Facets do not display after page refresh

This sounds like a caching issue, I've tagged it as such and I'll have a look at how to reproduce it. Do you have page cache / dynamic page cache enabled?

I've reinstalled drupal, search API and facets and I can't reproduce this.

The problem was in the returning type. The function \Drupal\search_api\Query\ResultsCacheInterface::getResults() must return "The results with the given search ID, if present; NULL otherwise.". But in \Drupal\facets\Plugin\Block\FacetBlock::getCacheMaxAge() we returned 0, so it was the mistake. Attached patch fixed this.

getCacheMaxAge has nothing to do with the results. This sets the cacheability max age, see Drupal\Core\Cache\CacheableDependencyInterface

I think that cache of views module is a main cause. From ViewExecutable::execute()

    if ($cache->cacheGet('results')) {
      if ($this->pager->usePager()) {
        $this->pager->total_items = $this->total_rows;
        $this->pager->updatePageInfo();
      }
    }
    else {
      $this->query->execute($this);
      // Enforce the array key rule as documented in
      // views_plugin_query::execute().
      $this->result = array_values($this->result);
      $this->_postExecute();
      $cache->cacheSet('results');
    }

So, SearchApiQuery::execute() won't be executed, if $cache->cacheGet('results') returns some data. As a result hook_search_api_query_alter() won't be executed and facets won't be displayed. Probably, it should be fixed in a search_api module?

Hi! I think that I found the solve. It's a mistake in view's settings.
So, go to your_view - Edit - advanced - caching and choose there "Search API specific"

So "search api specific" or no caching should be the same thing, search api doesn't cache anything either (they also have max-age: 0). We have some code that disables views caches when saving a facet. http://cgit.drupalcode.org/facets/tree/src/Form/FacetForm.php#n325

Maybe we should look into disabling other cacheing abilities when facets are enabled on a view?

@bryanmanalo: you should first read up on the reason why we decided to disable cacheing for facets: http://cgit.drupalcode.org/facets/tree/src/Plugin/Block/FacetBlock.php?i...

The relevant snippet from that documentation is:

Search API gets those search results from a data source that can be external to Drupal. Therefore it is impossible to guarantee that the search results are in sync with the data managed by Drupal.

Facets won't work on a cached view for the foreseeable future, supporting that would be an absolute nightmare for the reason mentioned in there. What should happen in this issue is document that more clearly in the UI and/or readme file. If possible we should try to make sure that the cacheability options for the view are limited so people won't accidently disable the cacheing options.

@borisson_ : You are right about "search api specific" and "none" caching settings. They are the same. But when we create view by default cache specified as "Tag based".

@OlgaRabodzei: as mentioned in #13, facets has code that should set the view's cacheability to "none". If that doesn't work anymore, we should figure out why not and fix that code (and possibly add a test for it as well)

about d7: https://www.drupal.org/node/1612708

Regarding current issue: we should set current display for a cache option ('default' is used by default), before facet will be saved. Otherwise, we should use this:

- $display = &$view->storage->getDisplay($display);
+ $display = &$view->storage->getDisplay('default');

But we don't want change a cache type for all view. So, we should set a display before changing the options. I have attached a patch for review. It should help:)

I added a note in the readme.txt, which we need.

I also added a hook to remind people to disable views cacheing when saving a view that uses search api.
I think this is too invasive personally but let me know if y'all think this is better?

As for me this is unnecessary and note in the readme.txt will be enough.

In addition: does it mean that we should remove ability to change cache type? I mean this: http://cgit.drupalcode.org/facets/tree/src/Form/FacetForm.php#n325
The message looks like that we should change cache type manually.

Also, I'm not sure about all displays (see attached file). Probably, current display will be enough for this?
However, as I mentioned above, note in the readme.txt will be enough on my mind.

So, I think this should be enough information in the readme.

RTBC :)

Committed, thanks to everyone for the help!

Well, I'm not satisfied with the idea that facets cannot be procesed on top of a cached view. I think we should support that. I have no glue how, given the actual architecture.