Accept empty group name and domain

[Adirio]

The "core" builtin api group contains Resources such as Pod or Namespace (full list).

This group's uses both an empty group and an empty domain.

Currently, while one of domain or group ar allowed to be empty, both are not allowed to be empty.

/kind bug

[camilamacedo86]

In my POV the error/bug is NOT regarding not allow be both empty, but its logic. And might I would consider it an RFE to support core types. See:

By running kubebuilder create api --group core --version v1 --kind Pod --resource=false --controller=true;

$ kubebuilder create api --group core --version v1 --kind Pod --force
Create Resource [y/n]
n
Create Controller [y/n]
y
Writing scaffold for you to edit...
controllers/pod_controller.go
Running make:
$ make generate
go: creating new go.mod: module tmp
Downloading sigs.k8s.io/controller-tools/cmd/[email protected]
go: found sigs.k8s.io/controller-tools/cmd/controller-gen in sigs.k8s.io/controller-tools v0.4.1
/Users/camilamacedo/go/src/example/bin/controller-gen object:headerFile="hack/boilerplate.go.txt" paths="./..."

I'd expected that the controller was created using/importing the Pod core type and that the PROJECT file would store an empty string for the domain. However, if I asked to generate the resource in the project then, it would no longer be related to the core type besides the name and the resource.domain should equal the project domain.

So, the above scenario results now in:

 $ cat PROJECT 
domain: my.domain
layout: go.kubebuilder.io/v3
projectName: example
repo: example
version: "3"

When should be

domain: my.domain
layout: go.kubebuilder.io/v3
projectName: example
repo: example
resources:
- controller: true
  group: core
  kind: Pod
  path: k8s.io/core/apps/v1
  version: v1
version: "3"

Also, its controller is missing the import for the core api.

Is it make sense?

[Adirio]

I don't consider this a bug (probably i used the bug template)
/remove-kind bug
/kind feature

There is definetely a need to fully support core types, but this is not talking about that. This is a pre-requisite for that.
One of the many core groups is the so called "core" api group. The problem is that this group has an empty Group and Domain, both, and currently the Resource validation only allows one of them to be empty not both. It's not as simple as removing that check because there are some places in the scaffolded files, like the import alias or fully qualified group name where it expects at least one to be non-empty and would result in errors at scaffolding.

[camilamacedo86]

As we spoke in the kb meeting, we agreed in close this one but we will raise a new one just to discuss and see how we can address the problem "how to support external types".

[camilamacedo86]

c/c @estroz

[estroz]

See #1999