Add a simple access handler for plan_record entities that checks plan entity access.

modules/core/plan/src/Access/PlanRecordAccess.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace Drupal\plan\Access;
+
+use Drupal\Core\Access\AccessResult;
+use Drupal\Core\Entity\EntityAccessControlHandler;
+use Drupal\Core\Entity\EntityInterface;
+use Drupal\Core\Session\AccountInterface;
+
+/**
+ * Defines plan_record access logic.
+ */
+class PlanRecordAccess extends EntityAccessControlHandler {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function checkAccess(EntityInterface $entity, $operation, AccountInterface $account) {
+
+    // If a plan is referenced, access is based on access to the plan.
+    /** @var \Drupal\plan\Entity\PlanInterface[] $plans */
+    $plans = $entity->get('plan')->referencedEntities();
+    if (!empty($plans[0])) {
+      return AccessResult::allowedIf($plans[0]->access($operation, $account));
+    }
+
+    // Otherwise, delegate to the parent method.
+    return parent::checkAccess($entity, $operation, $account);
+  }
+
+}

modules/core/plan/src/Entity/PlanRecord.php

@@ -23,6 +23,9 @@ use Drupal\Core\Field\BaseFieldDefinition;
  *     singular = "@count plan record relationship",
  *     plural = "@count plan record relationships",
  *   ),
+ *   handlers = {
+ *     "access" = "Drupal\plan\Access\PlanRecordAccess",
+ *   },
  *   base_table = "plan_record",
  *   data_table = "plan_record_data",
  *   entity_keys = {