I'm currently writing a kubernetes controller, using kubernetes go-client.

I've managed to generate the OpenAPI spec for the resources managed by the controller (by running openapi-gen and annotating types with +k8s:openapi-gen=true).

I also want to generate validators like a maximum length or regex but I don't find any resource about how to do it.

Here is my types.go

package v1

import (
    meta "k8s.io/apimachinery/pkg/apis/meta/v1"
)

// +genclient
// +k8s:openapi-gen=true
// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object
// +resource:path=project

type Project struct {
    meta.TypeMeta   `json:",inline"`
    meta.ObjectMeta `json:"metadata,omitempty"`

    Domain string `json:"domain"`
}

// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

type ProjectList struct {
    meta.TypeMeta `json:",inline"`
    meta.ListMeta `json:"metadata,omitempty"`
    Items         []Project `json:"items"`
}

What I'm trying to achieve is to generate the OpenAPI spec using openapi-gen and include in the spec the following validation for the Domain: regex [a-z]+ and maximum length of 18.