feat(crd): Add k8s:required and k8s:optional markers

This commit introduces `k8s:required` and `k8s:optional` markers to align with the declarative validation KEP. These markers serve as a Kubernetes-style alternative to the existing `+required` and `+optional` markers for marking CRD fields.

This change allows controller-gen to better understand native types in CRDs, improving the declarative validation process.

Reference: https://github.com/kubernetes/enhancements/blob/master/keps/sig-api-machinery/5073-declarative-validation-with-validation-gen/README.md

Author: lalitc375

pkg/crd/markers/validation.go

@@ -97,7 +97,10 @@ var FieldOnlyMarkers = []*definitionWithHelp{
 		WithHelp(markers.SimpleHelp("CRD validation", "specifies that this field is required.")),
 	must(markers.MakeDefinition("optional", markers.DescribesField, struct{}{})).
 		WithHelp(markers.SimpleHelp("CRD validation", "specifies that this field is optional.")),
-
+	must(markers.MakeDefinition("k8s:required", markers.DescribesField, struct{}{})).
+		WithHelp(markers.SimpleHelp("CRD validation", "specifies that this field is required.")),
+	must(markers.MakeDefinition("k8s:optional", markers.DescribesField, struct{}{})).
+		WithHelp(markers.SimpleHelp("CRD validation", "specifies that this field is optional.")),
 	must(markers.MakeDefinition("nullable", markers.DescribesField, Nullable{})).
 		WithHelp(Nullable{}.Help()),
 

pkg/crd/schema.go

@@ -469,16 +469,15 @@ func structToSchema(ctx *schemaContext, structType *ast.StructType) *apiext.JSON
 			}
 			// explicitly required - kubebuilder
 			props.Required = append(props.Required, fieldName)
-		case field.Markers.Get("optional") != nil:
-			// explicitly optional - kubernetes
-		case field.Markers.Get("required") != nil:
+		case field.Markers.Get("optional") != nil, field.Markers.Get("k8s:optional") != nil:
+			// explicitly optional
+		case field.Markers.Get("required") != nil, field.Markers.Get("k8s:required") != nil:
 			if exactlyOneOf.Has(fieldName) || atMostOneOf.Has(fieldName) {
 				ctx.pkg.AddError(loader.ErrFromNode(fmt.Errorf("field %s is part of OneOf constraint and cannot be marked as required", fieldName), structType))
 				return props
 			}
-			// explicitly required - kubernetes
+			// explicitly required
 			props.Required = append(props.Required, fieldName)
-
 		// if this package isn't set to optional default...
 		case defaultMode == "required":
 			// ...everything that's not inline / omitempty is required

pkg/crd/testdata/cronjob_types.go

@@ -238,6 +238,10 @@ type CronJobSpec struct {
 	// +optional
 	ExplicitlyOptionalKubernetes string `json:"explicitlyOptionalKubernetes"`
 
+	// This tests explicitly optional k8s fields
+	// +k8s:optional
+	ExplicitlyOptionalK8s string `json:"explicitlyOptionalK8s"`
+
 	// This tests explicitly required kubebuilder fields
 	// +kubebuilder:validation:Required
 	ExplicitlyRequiredKubebuilder string `json:"explicitlyRequiredKubebuilder,omitempty"`
@@ -246,6 +250,10 @@ type CronJobSpec struct {
 	// +required
 	ExplicitlyRequiredKubernetes string `json:"explicitlyRequiredKubernetes,omitempty"`
 
+	// This tests explicitly required k8s fields
+	// +k8s:required
+	ExplicitlyRequiredK8s string `json:"explicitlyRequiredK8s,omitempty"`
+
 	// This tests that min/max properties work
 	MinMaxProperties MinMaxObject `json:"minMaxProperties,omitempty"`
 

pkg/crd/testdata/testdata.kubebuilder.io_cronjobs.yaml

@@ -201,12 +201,18 @@ spec:
                   - 3
                   type: integer
                 type: array
+              explicitlyOptionalK8s:
+                description: This tests explicitly optional k8s fields
+                type: string
               explicitlyOptionalKubebuilder:
                 description: This tests explicitly optional kubebuilder fields
                 type: string
               explicitlyOptionalKubernetes:
                 description: This tests explicitly optional kubernetes fields
                 type: string
+              explicitlyRequiredK8s:
+                description: This tests explicitly required k8s fields
+                type: string
               explicitlyRequiredKubebuilder:
                 description: This tests explicitly required kubebuilder fields
                 type: string
@@ -9137,6 +9143,7 @@ spec:
             - defaultedString
             - doubleDefaultedString
             - embeddedResource
+            - explicitlyRequiredK8s
             - explicitlyRequiredKubebuilder
             - explicitlyRequiredKubernetes
             - float64WithValidations