Error when date field is left blank

Indeed.
System also generates the error "Error message: This value should be of the correct primitive type."

The catching is done in OfficeHoursBaseSlot~validateOfficeHoursSlot()
Perhaps adding an override in OfficeHoursExceptionsSlot for this field.

Please note that the data should have been properly formatted in valueCallback() function.
(Please use today's dev-version, as I refactored stuff to adheere better to implementation pattern - see recent 2 issues.)

@johnv, This seems to be a kind of validation. Whenever we submit any forms, if we remains any fields empty, the whole field (*required) throws an error message on every element on the form. This might be system behavior for showing all fields required.

Using today's dev version and when saving the office hours field throws error as follows:

TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, class Drupal\office_hours\Element\OfficeHoursDatelist does not have a method "processOfficeHoursSlot" in call_user_func_array() (line 1010 of /var/www/html/web/core/lib/Drupal/Core/Form/FormBuilder.php)
#0 /var/www/html/web/core/lib/Drupal/Core/Form/FormBuilder.php(1010): call_user_func_array(Array, Array)
#1 /var/www/html/web/core/lib/Drupal/Core/Form/FormBuilder.php(1073): Drupal\Core\Form\FormBuilder->doBuildForm('field_config_ed...', Array, Object(Drupal\Core\Form\FormState))
#2 /var/www/html/web/core/lib/Drupal/Core/Form/FormBuilder.php(1073): Drupal\Core\Form\FormBuilder->doBuildForm('field_config_ed...', Array, Object(Drupal\Core\Form\FormState))
#3 /var/www/html/web/core/lib/Drupal/Core/Form/FormBuilder.php(1073): Drupal\Core\Form\FormBuilder->doBuildForm('field_config_ed...', Array, Object(Drupal\Core\Form\FormState))
#4 /var/www/html/web/core/lib/Drupal/Core/Form/FormBuilder.php(1073): Drupal\Core\Form\FormBuilder->doBuildForm('field_config_ed...', Array, Object(Drupal\Core\Form\FormState))
#5 /var/www/html/web/core/lib/Drupal/Core/Form/FormBuilder.php(1073): Drupal\Core\Form\FormBuilder->doBuildForm('field_config_ed...', Array, Object(Drupal\Core\Form\FormState))
#6 /var/www/html/web/core/lib/Drupal/Core/Form/FormBuilder.php(577): Drupal\Core\Form\FormBuilder->doBuildForm('field_config_ed...', Array, Object(Drupal\Core\Form\FormState))
#7 /var/www/html/web/core/lib/Drupal/Core/Form/FormBuilder.php(323): Drupal\Core\Form\FormBuilder->processForm('field_config_ed...', Array, Object(Drupal\Core\Form\FormState))
#8 /var/www/html/web/core/lib/Drupal/Core/Controller/FormController.php(73): Drupal\Core\Form\FormBuilder->buildForm(Object(Drupal\field_ui\Form\FieldConfigEditForm), Object(Drupal\Core\Form\FormState))
#9 [internal function]: Drupal\Core\Controller\FormController->getContentResult(Object(Symfony\Component\HttpFoundation\Request), Object(Drupal\Core\Routing\RouteMatch))
#10 /var/www/html/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array(Array, Array)
#11 /var/www/html/web/core/lib/Drupal/Core/Render/Renderer.php(580): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#12 /var/www/html/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(124): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure))
#13 /var/www/html/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array)
#14 /var/www/html/vendor/symfony/http-kernel/HttpKernel.php(169): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#15 /var/www/html/vendor/symfony/http-kernel/HttpKernel.php(81): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1)
#16 /var/www/html/web/core/lib/Drupal/Core/StackMiddleware/Session.php(58): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#17 /var/www/html/web/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(48): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#18 /var/www/html/web/core/modules/page_cache/src/StackMiddleware/PageCache.php(106): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#19 /var/www/html/web/core/modules/page_cache/src/StackMiddleware/PageCache.php(85): Drupal\page_cache\StackMiddleware\PageCache->pass(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#20 /var/www/html/web/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(48): Drupal\page_cache\StackMiddleware\PageCache->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#21 /var/www/html/web/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(51): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#22 /var/www/html/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#23 /var/www/html/web/core/lib/Drupal/Core/DrupalKernel.php(713): Stack\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#24 /var/www/html/web/index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request))
#25 {main}

@johnv just FYI

I cleared the cache and resubmitted the form and it saved now!
FYI i upgraded from ("^1.7") to today's dev version("1.x-dev@dev") directly.

on comment #2
I think the error is throwing from the core, due to a formatting.when doing OfficeHoursItem::formatValue for excempted values.
This is mentioned in "src/Plugin/Field/FieldType/OfficeHoursItem.php" itself #226
// Cast the time to integer, to avoid core's error
// "This value should be of the correct primitive type."

I think a casting needed for empty values in the exempted slots

Thanks,
I was working on this while you were commenting. Please check the new code.
The problem also occurred on the 'normal' basic list widget.

A problem with empty records.

There is an error in the naming of a class. a small character is used, instead of a capital character, resulting in 🐛 WSOD for OfficeHoursExceptionsSlot since update to 8.x-1.8+dev Fixed

Automatically closed - issue fixed for 2 weeks with no activity.