Use url.URL type with controller-gen (kubernetes-operator)

example_types.go

// api/v1/example_types.go
// link to the post : https://stackoverflow.com/questions/72097153/use-url-url-with-controller-gen

// A part of an example CRD
package v1

import (
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"

  	"{path_of_your_module}/internal/url"
)

// ExampleSpec defines the desired state of Example
type ExampleSpec struct {
  	// In order to validate the url as a string use the marker Type=string
	// +kubebuilder:validation:Type=string
	// +kubebuilder:validation:MinLength=42
	Url *url.URL `json:"url,omitempty"`
}

//+kubebuilder:object:root=true
//+kubebuilder:subresource:status

// Example is the Schema for the Examples API
type Example struct {
	metav1.TypeMeta   `json:",inline"`
	metav1.ObjectMeta `json:"metadata,omitempty"`

	Spec   ExampleSpec   `json:"spec,omitempty"`
	Status ExampleStatus `json:"status,omitempty"`
}

// ExampleStatus defines the observed state of Example
type ExampleStatus struct {
  [...]
}

url.go

// internal/url/url.go
// link to the post : https://stackoverflow.com/questions/72097153/use-url-url-with-controller-gen
package url

import (
	"encoding/json"
	"fmt"
	"net/url"
)

// URL wraps url.URL.
// It has custom json marshal methods that enable it to be used in K8s CRDs
// such that the CRD resource will have the URL but operator code can can work with url.URL struct
type URL struct {
	url.URL
}

func (u *URL) MarshalJSON() ([]byte, error) {
	return []byte(fmt.Sprintf("%q", u.String())), nil
}

func (u *URL) UnmarshalJSON(b []byte) error {
	var ref string
	if err := json.Unmarshal(b, &ref); err != nil {
		return err
	}
	if ref == "" {
		*u = URL{}
		return nil
	}

	r, err := url.Parse(ref)
	if err != nil {
		return err
	} else if r != nil {
		*u = URL{*r}
	} else {
		*u = URL{}
	}
	return nil
}

func (u *URL) String() string {
	if u == nil {
		return ""
	}
	return u.URL.String()
}

// DeepCopyInto copy the receiver, write into out. in must be non-nil.
func (in *URL) DeepCopyInto(out *URL) {
	*out = *in
}

// DeepCopy copy the receiver, create a new URL.
func (in *URL) DeepCopy() *URL {
	if in == nil {
		return nil
	}
	out := new(URL)
	in.DeepCopyInto(out)
	return out
}