src/Plugin/Block/FacetBlockDeriver.php

+<?php
+
+/**
+ * @file
+ * Contains Drupal\facets\Plugin\Block\FacetBlockDeriver.
+ */
+
+namespace Drupal\facets\Plugin\Block;
+
+use Drupal\Component\Plugin\PluginBase;
+use Drupal\Core\Plugin\Discovery\ContainerDeriverInterface;
+use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * This deriver creates a block for every facet that has been created.
+ */
+class FacetBlockDeriver implements ContainerDeriverInterface {
+
+  use StringTranslationTrait;
+
+  /**
+   * List of derivative definitions.
+   *
+   * @var array
+   */
+  protected $derivatives = [];
+
+  /**
+   * The entity storage used for facets.
+   *
+   * @var \Drupal\Core\Entity\EntityStorageInterface $facetStorage
+   */
+  protected $facetStorage;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, $base_plugin_id) {
+    $deriver = new static($container, $base_plugin_id);
+    $deriver->facetStorage = $container->get('entity_type.manager')->getStorage('facets_facet');
+
+    return $deriver;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDerivativeDefinition($derivative_id, $base_plugin_definition) {
+    $derivatives = $this->getDerivativeDefinitions($base_plugin_definition);
+    return isset($derivatives[$derivative_id]) ? $derivatives[$derivative_id] : NULL;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getDerivativeDefinitions($base_plugin_definition) {
+    $base_plugin_id = $base_plugin_definition['id'];
+
+    if (!isset($this->derivatives[$base_plugin_id])) {
+      $plugin_derivatives = [];
+
+      /** @var \Drupal\facets\FacetInterface[] $all_facets */
+      $all_facets = $this->facetStorage->loadMultiple();
+
+      foreach ($all_facets as $facet) {
+        $machine_name = $facet->id();
+
+        $plugin_derivatives[$machine_name] = [
+          'id' => $base_plugin_id . PluginBase::DERIVATIVE_SEPARATOR . $machine_name,
+          'label' => $this->t('Facet: :facet', [':facet' => $facet->getName()]),
+          'admin_label' => $facet->getName(),
+          'description' => $this->t('Facet'),
+        ] + $base_plugin_definition;
+
+        $sources[] = $this->t('Facet: :facet', [':facet' => $facet->getName()]);
+      }
+
+      $this->derivatives[$base_plugin_id] = $plugin_derivatives;
+    }
+    return $this->derivatives[$base_plugin_id];
+  }
+
+}

