Provide a Views argument handler for filtering assets by group.

modules/asset/group/farm_group.module

@@ -41,6 +41,9 @@ function farm_group_views_data_alter(array &$data) {
       'id' => 'asset_group',
       'field_name' => 'group',
     ],
+    'argument' => [
+      'id' => 'asset_group',
+    ],
   ];
 }
 

modules/asset/group/src/Plugin/views/argument/AssetGroup.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace Drupal\farm_group\Plugin\views\argument;
+
+use Drupal\views\Plugin\views\argument\ArgumentPluginBase;
+
+/**
+ * An argument for filtering assets by their current group.
+ *
+ * @ingroup views_argument_handlers
+ *
+ * @ViewsArgument("asset_group")
+ */
+class AssetGroup extends ArgumentPluginBase {
+
+  /**
+   * {@inheritdoc}
+   *
+   * @see \Drupal\farm_location\Plugin\views\argument\AssetLocation
+   */
+  public function query($group_by = FALSE) {
+
+    // First query for a list of asset IDs in the group, then use this list to
+    // filter the current View.
+    // We do this in two separate queries for a few reasons:
+    // 1. The Drupal and Views query APIs do not support the kind of compound
+    // JOIN that we use in the group.membership service's getMembers().
+    // 2. We need to allow other modules to override the group.membership
+    // service to provide their own location logic. They shouldn't have to
+    // override this Views argument handler as well.
+    // 3. It keeps this Views argument handler's query modifications very
+    // simple. It only needs the condition: "WHERE asset.id IN (:asset_ids)".
+    // See https://www.drupal.org/project/farm/issues/3217184 for more info.
+    $group = \Drupal::entityTypeManager()->getStorage('asset')->load($this->argument);
+    $assets = \Drupal::service('group.membership')->getGroupMembers($group);
+    $asset_ids = [];
+    foreach ($assets as $asset) {
+      $asset_ids[] = $asset->id();
+    }
+
+    // Filter to only include assets with those IDs.
+    $this->ensureMyTable();
+    $this->query->addWhere(0, "$this->tableAlias.id", $asset_ids, 'IN');
+  }
+
+}