Non-Required Date Field Error

Webform does not support hiding the day. If you want to hide the day, you're going to have to write some more complicated javascript to include a day (e.g. 1) when month/year are present and not when it isn't.

Yes, you have some custom code. You'll need to find support for that outside the webform issue queue.

Wow. My error. I had forgotten that this feature went in.

I suggest you don't use hiding the day until this bug is addressed.

I have came across this issue as well.

It turns out that those are the lines that are responsible for the issue:

function webform_validate_date($element, $form_state) {
  if ($element['month']['#value'] !== '' || $element['day']['#value'] !== '' || $element['year']['#value'] !== '') {
    // Check that each part of the date has been filled in.
    foreach (array('day', 'month', 'year') as $field_type) {
      if (empty($element[$field_type]['#value'])) {
        form_error($element[$field_type], t('!part in !name is missing.', array('!name' => $element['#title'], '!part' => $element[$field_type]['#title'])));

Basically when the day / month field is hidden - it gets automatically set to 1. Therefore if we leave other fields empty (even for non-required field) the condition is met, inner block is executed and error set.

To prevent that I have added a check - the value for the date part is only checked if this part is not hidden / excluded.

function webform_validate_date($element, $form_state) {
  // An array of excluded elements.
  $excludes = isset($element['#exclude']) ? $element['#exclude'] : array();
  // Create a few variables as a shorthand for next checks.
  $day_exclude = in_array('day', $excludes);
  $month_exclude = in_array('month', $excludes);
  $year_exclude = in_array('year', $excludes);

  // We need to check the value for a given parte of the date only if the part
  // has not been excluded. If it has been excluded - the value is set to 1 and
  // will cause error of missing fields.
  if ((!$month_exclude && $element['month']['#value'] !== '') || (!$day_exclude && $element['day']['#value'] !== '') || (!$year_exclude && $element['year']['#value'] !== '')) {

that helped but caused php notices in submit function - so I have added a few issets to submit function as well:

function _webform_submit_date($component, $value) {
  // Convert the date to an ISO 8601 format.
  // Additional checks to prevent php notices.
  return (isset($value['year']) && $value['year'] && isset($value['month']) && $value['month'] && isset($value['day']) && $value['day']) ? webform_date_string($value, 'date') : '';
}

This worked for me.

Patch in #10 works for me

The patch in #10 works for me as well.

The patch #10 working fine for Webform 7.x-4.12.

The patch #10 works for me

I have applied this patch #10 and its working fine.

Thanks for the patch. Great work.

I simplified the test a bit and removed the safety checks for #required. Also, I don't get the PHP notices you mention. Please re-open if you do with an explanation. I don't see why/how the day/month/year should be missing from the value array. They should be present but empty.

Committed to 7.x-4.x.

Closing to clear out the old Webform 8.x-4.x branch. See #2827845: [roadmap] YAML Form 8.x-1.x to Webform 8.x-5.x.