src/Plugin/Condition/OtherFacet.php

+<?php
+
+/**
+ * @file
+ * Contains \Drupal\facets\Plugin\Condition\OtherFacet.
+ */
+
+namespace Drupal\facets\Plugin\Condition;
+
+use Drupal\Component\Plugin\PluginBase;
+use Drupal\Core\Block\BlockManager;
+use Drupal\Core\Condition\ConditionPluginBase;
+use Drupal\Core\Entity\EntityStorageInterface;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
+use Drupal\Core\Session\AccountProxyInterface;
+use Drupal\facets\FacetManager\DefaultFacetManager;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Provides an 'other facet' condition.
+ *
+ * This adds a condition plugin to make sure that facets can depend on other
+ * facet's or their values. The facet value is a freeform textfield and works on
+ * both raw and display values of the results.
+ *
+ * @Condition(
+ *   id = "other_facet",
+ *   label = @Translation("Other facet"),
+ * )
+ */
+class OtherFacet extends ConditionPluginBase implements ContainerFactoryPluginInterface {
+
+  /**
+   * The facet entity storage.
+   *
+   * @var \Drupal\Core\Entity\EntityStorageInterface
+   */
+  protected $facetStorage;
+
+  /**
+   * The block plugin manager.
+   *
+   * @var \Drupal\Core\Block\BlockManager
+   */
+  protected $blockManager;
+
+  /**
+   * The user that's currently logged in.
+   *
+   * @var \Drupal\Core\Session\AccountProxyInterface
+   */
+  protected $currentUser;
+
+  /**
+   * The facet manager service.
+   *
+   * @var \Drupal\facets\FacetManager\DefaultFacetManager
+   */
+  protected $facetManager;
+
+  /**
+   * Creates a new instance of the condition.
+   *
+   * @param \Drupal\Core\Entity\EntityStorageInterface $entity_storage
+   *   The entity storage.
+   * @param \Drupal\Core\Block\BlockManager $block_manager
+   *   The block plugin manager.
+   * @param \Drupal\Core\Session\AccountProxyInterface $current_user
+   *   The currently logged in user.
+   * @param \Drupal\facets\FacetManager\DefaultFacetManager $facet_manager
+   *   The default facet manager class.
+   * @param array $configuration
+   *   The plugin configuration, i.e. an array with configuration values keyed
+   *   by configuration option name. The special key 'context' may be used to
+   *   initialize the defined contexts by setting it to an array of context
+   *   values keyed by context names.
+   * @param string $plugin_id
+   *   The plugin_id for the plugin instance.
+   * @param mixed $plugin_definition
+   *   The plugin implementation definition.
+   */
+  public function __construct(EntityStorageInterface $entity_storage, BlockManager $block_manager, AccountProxyInterface $current_user, DefaultFacetManager $facet_manager, array $configuration, $plugin_id, $plugin_definition) {
+    parent::__construct($configuration, $plugin_id, $plugin_definition);
+    $this->facetStorage = $entity_storage;
+    $this->blockManager = $block_manager;
+    $this->currentUser = $current_user;
+    $this->facetManager = $facet_manager;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
+    return new static(
+      $container->get('entity_type.manager')->getStorage('facets_facet'),
+      $container->get('plugin.manager.block'),
+      $container->get('current_user'),
+      $container->get('facets.manager'),
+      $configuration,
+      $plugin_id,
+      $plugin_definition
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
+    $options = [];
+
+    // Loop over all defined blocks and filter them by provider, this builds an
+    // array of blocks that are provided by the facets module.
+    foreach ($this->blockManager->getDefinitions() as $definition) {
+      if ($definition['provider'] == 'facets') {
+        $options[$definition['id']] = $definition['label'];
+      }
+    }
+
+    $form['facets'] = [
+      '#title' => $this->t('Other facet blocks'),
+      '#type' => 'radios',
+      '#options' => $options,
+      '#default_value' => $this->configuration['facets'],
+    ];
+    $form['facet_value'] = [
+      '#title' => $this->t('Facet value'),
+      '#description' => $this->t('Only applies when a facet is already selected.'),
+      '#type' => 'textfield',
+      '#default_value' => $this->configuration['facet_value'],
+    ];
+
+    return parent::buildConfigurationForm($form, $form_state);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {
+    $this->configuration['facets'] = $form_state->getValue('facets');
+    $this->configuration['facet_value'] = $form_state->getValue('facet_value');
+    parent::submitConfigurationForm($form, $form_state);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function summary() {
+    return $this->t(
+      'The facet is @facet also rendered on the same page.',
+      ['@facet' => $this->configuration['facets']]
+    );
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function evaluate() {
+    $allowed_facet_value = $this->configuration['facet_value'];
+    $allowed_facets = $this->configuration['facets'];
+
+    // Return as early as possible when there are no settings for allowed
+    // facets.
+    if (empty($allowed_facets)) {
+      return TRUE;
+    }
+
+    /** @var \Drupal\facets\Plugin\Block\FacetBlock $block_plugin */
+    $block_plugin = $this->blockManager->createInstance($allowed_facets);
+
+    // Allowed facet value is not set, so we only have to check if the block is
+    // shown here by running the access method on the block plugin with the
+    // currently logged in user.
+    if (empty($allowed_facet_value)) {
+      return $block_plugin->access($this->currentUser);
+    }
+
+    // The block plugin id is saved in the schema: BasePluginID:FacetID. This
+    // means we can explode the ID on ':' and the facet id is in the last part
+    // of that result.
+    $block_plugin_id  = $block_plugin->getPluginId();
+    $facet_id = explode(PluginBase::DERIVATIVE_SEPARATOR, $block_plugin_id)[1];
+
+    /** @var \Drupal\facets\FacetInterface $facet */
+    $facet = $this->facetStorage->load($facet_id);
+    $this->facetManager->setFacetSourceId($facet->getFacetSourceId());
+
+    $facet = $this->facetManager->returnProcessedFacet($facet_id);
+
+    foreach ($facet->getResults() as $result) {
+      $is_value = $result->getRawValue() == $allowed_facet_value || $result->getDisplayValue() == $allowed_facet_value;
+      if ($is_value && $result->isActive()) {
+        return TRUE;
+      }
+    }
+
+    return FALSE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function defaultConfiguration() {
+    $config = ['facets' => FALSE, 'facet_value' => FALSE];
+    return $config + parent::defaultConfiguration();
+  }
+
+}

src/Plugin/facets/facet_source/SearchApiBaseFacetSource.php

@@ -10,7 +10,6 @@ use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\StringTranslation\StringTranslationTrait;
 use Drupal\facets\Exception\InvalidQueryTypeException;
 use Drupal\facets\FacetInterface;
-use Drupal\facets\FacetSource\FacetSourcePluginInterface;
 use Drupal\search_api\Backend\BackendInterface;
 use Drupal\facets\FacetSource\FacetSourcePluginBase;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -65,7 +64,7 @@ abstract class SearchApiBaseFacetSource extends FacetSourcePluginBase {
   /**
    * {@inheritdoc}
    */
-  public function buildConfigurationForm(array $form, FormStateInterface $form_state, FacetInterface $facet, FacetSourcePluginInterface $facet_source) {
+  public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
 
