How do I programmatically set the default value of an exposed filter?

Question

I seen many answers for Drupal 7, but I can't find any information for Drupal 9.

In hook_form_alter(), $form['field_assigned_location_target_id']['#default_value'] = '553'; doesn't alter the default value for an exposed filter, which uses the value in the settings.

$form['field_assigned_location_target_id']['#value'] = '553'; changes the value initially displayed on the filter, but it's the value submitted from the exposed filter form, independently from the value the users want to submit.

Answer 1

I know the question is old, but hopefully this will help someone else. After working extensively to use hook_views_pre_view, I finally found the solution by switching to hook_views_pre_build. This code allowed me to make the changes I needed.

/**
 * Implements hook_views_pre_build().
 */
function  msul_newsletter_helper_views_pre_build(Drupal\views\ViewExecutable $view){
  /*
   * to check the format of the argument for setExposedInput, view the results
   * of getExposedInput on your view WHICH HAS HAD EXPOSED FILTERS SUBMITTED.
   * I use dpm($view->getExposedInput());
   */

  //always check the view ID so you don't affect all views.
  if($view->id()=='newsletter'){
    //check display id if you don't want to affect all displays in view.
    if( $view->current_display == 'page_2') {
      if(empty($view->getExposedInput())){
        //in my case I get $editionList from a database query.

        // because I am putting this as a default, I don't worry about other input,
        // but if you are concerned about other input, modify the array
        // from $view->getExposedInput() instead of just placing the information. 
        $view->setExposedInput(['newsletter_edition_public_filter'=>
            ['edition'=>$editionList]
        ]);
      }
    }

    //in this case, I affect 2 displays.
    if($view->current_display == 'page_4'
        || $view->current_display == 'block_1'
      ){
      if(empty($view->getExposedInput())){
        //in my case I get $latestEdition from a database query.
        $view->setExposedInput(['edition'=>['edition'=>[$latestEdition]]]);
      }
    }
  }
}