In the API types, optional structs should be pointers.

[vaikas]

Some API fields are optional, but they should then be pointers as per:
https://github.com/kubernetes/community/blob/master/contributors/devel/sig-architecture/api-conventions.md#optional-vs-required

Expected Behavior

There's couple of structs in the APIs that are marked as optional, but they are not pointers. This means that they get filled in as empties and that causes validation errors.
https://github.com/kedacore/keda/blob/v2/api/v1alpha1/triggerauthentication_types.go#L25
https://github.com/kedacore/keda/blob/v2/api/v1alpha1/triggerauthentication_types.go#L34

And that I could then define (simplified example):

		Spec: kedav1alpha1.TriggerAuthenticationSpec{
			SecretTargetRef: []kedav1alpha1.AuthSecretTargetRef{
				{
					Parameter: "host",
					Name:      secretName,
					Key:       secretKey,
				},
			},

Actual Behavior

However, unless I add this here, it will not pass because the webhook will fail it.

		Spec: kedav1alpha1.TriggerAuthenticationSpec{
			SecretTargetRef: []kedav1alpha1.AuthSecretTargetRef{
				{
					Parameter: "host",
					Name:      secretName,
					Key:       secretKey,
				},
			},
			// HACK. Without this doesn't work.
			HashiCorpVault: kedav1alpha1.HashiCorpVault{Secrets: []kedav1alpha1.VaultSecret{}},

Steps to Reproduce the Problem

1. Call the API with that object, webhook will fail it saying that VaultSecret is null
2. But, now I'm then left with these kinds of log messages:

2020-09-17T18:50:07.737Z	ERROR	scalehandler	Error authenticate to Vault	{"type": "ScaledObject", "namespace": "default", "name": "ping-trigger", "triggerAuthRef.Name": "default-trigger-auth", "error": "Vault auth method  is not supported"}
github.com/go-logr/zapr.(*zapLogger).Error
	/go/pkg/mod/github.com/go-logr/zapr@v0.1.1/zapr.go:128
github.com/kedacore/keda/pkg/scaling/resolver.ResolveAuthRef
	/workspace/pkg/scaling/resolver/scale_resolvers.go:74
github.com/kedacore/keda/pkg/scaling.(*scaleHandler).buildScalers
	/workspace/pkg/scaling/scale_handler.go:306
github.com/kedacore/keda/pkg/scaling.(*scaleHandler).GetScalers
	/workspace/pkg/scaling/scale_handler.go:67
github.com/kedacore/keda/pkg/scaling.(*scaleHandler).checkScalers
	/workspace/pkg/scaling/scale_handler.go:182
github.com/kedacore/keda/pkg/scaling.(*scaleHandler).startScaleLoop
	/workspace/pkg/scaling/scale_handler.go:134

But at least I can now create the resource :)
3.

Specifications

• KEDA Version: V2 Head
• Platform & Version: Please elaborate
• Kubernetes Version: Please elaborate
• Scaler(s): Please elaborate

[zroubalik]

@vaikas good catch, we should convert those structs to the pointers. We have changed the API for v2 anyway, so it won't be a problem.

[vaikas]

/assign
I can do this.