     $form['field_identifier'] = [
       '#type' => 'select',
@@ -73,7 +72,7 @@ abstract class SearchApiBaseFacetSource extends FacetSourcePluginBase {
       '#title' => $this->t('Facet field'),
       '#description' => $this->t('Choose the indexed field.'),
       '#required' => TRUE,
-      '#default_value' => $facet->getFieldIdentifier(),
+      '#default_value' => $this->facet->getFieldIdentifier(),
     ];
 
     return $form;
@@ -84,7 +83,7 @@ abstract class SearchApiBaseFacetSource extends FacetSourcePluginBase {
    */
   public function getFields() {
     $indexed_fields = [];
-    $fields = $this->index->getFields(TRUE);
+    $fields = $this->index->getFields();
     foreach ($fields as $field) {
       $indexed_fields[$field->getFieldIdentifier()] = $field->getLabel();
     }
@@ -99,16 +98,17 @@ abstract class SearchApiBaseFacetSource extends FacetSourcePluginBase {
     // identifier.
     $field_id = $facet->getFieldIdentifier();
     // Get the Search API Server.
-    $server = $this->index->getServer();
+    $server = $this->index->getServerInstance();
     // Get the Search API Backend.
     $backend = $server->getBackend();
 
-    $fields = $this->index->getFields(TRUE);
+    $fields = $this->index->getFields();
     foreach ($fields as $field) {
       if ($field->getFieldIdentifier() == $field_id) {
         return $this->getQueryTypesForDataType($backend, $field->getType());
       }
     }
+
     throw new InvalidQueryTypeException($this->t("No available query types were found for facet @facet", ['@facet' => $facet->getName()]));
   }
 

src/Plugin/facets/facet_source/SearchApiViewsPage.php

@@ -75,7 +75,7 @@ class SearchApiViewsPage extends SearchApiBaseFacetSource {
   public function getPath() {
     $view = Views::getView($this->pluginDefinition['view_id']);
     $view->setDisplay($this->pluginDefinition['view_display']);
-    return $view->getDisplay()->getOption('path');
+    return $view->getDisplay()->getPath();
   }
 
   /**

src/Plugin/facets/processor/UrlProcessorHandler.php

+<?php
+
+/**
+ * @file
+ * Contains Drupal\facets\Plugin\facets\processor\UrlProcessorHandler.
+ */
+
+namespace Drupal\facets\Plugin\facets\processor;
+
+use Drupal\facets\Exception\InvalidProcessorException;
+use Drupal\facets\FacetInterface;
+use Drupal\facets\Processor\BuildProcessorInterface;
+use Drupal\facets\Processor\PreQueryProcessorInterface;
+use Drupal\facets\Processor\ProcessorPluginBase;
+
+/**
+ * The URL processor handler triggers the actual url processor.
+ *
+ * The URL processor handler allows managing the weight of the actual URL
+ * processor per Facet.  This handler will trigger the actual.
+ *
+ * @FacetsUrlProcessor, which can be configured on the Facet source.
+ *
+ * @FacetsProcessor(
+ *   id = "url_processor_handler",
+ *   label = @Translation("URL handler"),
+ *   description = @Translation("Triggers the URL processor, which is set in the Facet source configuration."),
+ *   stages = {
+ *     "pre_query" = 50,
+ *     "build" = 15,
+ *   },
+ *   locked = true
+ * )
+ */
+class UrlProcessorHandler extends ProcessorPluginBase implements BuildProcessorInterface, PreQueryProcessorInterface {
+
+  /**
+   * The actual url processor used for handing urls.
+   *
+   * @var \Drupal\facets\UrlProcessor\UrlProcessorInterface
+   */
+  protected $processor;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function __construct(array $configuration, $plugin_id, array $plugin_definition) {
+    parent::__construct($configuration, $plugin_id, $plugin_definition);
+
+    if (!isset($configuration['facet']) || !$configuration['facet'] instanceof FacetInterface) {
+      throw new InvalidProcessorException("The UrlProcessorHandler doesn't have the required 'facet' in the configuration array.");
+    }
+
+    /** @var \Drupal\facets\FacetInterface $facet */
+    $facet = $configuration['facet'];
+
+    /** @var \Drupal\facets\FacetSourceInterface $fs */
+    $fs = $facet->getFacetSourceConfig();
+
+    $url_processor_name = $fs->getUrlProcessorName();
+
+    $manager = \Drupal::getContainer()->get('plugin.manager.facets.url_processor');
+    $this->processor = $manager->createInstance($url_processor_name, ['facet' => $facet]);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function build(FacetInterface $facet, array $results) {
+    return $this->processor->buildUrls($facet, $results);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function preQuery(FacetInterface $facet) {
+    $this->processor->setActiveItems($facet);
+  }
+
+}

src/Plugin/facets/query_type/SearchApiString.php

@@ -29,7 +29,7 @@ use Drupal\facets\Result\Result;
 class SearchApiString extends QueryTypePluginBase {
 
   /**
-   * Holds the backend's native query object.
+   * The backend's native query object.
    *
    * @var \Drupal\search_api\Query\QueryInterface
    */
@@ -41,11 +41,33 @@ class SearchApiString extends QueryTypePluginBase {
   public function execute() {
     $query = $this->query;
 
-    // Alter the query here.
-    if (!empty($query)) {
-      $options = &$query->getOptions();
+    $unfiltered_results = [];
 
