Only show "Members" tab on group assets.

modules/asset/group/farm_group.services.yml

@@ -3,3 +3,12 @@ services:
     class: Drupal\farm_group\GroupMembership
     arguments:
       [ '@farm.log_query', '@entity_type.manager', '@datetime.time', '@database' ]
+  farm_group.route_subscriber:
+    class: Drupal\farm_group\Routing\RouteSubscriber
+    tags:
+      - { name: event_subscriber }
+  farm_group.group_members_access:
+    class: Drupal\farm_group\Access\FarmGroupMembersViewsAccessCheck
+    arguments: [ '@entity_type.manager' ]
+    tags:
+      - { name: access_check, applies_to: _group_members_access }

modules/asset/group/src/Access/FarmGroupMembersViewsAccessCheck.php

@@ -0,0 +1,56 @@
+<?php
+
+namespace Drupal\farm_group\Access;
+
+use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\Core\Routing\Access\AccessInterface;
+use Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\Core\Access\AccessResult;
+
+/**
+ * Checks access for displaying Views of group members.
+ */
+class FarmGroupMembersViewsAccessCheck implements AccessInterface {
+
+  /**
+   * The asset storage.
+   *
+   * @var \Drupal\Core\Entity\EntityStorageInterface
+   */
+  protected $assetStorage;
+
+  /**
+   * FarmGroupMembersViewsAccessCheck constructor.
+   *
+   * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
+   *   The entity type manager service.
+   */
+  public function __construct(EntityTypeManagerInterface $entity_type_manager) {
+    $this->assetStorage = $entity_type_manager->getStorage('asset');
+  }
+
+  /**
+   * A custom access check.
+   *
+   * @param \Drupal\Core\Routing\RouteMatchInterface $route_match
+   *   The route match.
+   */
+  public function access(RouteMatchInterface $route_match) {
+
+    // If there is no "asset" parameter, bail.
+    $asset_id = $route_match->getParameter('asset');
+    if (empty($asset_id)) {
+      return AccessResult::allowed();
+    }
+
+    // Allow access if the asset is a group.
+    /** @var \Drupal\asset\Entity\AssetInterface $asset */
+    $asset = $this->assetStorage->load($asset_id);
+    $access = AccessResult::allowedIf($asset->bundle() == 'group');
+
+    // Invalidate the access result when assets are changed.
+    $access->addCacheTags(["asset_list"]);
+    return $access;
+  }
+
+}

modules/asset/group/src/Routing/RouteSubscriber.php

@@ -0,0 +1,27 @@
+<?php
+
+namespace Drupal\farm_group\Routing;
+
+use Drupal\Core\Routing\RouteSubscriberBase;
+use Symfony\Component\Routing\RouteCollection;
+
+/**
+ * Alter routes for the farm_group module.
+ *
+ * @ingroup farm
+ */
+class RouteSubscriber extends RouteSubscriberBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function alterRoutes(RouteCollection $collection) {
+
+    // Add our _group_members_access requirement to
+    // view.farm_group_members.page.
+    if ($route = $collection->get('view.farm_group_members.page')) {
+      $route->setRequirement('_group_members_access', 'Drupal\farm_group\Access\FarmGroupMembersViewsAccessCheck::access');
+    }
+  }
+
+}