function

package main

import (
	"fmt"

	"google.golang.org/protobuf/encoding/protojson"

	"github.com/crossplane/function-sdk-go/proto/v1beta1"
	"github.com/crossplane/function-sdk-go/request"
	"github.com/crossplane/function-sdk-go/resource"
	"github.com/crossplane/function-sdk-go/resource/composed"
	"github.com/crossplane/function-sdk-go/response"
)

var req = &v1beta1.RunFunctionRequest{
	Observed: &v1beta1.State{
		Composite: &v1beta1.Resource{
			Resource: resource.MustStructJSON(`{"spec":{"widgets":9001}}`),
		},
	},
}

func main() {
	// Create a response to the request passed to your RunFunction method.
	rsp := response.To(req, response.DefaultTTL)

	// Get the observed composite resource (XR) from the request.
	oxr, _ := request.GetObservedCompositeResource(req)

	// Read the desired number of widgets from our observed XR.
	widgets, _ := oxr.Resource.GetInteger("spec.widgets")

	// Get any existing desired composed resources from the request.
	// Desired composed resources would exist if a previous Function in the
	// pipeline added them.
	desired, _ := request.GetDesiredComposedResources(req)

	// Create a desired composed resource using unstructured data.
	desired["new"] = &resource.DesiredComposed{Resource: composed.New()}
	desired["new"].Resource.SetAPIVersion("example.org/v1")
	desired["new"].Resource.SetKind("CoolResource")

	// Set the desired composed resource's widgets to the value extracted from
	// the observed XR.
	desired["new"].Resource.SetInteger("spec.widgets", widgets)

	// Create a desired composed resource using structured data.
	// db, _ := composed.From(&v1beta1.Instance{})
	// desired["database"] = &resource.DesiredComposed{Resource: db}

	// Add a label to our new desired resource, and any other.
	for _, r := range desired {
		r.Resource.SetLabels(map[string]string{"coolness": "high"})
	}

	// Set our updated desired composed resource in the response we'll return.
	_ = response.SetDesiredComposedResources(rsp, desired)

	j, _ := protojson.Marshal(rsp)
	fmt.Println(string(j))

}

Output:

{"meta":{"ttl":"60s"},"desired":{"resources":{"new":{"resource":{"apiVersion":"example.org/v1","kind":"CoolResource","metadata":{"labels":{"coolness":"high"}},"spec":{"widgets":9001}}}}}}