How do I invalidate cache of an embedded view?

Question

I have a node type "Article" that contains a repeating Paragraphs field. One of the paragraph types let's the user embed a view using a entity reference field. When rendering an Article node containing a views reference I embed the selected view in hook_preprocess_paragraph like this:

$view_id = $paragraph->field_view->target_id;
$view = \Drupal\views\Views::getView($view_id);
$view->setDisplay('embed_1');
$vars['content'] = $view->preview();

This is working fine except when I enable caching. For example one of my views lists nodes of the type "Event". When I add a new Event it does not show up in the listing until I clean the cache. I could force clean the cache when inserting / updating / deleting an "Event" but I would much rather use Drupal 8's cache tag system and only invalidate the cached content that contains event lists. The problem is I cannot get it to work.

So far I have tried adding cache tags to the node, the view, and the paragraph in hook_preprocess_paragraph and hook_preprocess_node like this:

$vars['paragraph']->addCacheTags(['node_list']);
...
$view->storage->addCacheTags(['node_list']);
...
$vars['node']->addCacheTags(['node_list']);

According to this page node_list can be used for node listings to invalidate the cache whenever a node is updated. But it has no effect. Maybe the preprocess hooks are to late to add cache tags?

What am I missing?

Edit:

After some more testing I found that if I edit an event, the changes can be seen in the listing and if I remove an event it disappears from the listing. The problem only occurs when adding new events.

Answer 1

Try to use buildRenderable(), that should ensure that the necessary cacheability metadata is added automatically.

$vars['content'] = $view->buildRenderable();

Hint: You might be interested in my Views Custom Cache Tag project. The node_list cache tag is invalidated every time any type of node is saved, even though your view only changes when an event changes. Using that module and a bit of custom code as shown on the project page, you have fewer cache invalidations and better performance.

Answer 2

Add the cache tag to the render array, not the object:

$vars['#cache']['tags'][] = 'node_list';

In preprocess you are working with render arrays, not objects. Look at this page of the documentation: https://www.drupal.org/developing/api/8/render/arrays/cacheability

Answer 3

I solved a similar issue using the module Views Custom Cache Tag:

In the view editor, under Advanced, click on Cache, then select "Custom tag based". To have the view rerendered each time a node is changed, enter 'node_list' in the custom tag settings.