Can't add a custom filter criteria

Question

I try to add a new filter criteria to my views with a custom module.

I manage to display my new filter on the filter criteria list but when I select it and go to "Add and configure filter criteria" I have an error saying:

The handler for this item is broken or missing. The following details are available:

Enabling the appropriate module may solve this issue. Otherwise, check to see if there is a module update available.

Here is my content_search.module :

function content_search_views_data_alter(&$data)
{
    $data['node']['content_search_filter'] = [
        'title' => t('Content search filter'),
        'filter' => [
            'title' => t('Content search filter'),
            'help' => 'Filters nodes on its content',
            'field' => 'nid',
            'id' => 'content_search_filter',
        ]
    ];
}

And here is my ContentSearchFilterPlugin, placed in content_search/src/Plugin/Filter/ContentSearchFilterPlugin.php

namespace Drupal\content_search\Plugin\Filter;

use Drupal\views\ViewExecutable;
use Drupal\views\Plugin\views\display\DisplayPluginBase;
use Drupal\views\Plugin\views\filter\FilterPluginBase;

/**
 * Filters nodes on on their content
 *
 * @ingroup views_filter_handlers
 *
 * @ViewsFilter("content_search_filter")
 */
class ContentSearchFilterPlugin extends FilterPluginBase {
  /**
   * {@inheritdoc}
   */
  public function init(ViewExecutable $view, DisplayPluginBase $display, array &$options = NULL) {
    parent::init($view, $display, $options);
    $this->valueTitle = t('Content search filter');
  }


  public function query() {
    parent::query();
    // TODO: custom query here
  }

}

What am I missing ?

Answer 1

I think you have a problem with plugin file organization. It should be :

content_search/src/Plugin/views/filter/ContentSearchFilterPlugin.php

...instead of

content_search/src/Plugin/Filter/ContentSearchFilterPlugin.php

And the namespace for this file should be

namespace Drupal\content_search\Plugin\views\filter;

Answer 2

This works for me in Drupal8:

Name of custom module: custom_modulename

Name of table in SQL: name_of_sql_table

Selecting the ID for filtering

function custom_modulename_views_data_alter(array &$data) { 
  $data['name_of_sql_table']['custom_modulename'] = [
    'title' => t('Title shown'),
    'group' => t('abc'),
    'filter' => [
      'title' => t('Filter'),
      'help' => t('Self made'),
      'field' => 'id',
      'id' => 'string'
    ],
  ];
}

Hint: If you want to use options etc. then it is much more complicated. Use a Class for that.