Empty "Items" object for array in generated v1 CRD is invalid

[grdryn]

We've got a CRD generated by controller-gen that gets an empty Items object for a list/array in the yaml output. Given that this is a v1 CRD, this results in the CRD not being applicable to a cluster (k8s 1.16+ at least, it seems). It doesn't seem possible to add any markers to influence this, so I'm currently working around it by changing it after generation to have type: object.

Also, I'm not sure if it's related (might be why items is empty?), is that this type is recursive: a Route instance can have a Routes field, which is a []Route.

Here's the type definition that the offending CRD is generated from, and here's how it's generated.

This might be related to the discussion in #342 where @sttts and @DirectXMan12 talk about possibly having :items: markers, but I'm not sure. Maybe at a minimum it should by default be able to add the required type: object for this case (without needing a marker)?

[Wenfeng-GAO]

I meet the same problem, it seems that it doesn't work well for recursive struct definition.

When I apply generated crd to k8s, it prints out

The CustomResourceDefinition "daemonsets.kube-manager.karrier.io" is invalid: spec.validation.openAPIV3Schema.properties[spec].properties[updateStrategy].properties[priorityStrategy].properties[orderPriority].items.properties[orderPriority].items.type: Required value: must not be empty for specified array items

And my struct is recursive list as well:

type PriorityStrategy struct {
	OrderPriority []OrderPriorityItem `json:"orderPriority,omitempty"`
}

type OrderPriorityItem struct {
	Selector      metav1.LabelSelector `json:"selector,omitempty"`
	OrderPriority []OrderPriorityItem  `json:"orderPriority,omitempty"`
}

generated crd is :

                  priorityStrategy:
                    properties:
                      orderPriority:
                        items:
                          properties:
                            orderPriority:
                              items: {}
                              type: array
                            selector:

[DirectXMan12]

Ah. This... could be a clearer error message.

There's no way to have a CRD with recursive types right now, because that would require references, and SIG API Machinery has thus far been reluctant to support references in CRDs.

Specifically, Route --> Routes --> []Route is the recursive issue here.

[DirectXMan12]

I'm going to close this out and file a bug for erroring on recursive types. Feel free to comment there if you have more input

[grdryn]

Thanks @DirectXMan12! 🙂