✨ Introduce controllerutil.Object interface

[ruromero]

Signed-off-by: ruromero rromerom@redhat.com

Introduce an interface that combines metav1.Object and runtime.Object as discussed in #594

The main purpose of this interface is to reduce type conversions between the two and provide generic method signatures that can show potential errors at compile time and help developers to write simpler code.

This can make reconsider many places in this library and dependent ones its usage each time a cast is done, usually like the following:

//metav1.Object -> runtime.Object
ro, ok := owner.(runtime.Object)

//runtime.Object -> metav1.Object
o, err := meta.Accessor(obj)

An example where this interface can be used is https://github.com/kubernetes-sigs/controller-runtime/blob/master/pkg/controller/controllerutil/controllerutil.go#L95

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[ruromero]

Added CLA

[joelanford]

As @Adirio mentioned here, it might be useful to figure out where we're currently making type assertions in one direction or the other and decide whether we want to update those function signatures as well.

Not sure if that's a blocker for introducing the type though.

Lastly, I know I mentioned in an SDK issue that we should discuss adding this union type to controller-runtime, but now that I'm looking closer and see that metav1.Object and runtime.Object are both provided by k8s.io/apimachinery I wonder if we should pursue adding this there?

[joelanford]

Given that this is a union of two *.Object types would it be more intuitive for this to also include Object in the name?

Also, I wonder if the client package is the most appropriate place for this type. Nothing is really jumping out to me as an alternate though. Perhaps pkg/controller/controllerutil? 🤷‍♂️

[ruromero]

Renamed and moved

[DirectXMan12]

decide whether we want to update those function signatures as well.

Yeah, I think we want to do that. I think there's actually situations where some of those aren't a breaking change (I seem to recall adding additional interfaces to a compound interface casts transparently or something, but I'd have to double check).

[vincepri]

Given that this lives under controllerutil, could we just call it Object instead of KubernetesObject ?

[vincepri]

/ok-to-test

[ruromero]

renamed @vincepri

[vincepri]

/lgtm
/assign @DirectXMan12

[vincepri]

/retitle ✨ Introduce controllerutil.Object interface

[vincepri]

/approve

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[APPROVALNOTIFIER] This PR is APPROVED

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

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[vincepri]

Should we backport this? I'd be useful for other projects as well

[luxas]

Thanks for this change 💯!
I'd love to have this under core k8s.io/apimachinery.
Would someone be up for "backporting" this to there?

[vincepri]

@luxas Happy to help, although need some pointers to where we should place this interface :)

[luxas]

Without knowing exactly, maybe https://pkg.go.dev/k8s.io/apimachinery@v0.18.5/pkg/api/meta?tab=doc would be a good place?