+    // Only alter the query when there's an actual query object to alter.
+    if (!empty($query)) {
+      $operator = $this->facet->getQueryOperator();
       $field_identifier = $this->facet->getFieldIdentifier();
+      $exclude = $this->facet->getExclude();
+
+      // Copy the query object so we can do an unfiltered query. We need to have
+      // this unfiltered results to make sure that the count of a facet is
+      // correct. The unfiltered results get returned to the facet manager, the
+      // facet manager will save it on facet::unfiltered_results.
+      $unfiltered_query = $query;
+      $unfiltered_options = &$unfiltered_query->getOptions();
+      $unfiltered_options['search_api_facets'][$field_identifier] = array(
+        'field' => $field_identifier,
+        'limit' => 50,
+        'operator' => 'and',
+        'min_count' => 0,
+        'missing' => FALSE,
+      );
+      $unfiltered_results = $unfiltered_query
+        ->execute()
+        ->getExtraData('search_api_facets');
+
+      // Set the options for the actual query.
+      $options = &$query->getOptions();
       $options['search_api_facets'][$field_identifier] = array(
         'field' => $field_identifier,
         'limit' => 50,
@@ -56,25 +78,36 @@ class SearchApiString extends QueryTypePluginBase {
 
       // Add the filter to the query if there are active values.
       $active_items = $this->facet->getActiveItems();
+
       if (count($active_items)) {
+        $filter = $query->createConditionGroup($operator);
         foreach ($active_items as $value) {
-          $filter = $query->createConditionGroup();
-          $filter->addCondition($this->facet->getFieldIdentifier(), $value);
-          $query->addConditionGroup($filter);
+          $filter->addCondition($this->facet->getFieldIdentifier(), $value, $exclude ? '<>' : '=');
         }
+        $query->addConditionGroup($filter);
       }
     }
+
+    return $unfiltered_results;
   }
 
   /**
    * {@inheritdoc}
    */
   public function build() {
+    $query_operator = $this->facet->getQueryOperator();
+
     if (!empty($this->results)) {
       $facet_results = array();
-      foreach ($this->results as $result) {
-        if ($result['count']) {
-          $facet_results[] = new Result(trim($result['filter'], '"'), trim($result['filter'], '"'), $result['count']);
+      foreach ($this->results as $key => $result) {
+        if ($result['count'] || $query_operator == 'OR') {
+          $count = $result['count'];
+          if ($query_operator === 'OR') {
+            $count = $this->facet->getUnfilteredResults()[$this->facet->getFieldIdentifier()][$key]['count'];
+          }
+
+          $result = new Result(trim($result['filter'], '"'), trim($result['filter'], '"'), $count);
+          $facet_results[] = $result;
         }
       }
       $this->facet->setResults($facet_results);

src/Plugin/facets/processor/QueryStringUrlProcessor.php → src/Plugin/facets/url_processor/QueryString.php

@@ -2,31 +2,26 @@
 
 /**
  * @file
- * Contains Drupal\facets\Plugin\facets\url_processor\UrlProcessorQueryString.
+ * Contains Drupal\facets\Plugin\facets\url_processor\QueryString.
  */
 
-namespace Drupal\facets\Plugin\facets\processor;
+namespace Drupal\facets\Plugin\facets\url_processor;
 
 use Drupal\Core\Url;
 use Drupal\facets\FacetInterface;
-use Drupal\facets\Processor\UrlProcessorPluginBase;
+use Drupal\facets\UrlProcessor\UrlProcessorPluginBase;
 use Symfony\Component\HttpFoundation\Request;
 
 /**
- * The basic url processor, uses query strings.
+ * Query string URL processor.
  *
- * @FacetsProcessor(
+ * @FacetsUrlProcessor(
  *   id = "query_string",
- *   label = @Translation("Query string url processor"),
- *   description = @Translation("Most simple url processor which uses the query sting."),
- *   stages = {
- *     "pre_query" = 50,
- *     "build" = 15,
- *   },
- *   locked = true
+ *   label = @Translation("Query string"),
+ *   description = @Translation("Query string is the default Facets URL processor, and uses GET parameters, e.g. ?f[0]=brand:drupal&f[1]=color:blue")
  * )
  */
-class QueryStringUrlProcessor extends UrlProcessorPluginBase {
+class QueryString extends UrlProcessorPluginBase {
 
   /**
    * A string that separates the filters in the query string.
@@ -38,7 +33,7 @@ class QueryStringUrlProcessor extends UrlProcessorPluginBase {
    *
    * @var string
    */
-  protected $url_alias;
+  protected $urlAlias;
 
   /**
    * An array of active filters.
@@ -59,22 +54,21 @@ class QueryStringUrlProcessor extends UrlProcessorPluginBase {
   /**
    * {@inheritdoc}
    */
-  public function build(FacetInterface $facet, array $results) {
-    // Create links for all the values.
-    // First get the current list of get parameters.
-    $get_params = $this->request->query;
-
-    // Set the url alias from the the facet object.
-    $this->url_alias = $facet->getUrlAlias();
-
+  public function buildUrls(FacetInterface $facet, array $results) {
     // No results are found for this facet, so don't try to create urls.
     if (empty($results)) {
       return [];
     }
 
