drupal field widget not saving submitted data - drupal

Question

I'm trying to create a custom widget but when I submit, Drupal doesn't seem to save any data. When using hook_field_attach_submit() to display what data I've pasted, it is listed as null.
Strangely, if i change the #type to be a single textfield instead of a fieldset it will save only the first character of the string that has been entered.
This seems like a validation issue, but I'm not sure how to hook into it or to debug the problem. Where can I go from here?
<?php
function guide_field_widget_info(){
dpm("guide_field_widget_info");
return array(
'guide_text_textfield' => array(
'label' => t('test Text field'),
'field types' => array('text'),
'settings' => array('size' => 60),
'behaviors' => array(
'multiple values' => FIELD_BEHAVIOR_CUSTOM,
'default value' => FIELD_BEHAVIOR_DEFAULT,
),
)
);
}
function guide_field_widget_form(&$form, &$form_state, $field, $instance, $langcode, $items, $delta, $element) {
$field_name = $instance['field_name'];
$required = $element['#required'];
$item =& $items[$delta];
$element += array(
'#type' => 'fieldset',
'#title' => t('helloooooooo'),
);
$required = $element['#required'];
$item =& $items[$delta];
$element['nametest'] = array(
'#title' => t('Name'),
'#type' => 'textfield',
'#required' => $required,
// use #default_value to prepopulate the element
// with the current saved value
'#default_value' => isset($item['nametest']) ? $item['nametest'] : '',
);
$element['checkme'] = array(
'#title' => t('Check this box or dont'),
'#type' => 'checkbox',
'#default_value' => isset($item['checkme']) ? $item['checkme'] : '',
);
//When changing the above code to have a single field, $value is no longer null but will display the first character of the string. I've pasted the code I used to test beloe
/*
$element+= array(
'#title' => t('Name'),
'#type' => 'textfield',
'#default_value' => isset($item['nametest']) ? $item['nametest'] : '',
);
*/
return $element;
}
//hooking this here is required given that after submit, the value is a multidimensional array, whereas the expected value of text is, well, text :-)
function guide_field_attach_submit($entity_type, $entity, $form, &$form_state){
dpm($form,"guide_field_attach_submit data"); //shows $form[field_test_field][und][0] [value] as being null
}

Answer 1

hook_field_is_empty is mandatory and has to be implement like following:
/**
* Implements hook_field_is_empty().
*/
function MODULENAME_field_is_empty($item, $field) {
if ($field['type'] == 'FIELDTYPE') {
if (empty($item[$field['type']]['YourField']) ) {
return (TRUE);
}
}
return (FALSE);
}