ServiceProviderBase override "winner" - can this be done with module weight?

Question

It is noted that modules implementing ServiceProviderBase to alter defined services can 'lose' to other modules overriding the same service as there is no way to know which one should overtake in that situation.

Is this 'fixable' by making your modules weight higher than the others?

Answer 1

Yes, the serviceProviderClasses are discovered in DrupalKernel::discoverServiceProviders(), I've stopped the code there and the list was sorted by module weight and modules with the same weight alphabetically.

Answer 2

The answer by 4k4 is correct, I'd like to share some an additional note about changing the module weight...

If you add a module_set_weight() in a hook_install() it won't have any immediate effect on the order inside DrupalKernel::discoverServiceProviders() (as this would have already run during the install process). You will need to clear Drupal cache's first.

Here's the hook_install I'm using, with some code copied over from drupal_flush_all_caches() avoiding doing a second full cache clear in the same request.

/**
 * Implements hook_install().
 */
function mymodule_install() {
  module_set_weight('mymodule', 1);

  $module_handler = \Drupal::moduleHandler();
  $module_data = system_rebuild_module_data();
   // Rebuild and reboot a new kernel. A simple DrupalKernel reboot is not
  // sufficient, since the list of enabled modules might have been adjusted
  // above due to changed code.
  $files = [];
  foreach ($module_data as $name => $extension) {
    if ($extension->status) {
      $files[$name] = $extension;
    }
  }
  \Drupal::service('kernel')->updateModules($module_handler->getModuleList(), $files);

}