Add the action instance to the request environment

[tombruijn]

I created a new topic on the Hanami Discourse about improving the AppSignal APM instrumentation.

To group requests, we would like to know what action it took place in. This information is currently not available in the request environment.

For us, the easiest would be to access the action instance. That gives us the class information and a way to access the params_class to fetch all the parameters of the request: query params and the body payload.

This change adds the action instance on a new request environment key hanami.action_instance.

I had to update one test to not fail on the action instance being returned, which is not important for that spec I think.

Closes #445

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Let me know what you think!

[timriley]

Hi @tombruijn!! Thanks for your patience with this one.

The Hanami 2.2 release is happening in a couple of days, and I've found myself with enough time to look at getting this PR in.

I'd done some changes to the params handling and tests in this repo, so I've rebased over the main branch and force pushed to this PR's branch, I hope you don't mind.

I've also made one other change (this commit): I delayed setting env[ACTION_INSTANCE] until the end of Hanami::Action#call. This way when users are doing simplistic unit tests of actions and passing params as a plain hash (an affordance we allow to simplify testing), they won't have to worry about a confusing "hanami.action_instance" key being a part of their params every time.

I've looked at the way you inspect the env for Rails' "action_controller.instance", and it seems like this is done after the controller/Rack app has been called, so it would seem to be that in our case you wouldn't be sensitive to when we set the env["hanami.action_instance"], so long as it's there by the time the action call is completed. Is that right?

I'm sorry for the short notice, but if you can confirm this in the next day or two, I'll be able to include this in the Hanami 2.2 release, which would be wonderful 😄

Thanks!

[timriley]

You know what? I might just go ahead and merge this. I suspect it'll still do the trick, and if we need to adjust it, that's easy to do in a patch release :)

[tombruijn]

I've looked at the way you inspect the env for Rails' "action_controller.instance", and it seems like this is done after the controller/Rack app has been called, so it would seem to be that in our case you wouldn't be sensitive to when we set the env["hanami.action_instance"], so long as it's there by the time the action call is completed. Is that right?

Hi @timriley! That seems good 👍 Most of our instrumentations set things like the action name after the request is done already. We've found a lot of libraries don't know things like the action name, parsed params, route name, etc. beforehand, so our gem can handle this order of data being available.

Thanks for updating it and merging it! We'll update our Ruby gem to take advantage of it so we have to do no/less monkeypatching for Hanami 😁