Entity references can result in multiple builds

Attaching a patch of the proposed solution

The last submitted patch, 2: 3345885-2.patch, failed testing. View results →
- codesniffer_fixes.patch Interdiff of automated coding standards fixes only.

Fixing test failures

Modifies the patch to use KernelEvents::TERMINATE event so that the builds are triggered when using $entity->save();.

Seems like a good idea, but we'll probably need to manually check the state in tests and trigger.

There's also \Drupal\Core\DestructableInterface in core which can be used instead of the terminate event

+++ b/src/EventSubscriber/BuildHooksResponseSubscriber.php
@@ -0,0 +1,52 @@
+      $this->trigger->deployFrontendEntityUpdateEnvironments();

this should delete the state flag too right? otherwise it just keeps triggering?

Using the needs_destruction tag is a good idea but I think that (and now that i'm thinking about it - the terminate event) occur too late in the lifecycle to invalidate the cache tag and write a message using the messenger service.

The deployFrontendEntityUpdateEnvironments will delete the state flag which should prevent multiple runs.

I've attached a revised patch

Looks like there's some failing tests here