+    // First get the current list of get parameters.
+    $get_params = $this->request->query;
+
+    // Set the url alias from the the facet object.
+    $this->urlAlias = $facet->getUrlAlias();
+
     /** @var \Drupal\facets\Result\ResultInterface $result */
     foreach ($results as &$result) {
-      $filter_string = $this->url_alias . ':' . $result->getRawValue();
+      $filter_string = $this->urlAlias . self::SEPARATOR . $result->getRawValue();
       $result_get_params = clone $get_params;
 
       $filter_params = $result_get_params->get($this->filterKey, [], TRUE);
@@ -108,20 +102,20 @@ class QueryStringUrlProcessor extends UrlProcessorPluginBase {
   /**
    * {@inheritdoc}
    */
-  public function preQuery(FacetInterface $facet) {
+  public function setActiveItems(FacetInterface $facet) {
     // Set the url alias from the the facet object.
-    $this->url_alias = $facet->getUrlAlias();
+    $this->urlAlias = $facet->getUrlAlias();
 
     // Get the filter key of the facet.
-    if (isset($this->activeFilters[$this->url_alias])) {
-      foreach ($this->activeFilters[$this->url_alias] as $value) {
+    if (isset($this->activeFilters[$this->urlAlias])) {
+      foreach ($this->activeFilters[$this->urlAlias] as $value) {
         $facet->setActiveItem(trim($value, '"'));
       }
     }
   }
 
   /**
-   * Initialize the active filters.
+   * Initializes the active filters.
    *
    * Get all the filters that are active. This method only get's all the
    * filters but doesn't assign them to facets. In the processFacet method the

src/Plugin/facets/widget/CheckboxWidget.php

@@ -7,10 +7,13 @@
 
 namespace Drupal\facets\Plugin\facets\widget;
 
+use Drupal\Core\Form\FormInterface;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\StringTranslation\StringTranslationTrait;
+use Drupal\Core\Url;
 use Drupal\facets\FacetInterface;
 use Drupal\facets\Widget\WidgetInterface;
+use Symfony\Component\HttpFoundation\RedirectResponse;
 
 /**
  * The checkbox / radios widget.
@@ -21,18 +24,10 @@ use Drupal\facets\Widget\WidgetInterface;
  *   description = @Translation("A configurable widget that shows a list of checkboxes"),
  * )
  */
-class CheckboxWidget implements WidgetInterface {
+class CheckboxWidget implements WidgetInterface, FormInterface {
 
   use StringTranslationTrait;
 
-  /**
-   * The link generator.
-   *
-   * @var \Drupal\Core\Utility\LinkGeneratorInterface $linkGenerator
-   *   The link generator.
-   */
-  protected $linkGenerator;
-
   /**
    * {@inheritdoc}
    */
@@ -44,33 +39,14 @@ class CheckboxWidget implements WidgetInterface {
    * {@inheritdoc}
    */
   public function build(FacetInterface $facet) {
-    /** @var \Drupal\facets\Result\Result[] $results */
-    $results = $facet->getResults();
-    $items = [];
-
-    $configuration = $facet->get('widget_configs');
-    $show_numbers = (bool) $configuration['show_numbers'];
+    $form_builder = \Drupal::getContainer()->get('form_builder');
 
-    foreach ($results as $result) {
-      if ($result->getCount()) {
-        // Get the link.
-        $text = $result->getDisplayValue();
-        if ($show_numbers) {
-          $text .= ' (' . $result->getCount() . ')';
-        }
-        if ($result->isActive()) {
-          $text = '(-) ' . $text;
-        }
-        $link = $this->linkGenerator()->generate($text, $result->getUrl());
-        $items[] = $link;
-      }
-    }
-    $build = [
-      '#theme' => 'item_list',
-      '#items' => $items,
-    ];
+    // The form builder's getForm method accepts 1 argument in the interface,
+    // the form ID. Extra arguments get passed into the form states addBuildInfo
+    // method. This way we can pass the facet to the ::buildForm method, it uses
+    // FormState::getBuildInfo to get the facet out.
+    $build = $form_builder->getForm(static::class, $facet);
 
