Circular reference detected for service "hook_event_dispatcher.module_handler"

I also have the issue at the moment, but only when enabling SDC, otherwise it was working well.

I'm going to test more.

I think it's attached to this issue: https://www.drupal.org/project/tracer/issues/3387444 🐛 Typed property Drupal\tracer\EventDispatcher\TraceableEventDispatcher::$tracer must not be accessed before initialization Fixed
After installing the update for Tracer(1.0.1), the issue got sorted.

I think it's attached to this issue: https://www.drupal.org/project/tracer/issues/3387444 🐛 Typed property Drupal\tracer\EventDispatcher\TraceableEventDispatcher::$tracer must not be accessed before initialization Fixed
After installing the update for Tracer(1.0.1), the issue got sorted.

The Tracer update didn't sort the issue out after all.
Hotfix patch is provided.

This also only occurred for me once I installed webprofiler. hook_event_dispatcher was working fine before then. Given that this is the case for others as well maybe this issue should be closed in favour of the related one in tracer?

Automatically closed - issue fixed for 2 weeks with no activity.

This problem has resurfaced for us:

hook_event_dispatcher: 4.2.0
tracer: 1.0.4
drupal core: 10.4.5
We are running lando with a pantheon recipe (if that matters).

When hook_event_dispatcher and tracer are enabled, and one runs drush updb, the following error results:

Circular reference detected for service "hook_event_dispatcher.module_handler", path: "hook_event_dispatcher.module_handler -> hook_event_dispatcher.manager -> hook_event_dispatcher.module_handler".

Some guesses as to why this is:

This error occurs during updb, because it has a special bootstrap mode that ensures all modules are loaded and update hooks are discovered in a single run, so it is instantiating the whole thing at once, and bringing the circular reference to light. Whereas in a normal page request, some services are only loaded on demand.

Tracer’s services include:

plugin.manager.tracer:
class: Drupal\tracer\TracerPluginManager
parent: default_plugin_manager

TracerPluginManager extends Drupal’s DefaultPluginManager. That core base class automatically loads the module_handler. If you then have a circular dependency from module_handler → hook_event_dispatcher.manager → module_handler, enabling Tracer is the catalyst that triggers it during drush updb. \Drupal\tracer\TracerPluginManager extends DefaultPluginManager and calls parent::__construct. This parent class requires module_handler.

I will add an issue for tracer and cross-reference this, since I don't have enough understanding to know where the fix would reside, if a fix is possible.

Curious to see if this is reproducible by others.