[DEMO, do not merge] Generated EnsureReferences output for code-generator#738

[gustavodiaz7722]

Demonstration only — not for merge.

Opened at the request of a reviewer on aws-controllers-k8s/code-generator#738, to show what that PR emits in the context of a full service controller.

lambda-controller regenerated against code-generator#738 with no other change, so the diff is exactly the generated EnsureReferences methods and nothing else. Local build stamps (pkg/version/version.go, ack-generate-metadata.yaml) were reverted deliberately, since they would otherwise show a spurious generator downgrade.

Why lambda

It exercises all three reference shapes, so the per-shape behaviour is visible in one controller:

Resource	Shape	Emitted
function	struct-nested — Code.S3BucketRef, VPCConfig.SecurityGroupRefs, VPCConfig.SubnetRefs	yes
layer_version	struct-nested	yes
event_source_mapping	list-nested	no
alias, code_signing_config, function_url_config, version	top-level only	no

function is the shape reported in aws-controllers-k8s/community#2431.

The generated method

func (rm *resourceManager) EnsureReferences(
	desired acktypes.AWSResource,
	latest acktypes.AWSResource,
) acktypes.AWSResource {
	// Deep copy the source as well, so a reference handed over below does not
	// alias the caller's declared object.
	desiredKO := rm.concreteResource(desired).ko.DeepCopy()
	latestKO := rm.concreteResource(latest).ko.DeepCopy()

	if desiredKO.Spec.Code != nil {
		if desiredKO.Spec.Code.S3BucketRef != nil {
			if latestKO.Spec.Code == nil {
				latestKO.Spec.Code = &svcapitypes.FunctionCode{}
			}
			if latestKO.Spec.Code.S3BucketRef == nil {
				latestKO.Spec.Code.S3BucketRef = desiredKO.Spec.Code.S3BucketRef
			}
		}
	}
	if desiredKO.Spec.VPCConfig != nil {
		if len(desiredKO.Spec.VPCConfig.SecurityGroupRefs) > 0 {
			if latestKO.Spec.VPCConfig == nil {
				latestKO.Spec.VPCConfig = &svcapitypes.VPCConfig{}
			}
			if len(latestKO.Spec.VPCConfig.SecurityGroupRefs) == 0 {
				latestKO.Spec.VPCConfig.SecurityGroupRefs = desiredKO.Spec.VPCConfig.SecurityGroupRefs
			}
		}
	}
	if desiredKO.Spec.VPCConfig != nil {
		if len(desiredKO.Spec.VPCConfig.SubnetRefs) > 0 {
			if latestKO.Spec.VPCConfig == nil {
				latestKO.Spec.VPCConfig = &svcapitypes.VPCConfig{}
			}
			if len(latestKO.Spec.VPCConfig.SubnetRefs) == 0 {
				latestKO.Spec.VPCConfig.SubnetRefs = desiredKO.Spec.VPCConfig.SubnetRefs
			}
		}
	}

	return &resource{latestKO}
}

Each assignment is guarded on the declared resource actually holding a reference and on the target missing it, so it cannot clobber a reference the service did report. The container is constructed on the target when it is absent -- generated set-output code nils it when the response omits it, and without that the reference would be dropped in exactly the case it most needs restoring.

Compatibility

go.mod is unchanged. The method compiles against the current runtime and stays inert until aws-controllers-k8s/runtime#267 lands, which defines the optional ReferenceEnsurer interface and invokes it after Create and after Update.

Relationship to the existing hooks

templates/hooks/function/sdk_create_post_set_output.go.tpl and sdk_read_one_post_set_output.go.tpl currently restore these same references by hand. This PR does not remove either. runtime#267 subsumes the create-path half. The read-path half is left alone, and AdoptionPolicy_Adopt deliberately replaces a declared reference along with the rest of the declared spec.

Related: aws-controllers-k8s/code-generator#738, aws-controllers-k8s/runtime#267, aws-controllers-k8s/community#2431.

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