Issue #2034991 by derhasi: Fixed Required modules may never be disabled by master.

 *   Array of module machine names of the master modules.

 *

 * @return array

 *   Array of module names required by the master modules. The list does not

 *   contain the master modules themselves.

 *   Array of module names required by the master modules or defined as required

 *   in the module info (as for core modules like field or user). The list does

 *   not contain the master modules themselves.

 */

function master_get_required_modules($master_modules) {

  // iterate over the whole module list.

  foreach ($module_data as $module => $data) {

    // If this is a master module, we skip it.

    if (!in_array($module, $master_modules) && !empty($data->required_by)) {

    if (in_array($module, $master_modules)) {

      // Do nothing.

    }

    // If the module is required via the module info, we do not ignore that and

    // add it to the list.

    elseif (!empty($data->info['required'])) {

      $required_modules[] = $module;

    }

    // If one or more master modules require this module, we add it to the list.

    elseif (!empty($data->required_by)) {

      $intersect = array_intersect_key($data->required_by, $master_keys);

      // If one or more master module require this module, we add it to the list.

      if (count($intersect) > 0) {

        $required_modules[] = $module;

      }