-    $build['#prefix'] = $this->t('Checkboxes');
     return $build;
   }
 
@@ -102,16 +78,102 @@ class CheckboxWidget implements WidgetInterface {
   }
 
   /**
-   * Gets the link generator.
-   *
-   * @return \Drupal\Core\Utility\LinkGeneratorInterface
-   *   The link generator.
+   * {@inheritdoc}
    */
-  protected function linkGenerator() {
-    if (!isset($this->linkGenerator)) {
-      $this->linkGenerator = \Drupal::linkGenerator();
+  public function getFormId() {
+    return 'facets_checkbox_widget';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+
+    /** @var \Drupal\facets\FacetInterface $facet */
+    // Get the facet form the build info, see the remark in ::build to know
+    // where this comes from.
+    $build_info = $form_state->getBuildInfo();
+    $facet = $build_info['args'][0];
+
+    /** @var \Drupal\facets\Result\Result[] $results */
+    $results = $facet->getResults();
+
+    $configuration = $facet->getWidgetConfigs();
+    $show_numbers = (bool) (isset($configuration['show_numbers']) ? $configuration['show_numbers'] : FALSE);
+    $form[$facet->getFieldAlias()] = [
+      '#type' => 'checkboxes',
+      '#title' => $facet->getName(),
+    ];
+
+    $options = array();
+    foreach ($results as $result) {
+      $text = $result->getDisplayValue();
+      if ($show_numbers) {
+        $text .= ' (' . $result->getCount() . ')';
+      }
+
+      $options[$result->getRawValue()] = $text;
+
+      if ($result->isActive()) {
+        $form[$facet->getFieldAlias()]['#default_value'][] = $result->getRawValue();
+      }
+    }
+
+    $form[$facet->getFieldAlias()]['#options'] = $options;
+
+    $form[$facet->id() . '_submit'] = [
+      '#type' => 'submit',
+      '#value' => 'submit',
+    ];
+
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validateForm(array &$form, FormStateInterface $form_state) {}
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) {
+    $values = $form_state->getValues();
+
+    /** @var \Drupal\facets\FacetInterface $facet */
+    $build_info = $form_state->getBuildInfo();
+    $facet = $build_info['args'][0];
+
+    $result_link = FALSE;
+    $active_items = [];
+
+    foreach ($values[$facet->getFieldAlias()] as $key => $value) {
+      if ($value !== 0) {
+        $active_items[] = $value;
+      }
     }
-    return $this->linkGenerator;
+
+    foreach ($facet->getResults() as $result) {
+      if (in_array($result->getRawValue(), $active_items)) {
+        $result_link = $result->getUrl();
+      }
+    }
+
+    // We have an active item, so we redirect to the page that has that facet
+    // selected. This should be an absolute link because RedirectResponse is a
+    // symfony class that requires a full URL.
+    if ($result_link instanceof Url) {
+      $result_link->setAbsolute();
+      $form_state->setResponse(new RedirectResponse($result_link->toString()));
+      return;
+    }
+
+    // The form was submitted but nothing was active in the form, we should
+    // still redirect, but the url for the new page can't come from a result.
+    // So we're redirecting to the facet source's page.
+    $link = Url::fromUri($facet->getFacetSource()->getPath());
+    $link->setAbsolute();
+    $form_state->setResponse(new RedirectResponse($link->toString()));
   }
 
 }

src/Plugin/facets/widget/LinksWidget.php

@@ -8,6 +8,7 @@
 namespace Drupal\facets\Plugin\facets\widget;
 
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Link;
 use Drupal\Core\StringTranslation\StringTranslationTrait;
 use Drupal\facets\FacetInterface;
 use Drupal\facets\Widget\WidgetInterface;
@@ -25,14 +26,6 @@ class LinksWidget implements WidgetInterface {
 
   use StringTranslationTrait;
 
-  /**
-   * The link generator.
-   *
-   * @var \Drupal\Core\Utility\LinkGeneratorInterface $linkGenerator
-   *   The link generator.
-   */
-  protected $linkGenerator;
-
   /**
    * {@inheritdoc}
    */
@@ -48,32 +41,36 @@ class LinksWidget implements WidgetInterface {
     $results = $facet->getResults();
     $items = [];
 
-    $configuration = $facet->get('widget_configs');
-    $show_numbers = (bool) $configuration['show_numbers'];
+    $configuration = $facet->getWidgetConfigs();
+    $show_numbers = empty($configuration['show_numbers']) ? FALSE : (bool) $configuration['show_numbers'];
 
     foreach ($results as $result) {
-      if ($result->getCount()) {
-        // Get the link.
-        $text = $result->getDisplayValue();
-        if ($show_numbers) {
-          $text .= ' (' . $result->getCount() . ')';
-        }
-        if ($result->isActive()) {
-          $text = '(-) ' . $text;
-        }
-
-        if (is_null($result->getUrl())) {
-          $items[] = $text;
-        }
-        else {
-          $items[] = $this->linkGenerator()->generate($text, $result->getUrl());
-        }
+      // Get the link.
+      $text = $result->getDisplayValue();
+      if ($show_numbers) {
+        $text .= ' (' . $result->getCount() . ')';
+      }
+      if ($result->isActive()) {
+        $text = '(-) ' . $text;
+      }
+
+      if (is_null($result->getUrl())) {
+        $items[] = $text;
+      }
+      else {
+        $items[] = new Link($text, $result->getUrl());
       }
     }
 
     $build = [
       '#theme' => 'item_list',
       '#items' => $items,
+      '#cache' => [
+        'contexts' => [
+          'url.path',
+          'url.query_args',
+        ],
+      ],
     ];
     return $build;
   }
@@ -107,17 +104,4 @@ class LinksWidget implements WidgetInterface {
     return $query_types['string'];
   }
 
