Index: includes/form.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/form.inc,v
retrieving revision 1.494
diff -u -p -r1.494 form.inc
--- includes/form.inc	22 Sep 2010 03:34:57 -0000	1.494
+++ includes/form.inc	24 Sep 2010 15:32:15 -0000
@@ -1189,7 +1189,15 @@ function _form_validate(&$elements, &$fo
     // 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'])));
+      $t_args = array(
+        '!title' => $elements['#title'],
+      );
+      if (!empty($elements['#required_message'])) {
+        form_error($elements, $t($elements['#required_message'], $t_args));
+      }
+      else {
+        form_error($elements, $t('!title field is required.', $t_args));
+      }
     }
 
     // Call user-defined form level validators.
@@ -1813,7 +1821,7 @@ function _form_builder_handle_input_elem
       // Avoid image buttons (which come with garbage value), so we only get value
       // for the button actually clicked.
       if (!isset($element['#value']) && empty($element['#has_garbage_value'])) {
-        $element['#value'] = isset($element['#default_value']) ? $element['#default_value'] : '';
+        $element['#value'] = array_key_exists('#default_value', $element) ? $element['#default_value'] : '';
       }
     }
   }
Index: modules/field/tests/field.test
===================================================================
RCS file: /cvs/drupal/drupal/modules/field/tests/field.test,v
retrieving revision 1.41
diff -u -p -r1.41 field.test
--- modules/field/tests/field.test	24 Sep 2010 00:37:42 -0000	1.41
+++ modules/field/tests/field.test	24 Sep 2010 15:32:58 -0000
@@ -1300,7 +1300,7 @@ class FieldFormTestCase extends FieldTes
     // Submit with missing required value.
     $edit = array();
     $this->drupalPost('test-entity/add/test-bundle', $edit, t('Save'));
-    $this->assertRaw(t('!name field is required.', array('!name' => $this->instance['label'])), 'Required field with no value fails validation');
+    $this->assertRaw(t('!title field is required.', array('!title' => $this->instance['label'])), 'Required field with no value fails validation');
 
     // Create an entity
     $value = mt_rand(1, 127);
@@ -1316,7 +1316,7 @@ class FieldFormTestCase extends FieldTes
     $value = '';
     $edit = array("{$this->field_name}[$langcode][0][value]" => $value);
     $this->drupalPost('test-entity/manage/' . $id . '/edit', $edit, t('Save'));
-    $this->assertRaw(t('!name field is required.', array('!name' => $this->instance['label'])), 'Required field with no value fails validation');
+    $this->assertRaw(t('!title field is required.', array('!title' => $this->instance['label'])), 'Required field with no value fails validation');
   }
 
 //  function testFieldFormMultiple() {
Index: modules/file/file.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/file/file.module,v
retrieving revision 1.40
diff -u -p -r1.40 file.module
--- modules/file/file.module	13 Sep 2010 01:09:25 -0000	1.40
+++ modules/file/file.module	24 Sep 2010 15:32:15 -0000
@@ -557,7 +557,7 @@ function file_managed_file_validate(&$el
 
   // Check required property based on the FID.
   if ($element['#required'] && empty($element['fid']['#value']) && !in_array($clicked_button, array('upload_button', 'remove_button'))) {
-    form_error($element['upload'], t('!name field is required.', array('!name' => $element['#title'])));
+    form_error($element['upload'], t('!title field is required.', array('!title' => $element['#title'])));
   }
 
   // Consolidate the array value of this field to a single FID.
Index: modules/simpletest/tests/form.test
===================================================================
RCS file: /cvs/drupal/drupal/modules/simpletest/tests/form.test,v
retrieving revision 1.67
diff -u -p -r1.67 form.test
--- modules/simpletest/tests/form.test	19 Sep 2010 18:39:18 -0000	1.67
+++ modules/simpletest/tests/form.test	24 Sep 2010 15:32:15 -0000
@@ -123,6 +123,22 @@ class FormsTestCase extends DrupalWebTes
   }
 
   /**
+   * Tests #required with custom validation errors.
+   *
+   * @see form_test_validate_required_form()
+   */
+  function testRequiredValidation() {
+    $this->drupalPost('form-test/validate-required', array(), 'Submit');
+
+    // Verify that the #required error message can be overridden.
+    foreach (array('Textfield', 'Textarea', 'Checkboxes', 'Radios') as $title) {
+      $this->assertNoText(t('!title field is required.', array('!title' => $title)));
+      $this->assertText(strtr('Yo, ur !title iz amptee!', array('!title' => $title)));
+    }
+    $this->assertNoText(t('An illegal choice has been detected. Please contact the site administrator.'));
+  }
+
+  /**
    * Test default value handling for checkboxes.
    *
    * @see _form_test_checkbox()
@@ -131,7 +147,7 @@ class FormsTestCase extends DrupalWebTes
     // First, try to submit without the required checkbox.
     $edit = array();
     $this->drupalPost('form-test/checkbox', $edit, t('Submit'));
-    $this->assertRaw(t('!name field is required.', array('!name' => 'required_checkbox')), t('A required checkbox is actually mandatory'));
+    $this->assertRaw(t('!title field is required.', array('!title' => 'required_checkbox')), t('A required checkbox is actually mandatory'));
 
