Allow page view derived Advanced Search blocks on any page (#843)

* Allow page view derived Advanced Search blocks on any page

Allows the Advanced Search block to be used on pages
where its corresponding view is not present. Now it
will redirect to the route associated with the view
it was generated from.

This is not valid for Advanced Search blocks that
are derived from non-page based views, as there is
no known location in which to redirect the query.

* Fix for undefined index warning.

* Documented Exposed form style settings requirement for Advanced Search.

src/Form/AdvancedSearchForm.php

@@ -5,10 +5,15 @@ namespace Drupal\islandora_advanced_search\Form;
 use Drupal\Component\Utility\Html;
 use Drupal\Core\Form\FormBase;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Routing\RouteMatchInterface;
 use Drupal\Core\StringTranslation\TranslatableMarkup;
 use Drupal\islandora_advanced_search\AdvancedSearchQuery;
 use Drupal\islandora_advanced_search\AdvancedSearchQueryTerm;
 use Drupal\islandora_advanced_search\GetConfigTrait;
+use Drupal\views\DisplayPluginCollection;
+use Drupal\views\Entity\View;
+use Drupal\views\Plugin\views\display\PathPluginBase;
+use Drupal\views\Views;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\HttpFoundation\Request;
 
@@ -46,11 +51,19 @@ class AdvancedSearchForm extends FormBase {
    */
   protected $request;
 
+  /**
+   * The current route match.
+   *
+   * @var \Drupal\Core\Routing\RouteMatchInterface
+   */
+  protected $currentRouteMatch;
+
   /**
    * Class constructor.
    */
-  public function __construct(Request $request) {
+  public function __construct(Request $request, RouteMatchInterface $current_route_match) {
     $this->request = $request;
+    $this->currentRouteMatch = $current_route_match;
   }
 
   /**
@@ -58,7 +71,8 @@ class AdvancedSearchForm extends FormBase {
    */
   public static function create(ContainerInterface $container) {
     return new static(
-      $container->get('request_stack')->getMasterRequest()
+      $container->get('request_stack')->getMasterRequest(),
+      $container->get('current_route_match')
     );
   }
 
@@ -186,13 +200,39 @@ class AdvancedSearchForm extends FormBase {
     return [$recursive, $term_values];
   }
 
+  /**
+   * Gets the route name for the view display used to derive this forms block.
+   *
+   * @return string|null
+   *   The route name for the view display that was used to create this
+   *   forms block.
+   */
+  protected function getRouteName(FormStateInterface $form_state) {
+    $view = $form_state->get('view');
+    $display = $form_state->get('display');
+    $display_handlers = new DisplayPluginCollection($view->getExecutable(), Views::pluginManager('display'));
+    $display_handler = $display_handlers->get($display['id']);
+    if ($display_handler instanceof PathPluginBase) {
+      return $display_handler->getRouteName();
+    }
+    return NULL;
+  }
+
   /**
    * {@inheritdoc}
    */
-  public function buildForm(array $form, FormStateInterface $form_state, array $fields = [], string $context_filter = NULL) {
+  public function buildForm(array $form, FormStateInterface $form_state, View $view = NULL, array $display = [], array $fields = [], string $context_filter = NULL) {
+    // Keep reference to view and display as the submit handler may use them
+    // to redirect the user to the search page.
+    $form_state->set('view', $view);
+    $form_state->set('display', $display);
+    $route_name = $this->getRouteName($form_state);
+    $requires_redirect = $route_name ? $this->currentRouteMatch->getRouteName() !== $route_name : FALSE;
+
     $form['#attached']['library'][] = 'islandora_advanced_search/advanced.search.form';
     $form['#attached']['drupalSettings']['islandora_advanced_search_form'] = [
       'id' => Html::getId($this->getFormId()),
+      'redirect' => $requires_redirect,
       'query_parameter' => AdvancedSearchQuery::getQueryParameter(),
       'recurse_parameter' => AdvancedSearchQuery::getRecurseParameter(),
       'mapping' => [
@@ -352,9 +392,10 @@ class AdvancedSearchForm extends FormBase {
       $terms[] = AdvancedSearchQueryTerm::fromUserInput($term);
     }
     $terms = array_filter($terms);
-    $recurse = filter_var($values['recursive'], FILTER_VALIDATE_BOOLEAN);
+    $recurse = filter_var(isset($values['recursive']) ? $values['recursive'] : FALSE, FILTER_VALIDATE_BOOLEAN);
+    $route = $this->getRouteName($form_state);
     $advanced_search_query = new AdvancedSearchQuery();
-    return $advanced_search_query->toUrl($this->request, $terms, $recurse);
+    return $advanced_search_query->toUrl($this->request, $terms, $recurse, $route);
   }
 
   /**