Undefined index: time in scheduler_date_popup_pre_validate_alter()

Hello hgoto,
Thanks for the detailed explanation. However, it is strange that you have this error, because I do not get it. There must be something different between our drupal site setups. If I had seen this error before I would have corrected it! I have a few questions:

1. What php version are you using? I'm on 5.5.27
2. What type of date-picker are you using? see /admin/config/date/date_popup
3. When selecting a date, do you also have a time entry field which you leave blank?
4. What are the relative weights of your Scheduler and Date modules? Look in db table called system.

In my scheduler_date_popup_pre_validate_alter() I always get a 'time' value in the input array:

-- scheduler_date_popup_pre_validate_alter --
original $input: Array
(
    [date] => 26/04/2016
    [time] => 
)

$default_time: 1461604500
$input after setting default: Array
(
    [date] => 26/04/2016
    [time] => 18:15
)

If you want to try it, the above debug was created using:

/**
 * Implements hook_date_popup_pre_validate_alter().
 */
function scheduler_date_popup_pre_validate_alter($element, $form_state, &$input) {
  dd('-- scheduler_date_popup_pre_validate_alter --');
  dd($input, 'original $input');
  // Provide a default time if this is enabled and the time field is empty.
  if (variable_get('scheduler_allow_date_only', FALSE) && $element['#array_parents'][0] == 'scheduler_settings' && $input['date'] != '' && $input['time'] == '') {
    // Get the default time as a timestamp number.
    $default_time = strtotime(variable_get('scheduler_default_time', SCHEDULER_DEFAULT_TIME));
    dd($default_time, '$default_time');
    // Set the time in the required format just as if the user had typed it.
    $input['time'] = format_date($default_time, 'custom', variable_get('scheduler_time_only_format', SCHEDULER_TIME_ONLY_FORMAT));
    dd($input, '$input after setting default');
  }
  dd('-- scheduler_date_popup_pre_validate_alter -- END');
}

Yes, that's it. If the time part is removed then the $input array does not have 'time' key. Interestingly, the devel module backtrace has some fault in it, which means the warning was not being shown for me. When I removed the krumo backtrace display and reverted to 'standard drupal' the warning then showed up.

I will make this change. There is no corresponding fault in 8.x because currently we do not use the scheduler format for the date pop-up, and this conversion has not been decided yet.

I also took the opportunity to use !empty() on the date array key, as that is safer than testing for != ''

Thank you, hgoto.