Issue #1998266: Add 'Exception day' feature - code style, add error message

- 'allowed hours' restrictions;

- input validation;

- use of either a 24 or 12 hour clock;

- (as per v8.x-1.7) an ability to add 'Exception days' with calendar date instead of weekday.

The formatter provides o.a.:

- a 'Current status' indicator ('open now'/'closed now');

- options to show all/none/open/current days;

- options to group days (E.g., "Mon-Fri 12:00-22:00");

- customizable element separators to display the 'office hours' any way you want. (See below for details.)

- (as per v8.x-1.7) an ability to determine the 'Exception days' to display in the future.

You can configure the formatter as follows:

- Add the field to an entity/node;

    return $elements;

  }

  // If field settings for this view_mode are not set, yet.

  if (!isset($settings['exceptions']['title'])) {

    \Drupal::messenger()->addMessage(

      t("Please review the display settings

        for field %field_name in view mode %view_mode, and save them again.", [

        '%field_name' => $field_name,

        '%view_mode' => $view_mode]));

    return $elements;

  }

  // Loop over formatters: $elements contains table/status/schema formatter.

  $label = $settings['exceptions']['title'] ?? '';

  foreach ($elements as $key => &$element) if (is_numeric($key)) {

    // If there is an exception, add an extra row to label the exceptions.

    // Note: may be changed in template_preprocess_office_hours_table().

    $label = $settings['exceptions']['title'];

    $exception_header = [];

    switch ($element['content']['#theme']) {

    /*

    // Find timezone fields, to be used in 'Current status'-option.

    $fields = field_info_instances( (isset($form['#entity_type']) ? $form['#entity_type'] : NULL), (isset($form['#bundle']) ? $form['#bundle'] : NULL));

    $fields = field_info_instances( (isset($form['#entity_type'])

      ? $form['#entity_type']

      : NULL), (isset($form['#bundle']) ? $form['#bundle'] : NULL));

    $timezone_fields = [];

    foreach ($fields as $field_name => $timezone_instance) {

      if ($field_name == $field['field_name']) {

      $timezone_field = field_read_field($field_name);

      if (in_array($timezone_field['type'], ['tzfield'])) {

        $timezone_fields[$timezone_instance['field_name']] = $timezone_instance['label'] . ' (' . $timezone_instance['field_name'] . ')';

        $timezone_fields[$timezone_instance['field_name']]

        = $timezone_instance['label']

        . ' ('

        . $timezone_instance['field_name'] . ')';

      }

    }

    if ($timezone_fields) {

namespace Drupal\office_hours\Plugin\Field\FieldType;

use Drupal\Core\Field\FieldDefinitionInterface;

use Drupal\Core\Field\FieldStorageDefinitionInterface;

use Drupal\office_hours\Plugin\Field\FieldType\OfficeHoursItem;

/**

 * Plugin implementation of the 'office_hours' field type.