How to fix error Undefined index: parent in taxonomy_form_term_submit()?

Question

I got below error on my site recently.

Notice: Undefined index: parent in taxonomy_form_term_submit() (line 829 of /var/www/Sites/xxxxx/modules/taxonomy/taxonomy.admin.inc).

I google it and find there is an old issue but seems nothing solved.

In the issue, @Cracu did mention some part of core code may cause this error:

  if (!variable_get('taxonomy_override_selector', FALSE)) {
    $parent = array_keys(taxonomy_get_parents($term->tid));
    $children = taxonomy_get_tree($vocabulary->vid, $term->tid);

    // A term can't be the child of itself, nor of its children.
    foreach ($children as $child) {
      $exclude[] = $child->tid;
    }
    $exclude[] = $term->tid;

    $tree = taxonomy_get_tree($vocabulary->vid);
    $options = array('<' . t('root') . '>');
    if (empty($parent)) {
      $parent = array(0);
    }
    foreach ($tree as $item) {
      if (!in_array($item->tid, $exclude)) {
        $options[$item->tid] = str_repeat('-', $item->depth) . $item->name;
      }
    }
    $form['relations']['parent'] = array(
      '#type' => 'select',
      '#title' => t('Parent terms'),
      '#options' => $options,
      '#default_value' => $parent,
      '#multiple' => TRUE,
    );

  }

I try to look into the latest core, this part of code is still there with same logics. Unfortunately, I need taxonomy_override_selector be TRUE.

Apart from setting taxonomy_override_selector to FALSE or adding new form validation handler to set $form_state['values']['parent'].

Do anyone know if there is solution for that?

Answer 1

There's a couple of ways you could go about the problem:

1. Patch Core: If there's no outstanding issue for the problem, alter core, create a patch & bug report, and submit your patch. You can manage your patch in your deployment process until the patch is accepted upstream.
2. Custom Module: Looking at the comment above the code you posted, it was authored with the intention that someone might need to alter the form ("Contrib modules can then intercept before hook_form_alter to provide scalable alternatives."). You can use a HOOK_form_taxonomy_form_term_alter invocation to alter the submission handler or the form array to mitigate the warning introduced.