Dynamically find `PodSpec` in manifests

[MPV]

Currently kir has hardcoded instructions of which kinds it supports and where inside each's structure that the PodSpec could be found:

kir/k8s/k8s.go

Lines 11 to 31 in 26fef45

	// GetPodSpec extracts the PodSpec from a Kubernetes object
	func GetPodSpec(obj interface{}) (*corev1.PodSpec, error) {
	switch resource := obj.(type) {
	case *corev1.Pod:
	return &resource.Spec, nil
	case *appsv1.Deployment:
	return &resource.Spec.Template.Spec, nil
	case *appsv1.DaemonSet:
	return &resource.Spec.Template.Spec, nil
	case *appsv1.ReplicaSet:
	return &resource.Spec.Template.Spec, nil
	case *appsv1.StatefulSet:
	return &resource.Spec.Template.Spec, nil
	case *batchv1.Job:
	return &resource.Spec.Template.Spec, nil
	case *batchv1.CronJob:
	return &resource.Spec.JobTemplate.Spec.Template.Spec, nil
	default:
	return nil, fmt.Errorf("object does not have a PodSpec")
	}
	}

I'm imagining that it could be possible to "look for the PodSpec" in the YAML, and when it matches, extract the images from there.

Possible benefits could be:

• Less hardcoded kinds/structures.
• Easier to use with other (custom) resources that include a PodSpec.

Possible drawbacks:

• Slower.
• Easier to get wrong.
• More brittle.

[MPV]

One method for doing this could be using Cue, I’ll look into making a PR for this, to see how it fares.

Paul and I hacked together something here at Kubecon London:

• https://github.com/myitcvscratch/yamlpodspec