Using Form API #states to set visibility of other fields based on term, using machine name

It is not hard to use the provided taxonomy_machine_name_term_load() function to do this; but the module page documentation should add the modern Drupal section (the function name has been corrected since D7).

    foreach ($search_fields as $key => $field) {
        $zip_term = taxonomy_machine_name_term_load('zip_code', 'search_by');
        if ($field === 'field_search_zip' || $field === 'field_search_radius') {
          $form[$field]['#states'] = [
            'visible' => [
              ':input[name="field_search_by"]' => ['value' => $zip_term->id()],
            ],
          ];
        }
        $county_term = taxonomy_machine_name_term_load('county', 'search_by');
        if ($field === 'field_address_county') {
          $form[$field]['#states'] = [
            'visible' => [
              ':input[name="field_search_by"]' => ['value' => $county_term->id()],
            ],
          ];
        }
      }

(this is looping

This is very silly, but made a helper module to do this: Taxonomy Machine Name Helper →

Now my code (note as before it loops through fields, which is a little unusual for this but doesn't change how this helper function is used really) looks like this:

        if ($field === 'field_search_zip' || $field === 'field_search_radius') {
          taxonomy_machine_name_helper_set_dependent_field_state($form, 'field_search_by', 'zip_code', 'search_by', $field);
        }
        elseif ($field === 'field_address_county') {
          taxonomy_machine_name_helper_set_dependent_field_state($form, 'field_search_by', 'county', 'search_by', $field);
        }

The signature of the function being used there is:

/**
 * Set form field state based on term machine name in controlling field.
 *
 * @param array $form
 *   Form to make the changes to.
 * @param string $controlling_field
 *   Machine name for the controlling field (must have options that are taxonomy terms).
 * @param string $term_machine_name
 *   Term machine name that triggers target field behavior (must be provided by Taxonomy Machine Name module).
 * @param string $target_field
 *   Machine name for the target field.
 * @param string $state
 *   Optional state to put the target field in when the term matching the term machine name is selected. Defaults to 'visible'.
 */
function taxonomy_machine_name_helper_set_dependent_field_state(&$form, $controlling_field, $term_machine_name, $vocabulary, $target_field, $state = 'visible')

It also checks that it can load a term of the given machine name, and logs a warning rather than blowing anything up if it cannot, and abstracting that code for re-use is really what tipped me into making it a contribution.

I made a separate module because i didn't really see this being accepted as a feature request but would happily roll it into taxonomy_machine_name itself if it is welcome.