-  /**
-   * Gets the link generator.
-   *
-   * @return \Drupal\Core\Utility\LinkGeneratorInterface
-   *   The link generator.
-   */
-  protected function linkGenerator() {
-    if (!isset($this->linkGenerator)) {
-      $this->linkGenerator = \Drupal::linkGenerator();
-    }
-    return $this->linkGenerator;
-  }
-
 }

src/Processor/BuildProcessorInterface.php

@@ -16,7 +16,7 @@ use Drupal\facets\FacetInterface;
 interface BuildProcessorInterface extends ProcessorInterface {
 
   /**
-   * Processor runs before the renderable array is created.
+   * Runs before the renderable array is created.
    *
    * @param \Drupal\facets\FacetInterface $facet
    *   The facet being changed.

src/Processor/PostQueryProcessorInterface.php

@@ -14,7 +14,7 @@ namespace Drupal\facets\Processor;
 interface PostQueryProcessorInterface extends ProcessorInterface {
 
   /**
-   * Processor runs after the query was executed.
+   * Runs after the query was executed.
    *
    * Uses the query results and can alter those results, for example a
    * ValueCallbackProcessor.

src/Processor/PreQueryProcessorInterface.php

@@ -15,7 +15,7 @@ use Drupal\facets\FacetInterface;
 interface PreQueryProcessorInterface extends ProcessorInterface {
 
   /**
-   * Processor runs before the query is executed.
+   * Runs before the query is executed.
    *
    * Uses the queryType and the facetSource implementation to make sure the
    * alteration to the query was added before the query is executed in the

src/Processor/ProcessorPluginBase.php

@@ -28,8 +28,7 @@ class ProcessorPluginBase extends PluginBase implements ProcessorInterface {
   /**
    * {@inheritdoc}
    */
-  public function validateConfigurationForm(array $form, FormStateInterface $form_state, FacetInterface $facet) {
-  }
+  public function validateConfigurationForm(array $form, FormStateInterface $form_state, FacetInterface $facet) {}
 
   /**
    * {@inheritdoc}

src/Processor/WidgetOrderPluginBase.php

@@ -11,7 +11,7 @@ use Drupal\Core\Form\FormStateInterface;
 use Drupal\facets\FacetInterface;
 
 /**
- * A base class for plugins that implements most of the boilerplate.
+ * A base class for plugins that implements some boilerplate for a widget order.
  */
 abstract class WidgetOrderPluginBase extends ProcessorPluginBase implements WidgetOrderProcessorInterface {
 

src/Processor/WidgetOrderProcessorInterface.php

@@ -13,7 +13,7 @@ namespace Drupal\facets\Processor;
 interface WidgetOrderProcessorInterface extends BuildProcessorInterface {
 
   /**
-   * Order results and return the new order of results.
+   * Orders results and return the new order of results.
    *
    * @param \Drupal\facets\Result\Result[] $results
    *   An array containing results.

src/QueryType/QueryTypeInterface.php

@@ -12,12 +12,15 @@ namespace Drupal\facets\QueryType;
 interface QueryTypeInterface {
 
   /**
-   * Add facet info to the query using the backend native query object.
+   * Adds facet info to the query using the backend native query object.
+   *
+   * @return array
+   *   Returns an array of unfiltered results
    */
   public function execute();
 
   /**
-   * Build the facet information, so it can be rendered.
+   * Builds the facet information, so it can be rendered.
    */
   public function build();
 

src/QueryType/QueryTypePluginBase.php

@@ -28,7 +28,7 @@ abstract class QueryTypePluginBase extends PluginBase implements QueryTypeInterf
   }
 
   /**
-   * Holds the backend native query object.
+   * The backend native query object.
    *
    * @var \Drupal\search_api\Query\Query $query
    */
@@ -42,7 +42,7 @@ abstract class QueryTypePluginBase extends PluginBase implements QueryTypeInterf
   protected $facet;
 
   /**
-   * Holds the results for the facet.
+   * The results for the facet.
    *
    * @var \Drupal\facets\Result\ResultInterface[]
    */

src/Result/Result.php

@@ -45,7 +45,7 @@ class Result implements ResultInterface {
   protected $active = FALSE;
 
   /**
-   * Construct a new instance of the value object.
+   * Constructs a new result value object.
    *
    * @param mixed $raw_value
    *   The raw value.

src/Result/ResultInterface.php

@@ -15,7 +15,7 @@ use Drupal\Core\Url;
 interface ResultInterface {
 
   /**
-   * Get the raw value as present in the index.
+   * Returns the raw value as present in the index.
    *
    * @return string
    *   The raw value of the result.
@@ -23,7 +23,7 @@ interface ResultInterface {
   public function getRawValue();
 
   /**
-   * Get the display value as present in the index.
+   * Returns the display value as present in the index.
    *
    * @return string
    *   The formatted value of the result.
@@ -31,7 +31,7 @@ interface ResultInterface {
   public function getDisplayValue();
 
   /**
-   * Get the count for the result.
+   * Returns the count for the result.
    *
    * @return mixed
    *   The amount of items for the result.
@@ -39,7 +39,7 @@ interface ResultInterface {
   public function getCount();
 