     // Now try to submit the form correctly.
     $values = drupal_json_decode($this->drupalPost(NULL, array('required_checkbox' => 1), t('Submit')));
@@ -404,7 +420,7 @@ class FormValidationTestCase extends Dru
     // ensure that the title field is not validated, but the #element_validate
     // handler for the 'test' field is triggered.
     $this->drupalPost($path, $edit, t('Partial validate'));
-    $this->assertNoText(t('!name field is required.', array('!name' => 'Title')));
+    $this->assertNoText(t('!title field is required.', array('!title' => 'Title')));
     $this->assertText('Test element is invalid');
 
     // Ensure not validated values are not available to submit handlers.
@@ -414,7 +430,7 @@ class FormValidationTestCase extends Dru
     // Now test full form validation and ensure that the #element_validate
     // handler is still triggered.
     $this->drupalPost($path, $edit, t('Full validate'));
-    $this->assertText(t('!name field is required.', array('!name' => 'Title')));
+    $this->assertText(t('!title field is required.', array('!title' => 'Title')));
     $this->assertText('Test element is invalid');
   }
 }
@@ -837,7 +853,7 @@ class FormsFormStorageTestCase extends D
 
       // Test it again, but first trigger a validation error, then test.
       $this->drupalPost('form-test/state-persist', array('title' => ''), t('Submit'), $options);
-      $this->assertText(t('!name field is required.', array('!name' => 'title')));
+      $this->assertText(t('!title field is required.', array('!title' => 'title')));
       // Submit the form again triggering no validation error.
       $this->drupalPost(NULL, array('title' => 'foo'), t('Submit'), $options);
       $this->assertText('State persisted.');
Index: modules/simpletest/tests/form_test.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/simpletest/tests/form_test.module,v
retrieving revision 1.48
diff -u -p -r1.48 form_test.module
--- modules/simpletest/tests/form_test.module	27 Aug 2010 11:54:32 -0000	1.48
+++ modules/simpletest/tests/form_test.module	24 Sep 2010 15:32:15 -0000
@@ -24,6 +24,12 @@ function form_test_menu() {
     'access arguments' => array('access content'),
     'type' => MENU_CALLBACK,
   );
+  $items['form-test/validate-required'] = array(
+    'title' => 'Form #required validation',
+    'page callback' => 'drupal_get_form',
+    'page arguments' => array('form_test_validate_required_form'),
+    'access arguments' => array('access content'),
+  );
   $items['form-test/limit-validation-errors'] = array(
     'title' => 'Form validation with some error suppression',
     'page callback' => 'drupal_get_form',
@@ -298,6 +304,46 @@ function form_test_validate_form_validat
 }
 
 /**
+ * Form constructor for testing #required and custom form errors.
+ */
+function form_test_validate_required_form($form, &$form_state) {
+  $form['textfield'] = array(
+    '#type' => 'textfield',
+    '#title' => 'Textfield',
+    '#required' => TRUE,
+    '#required_message' => 'Yo, ur !title iz amptee!',
+  );
+  $form['textarea'] = array(
+    '#type' => 'textarea',
+    '#title' => 'Textarea',
+    '#required' => TRUE,
+    '#required_message' => 'Yo, ur !title iz amptee!',
+  );
+  $form['checkboxes'] = array(
+    '#type' => 'checkboxes',
+    '#title' => 'Checkboxes',
+    '#options' => array(
+      'option1' => 'Option1',
+      'option2' => 'Option2',
+    ),
+    '#required' => TRUE,
+    '#required_message' => 'Yo, ur !title iz amptee!',
+  );
+  $form['radios'] = array(
+    '#type' => 'radios',
+    '#title' => 'Radios',
+    '#options' => array(
+      'option1' => 'Option1',
+      'option2' => 'Option2',
+    ),
+    '#required' => TRUE,
+    '#required_message' => 'Yo, ur !title iz amptee!',
+  );
+  $form['submit'] = array('#type' => 'submit', '#value' => 'Submit');
+  return $form;
+}
+
+/**
  * Builds a simple form with a button triggering partial validation.
  */
 function form_test_limit_validation_errors_form($form, &$form_state) {
Index: modules/system/system.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.module,v
retrieving revision 1.963
diff -u -p -r1.963 system.module
--- modules/system/system.module	24 Sep 2010 00:37:44 -0000	1.963
+++ modules/system/system.module	24 Sep 2010 15:32:15 -0000
@@ -371,6 +371,11 @@ function system_element_info() {
   );
   $types['radios'] = array(
     '#input' => TRUE,
+    // If no #default_value is specified and a user agent submits no value for
+    // #type 'radios', then _form_builder_handle_input_element() would assign an
+    // empty string as #value, which in turn would trigger an "illegal choice"
+    // error in _form_validate().
+    '#default_value' => NULL,
     '#process' => array('form_process_radios'),
     '#theme_wrappers' => array('radios'),
     '#pre_render' => array('form_pre_render_conditional_form_element'),