();
 
   foreach ($actions_map as $key => $array) {
@@ -3013,9 +3013,7 @@ function system_actions_manage_form($form, &$form_state, $options = array()) {
   );
   $form['parent']['action'] = array(
     '#type' => 'select',
-    '#default_value' => '',
     '#options' => $options,
-    '#description' => '',
   );
   $form['parent']['actions'] = array('#type' => 'actions');
   $form['parent']['actions']['submit'] = array(
diff --git a/modules/system/system.module b/modules/system/system.module
index 865eec1f1..3e6954f06 100644
--- a/modules/system/system.module
+++ b/modules/system/system.module
@@ -399,9 +399,13 @@ function system_element_info() {
   );
   $types['select'] = array(
     '#input' => TRUE,
-    '#size' => 0,
+    // In order to be able to determine whether a select list needs an empty
+    // default option, #required has to be NULL by default, as form_builder()
+    // preemptively sets #required to FALSE for all elements.
+    // @see form_process_select()
+    '#required' => NULL,
     '#multiple' => FALSE,
-    '#process' => array('ajax_process_form'),
+    '#process' => array('form_process_select', 'ajax_process_form'),
     '#theme' => 'select',
     '#theme_wrappers' => array('form_element'),
   );
diff --git a/modules/trigger/trigger.admin.inc b/modules/trigger/trigger.admin.inc
index 33a3fc3f8..36e7cc715 100644
--- a/modules/trigger/trigger.admin.inc
+++ b/modules/trigger/trigger.admin.inc
@@ -177,7 +177,6 @@ function trigger_assign_form($form, $form_state, $module, $hook, $label) {
   );
   // List possible actions that may be assigned.
   if (count($options) != 0) {
-    array_unshift($options, t('Choose an action'));
     $form[$hook]['parent']['aid'] = array(
       '#type' => 'select',
       '#options' => $options,