Table form valueCallback strange behaviour

Question

I am creating a table form using the table element. I do not push sub elements into #rows. I work as with children elements. But valueCallback does not map values right. I am looking inside. It looks very strange. Especially:

return is_array($input) ? array_combine($input, $input) : [];

$input always is array. So combining result is weird with "array" key https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Render%21Element%21Table.php/function/Table%3A%3AvalueCallback/8.5.x

public static function valueCallback(&$element, $input, FormStateInterface $form_state) {

  // If #multiple is FALSE, the regular default value of radio buttons is used.
  if (!empty($element['#tableselect']) && !empty($element['#multiple'])) {

    // Contrary to #type 'checkboxes', the default value of checkboxes in a
    // table is built from the array keys (instead of array values) of the
    // #default_value property.
    // @todo D8: Remove this inconsistency.
    if ($input === FALSE) {
      $element += [
        '#default_value' => [],
      ];
      $value = array_keys(array_filter($element['#default_value']));
      return array_combine($value, $value);
    }
    else {
      return is_array($input) ? array_combine($input, $input) : [];
    }
  }
}

For me $input already is ready to move into #value. It does not need altering here. I hope it works well and I do something wrong. But not it seems weird for. Clarify it, please.

Answer 1

My solution is below. It is a weird solution because It requires small changes.

Define a table value callback.

    $form['links'] = [
      '#type' => 'table',
      ...
      '#value_callback' => array($this, 'valueCallback'),
    ];

Implement the callback.

 /**
   * {@inheritdoc}
   */
  public static function valueCallback(&$element, $input, FormStateInterface $form_state) {
    return $input;
  }

The data has structure as it has been sent. So the standard data processing works badly for my case.