   /**
-   * Get the url.
+   * Returns the url.
    *
    * @return \Drupal\Core\Url
    *   The url of the search page with the facet url appended.
@@ -47,7 +47,7 @@ interface ResultInterface {
   public function getUrl();
 
   /**
-   * Set the url.
+   * Sets the url.
    *
    * @param \Drupal\Core\Url $url
    *   The url of the search page with the facet url appended.
@@ -55,7 +55,7 @@ interface ResultInterface {
   public function setUrl(Url $url);
 
   /**
-   * Indicate that the value is active (selected).
+   * Indicates that the value is active (selected).
    *
    * @param bool $active
    *   A boolean indicating the active state.
@@ -71,7 +71,7 @@ interface ResultInterface {
   public function isActive();
 
   /**
-   * Override the display value of a result.
+   * Overrides the display value of a result.
    *
    * @param string $display_value
    *   Override display value.

src/Tests/ExampleContentTrait.php

@@ -8,7 +8,6 @@
 namespace Drupal\facets\Tests;
 
 use Drupal\search_api\Entity\Index;
-use Drupal\search_api\Utility;
 
 /**
  * Contains helpers to create data that can be used by tests.
@@ -36,44 +35,45 @@ trait ExampleContentTrait {
   protected function insertExampleContent() {
     $count = \Drupal::entityQuery('entity_test')->count()->execute();
 
-    $entity_test_storage = \Drupal::entityManager()->getStorage('entity_test');
+    $entity_test_storage = \Drupal::entityTypeManager()
+      ->getStorage('entity_test');
     $this->entities[1] = $entity_test_storage->create(array(
-        'name' => 'foo bar baz',
-        'body' => 'test test',
-        'type' => 'item',
-        'keywords' => array('orange'),
-        'category' => 'item_category'
-      ));
+      'name' => 'foo bar baz',
+      'body' => 'test test',
+      'type' => 'item',
+      'keywords' => array('orange'),
+      'category' => 'item_category',
+    ));
     $this->entities[1]->save();
     $this->entities[2] = $entity_test_storage->create(array(
-        'name' => 'foo test',
-        'body' => 'bar test',
-        'type' => 'item',
-        'keywords' => array('orange', 'apple', 'grape'),
-        'category' => 'item_category'
-      ));
+      'name' => 'foo test',
+      'body' => 'bar test',
+      'type' => 'item',
+      'keywords' => array('orange', 'apple', 'grape'),
+      'category' => 'item_category',
+    ));
     $this->entities[2]->save();
     $this->entities[3] = $entity_test_storage->create(array(
-        'name' => 'bar',
-        'body' => 'test foobar',
-        'type' => 'item',
-      ));
+      'name' => 'bar',
+      'body' => 'test foobar',
+      'type' => 'item',
+    ));
     $this->entities[3]->save();
     $this->entities[4] = $entity_test_storage->create(array(
-        'name' => 'foo baz',
-        'body' => 'test test test',
-        'type' => 'article',
-        'keywords' => array('apple', 'strawberry', 'grape'),
-        'category' => 'article_category'
-      ));
+      'name' => 'foo baz',
+      'body' => 'test test test',
+      'type' => 'article',
+      'keywords' => array('apple', 'strawberry', 'grape'),
+      'category' => 'article_category',
+    ));
     $this->entities[4]->save();
     $this->entities[5] = $entity_test_storage->create(array(
-        'name' => 'bar baz',
-        'body' => 'foo',
-        'type' => 'article',
-        'keywords' => array('orange', 'strawberry', 'grape', 'banana'),
-        'category' => 'article_category'
-      ));
+      'name' => 'bar baz',
+      'body' => 'foo',
+      'type' => 'article',
+      'keywords' => array('orange', 'strawberry', 'grape', 'banana'),
+      'category' => 'article_category',
+    ));
     $this->entities[5]->save();
     $count = \Drupal::entityQuery('entity_test')->count()->execute() - $count;
     $this->assertEqual($count, 5, "$count items inserted.");
@@ -89,37 +89,9 @@ trait ExampleContentTrait {
    *   The number of successfully indexed items.
    */
   protected function indexItems($index_id) {
+    /** @var \Drupal\search_api\IndexInterface $index */
     $index = Index::load($index_id);
     return $index->indexItems();
   }
 
-  /**
-   * Returns the internal field ID for the given entity field name.
-   *
-   * @param string $field_name
-   *   The field name.
-   *
-   * @return string
-   *   The internal field ID.
-   */
-  protected function getFieldId($field_name) {
-    return Utility::createCombinedId('entity:entity_test', $field_name);
-  }
-
-  /**
-   * Returns the item IDs for the given entity IDs.
-   *
-   * @param array $entity_ids
-   *   An array of entity IDs.
-   *
-   * @return string[]
-   *   An array of item IDs.
-   */
-  protected function getItemIds(array $entity_ids) {
-    $translate_ids = function ($entity_id) {
-      return Utility::createCombinedId('entity:entity_test', $entity_id . ':en');
-    };
-    return array_map($translate_ids, $entity_ids);
-  }
-
 }