view of unformatted list invalidating cache issues

Question

I have a view that shows the title of a single content type as an unformatted list. I have an argument for a nid-contextual filter that I pass to the view in

function modulename_views_pre_view($view, $display_id, array &$args) {
 ....
 $args[0] = $filter_value;
 }

The value for the contextual filter is a value the user can select and is set in \Drupal::service('user.private_tempstore'). Every time the user selects a different value from a select form element, the view should show different results. However, it caches the output and only if I clear all caches it shows the correct output. But if I format the view output as a table, then everything works totally fine and the new results are shown immediately.

The cache tags for this view are given as follows:

print_r($view->getCacheTags());
Array ( [0] => config:views.view.users_in_class [1] => node_list ) 

Do I have to specifically invalidate something here or am I missing something else ? I thought that the cache tag node_list would already be enough. And why are results being cached when having the format as an unformatted list?

Answer 1

The cache tag node_list only works for database changes in the node table, but this is not happening when the user selects a filter value.

This is from the point of the View a cache context. So if you don't find a way to configure the View to handle this correctly, you could assign a custom cache context for the filter value.

The whole picture, which the View can't know because you provide only the filter value to it, is a mix of tag and context. You would need a cache tag for the private tempstore and a context for the current user to get the caching right:

function modulename_views_pre_view($view, $display_id, array &$args) {
  ...
  $uid = \Drupal::currentUser()->id();
  $view->element['#cache']['tags'][] = 'users_in_class.' . $uid;
  $view->element['#cache']['contexts'][] = 'user';
}

and then invalidate the tag when changing the private tempstore of a user $uid:

Cache::invalidateTags(['users_in_class.' . $uid']);