✨ Add reconcile.ObjectReconciler

[JamesOwenHall]

Part of #2582.
Fixes #2221.

This PR adds a new reconcile.ObjectReconciler interface to eliminate the following common boilerplate.

func (r *MyReconciler) Reconcile(ctx context.Context, req reconcile.Request) (reconcile.Result, error) {
	example := &examplev1.Example{}
	if err := r.Get(ctx, req.NamespacedName, example); err != nil {
		return ctrl.Result{}, client.IgnoreNotFound(err)
	}

	// Do business logic…
}

ObjectReconciler leverages generics to write reconcilers in terms of deserialized instances of client.Object. It does not replace the existing reconcile.Reconciler interface.

Developers can create a controller with an ObjectReconciler by calling the AsReconciler function.

builder.ControllerManagedBy(manager).
	For(&corev1.ConfigMap{}).
	Complete(reconcile.AsReconciler(client, &MyObjectReconciler{}))

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: JamesOwenHall / name: James Hall (d1cec9c, f78e663, 38c8884)

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[JamesOwenHall]

In #2582 (comment), @alvaroaleman proposed adding a new method to builder.Builder so that an adapter function like AsReconciler here wouldn't be necessary. However, Go does not allow a method to add new type parameters, only a method receiver can define type parameters. Therefore, I believe that adding a Builder.CompleteObjectReconciler method would only be possible if Builder defined a type parameter, i.e. Builder[T client.Object]. I don't think this type parameter makes much sense for instances of reconcile.Reconciler so I opted to use an adapter function instead.

[alvaroaleman]

I actually realized the same thing later on while being on a walk, so agree 👍

[alvaroaleman]

/ok-to-test

[troy0820]

I'm not sure what else this needs but after reviewing it, it looks good to me.

/lgtm

[alvaroaleman]

So @vincepri @sbueringer and myself had a bit of discussion around this and weren't really sure if this is what we want. Given that this is a rather trivial change that can easily be managed downstream, we'd like to defer merging this for now.

We can probably use one of the issues to discuss this and see if we can up with something everyone is comfortable with.

[alvaroaleman]

/hold

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: JamesOwenHall, vincepri

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• OWNERS [vincepri]

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[alvaroaleman]

/hold cancel
nvm, looks like ppl are actually fine with it. Thanks for your work :)