✨ +enum validation marker

pkg/crd/markers/crd.go

@@ -399,6 +399,12 @@ type SelectableField struct {
 	JSONPath string `marker:"JSONPath"`
 }
 
+// +controllertools:marker:generateHelp:category="CRD validation"
+
+// Enum marker marks a string alias type as an enum.
+// It infers the members from constants declared of that type.
+type InferredEnum struct{}
+
 func (s SelectableField) ApplyToCRD(crd *apiext.CustomResourceDefinitionSpec, version string) error {
 	var selectableFields *[]apiext.SelectableField
 	for i := range crd.Versions {

pkg/crd/markers/validation.go

@@ -113,6 +113,8 @@ var ValidationIshMarkers = []*definitionWithHelp{
 		WithHelp(XPreserveUnknownFields{}.Help()),
 	must(markers.MakeDefinition("kubebuilder:pruning:PreserveUnknownFields", markers.DescribesType, XPreserveUnknownFields{})).
 		WithHelp(XPreserveUnknownFields{}.Help()),
+	must(markers.MakeDefinition("enum", markers.DescribesType, InferredEnum{})).
+		WithHelp(InferredEnum{}.Help()),
 }
 
 func init() {

pkg/crd/parser.go

@@ -18,6 +18,7 @@ package crd
 
 import (
 	"fmt"
+	"go/ast"
 
 	apiext "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
 	"k8s.io/apimachinery/pkg/runtime/schema"
@@ -122,6 +123,21 @@ func (p *Parser) init() {
 	}
 }
 
+func (p *Parser) indexEnumMemberConstantDeclarations(pkg *loader.Package) {
+	loader.EachConstDecl(pkg, func(spec *ast.ValueSpec) {
+		if id, ok := spec.Type.(*ast.Ident); ok {
+			if typeinfo, ok := p.Types[TypeIdent{
+				pkg, id.Name,
+			}]; ok {
+				typeinfo.EnumValues = append(typeinfo.EnumValues, markers.EnumMemberInfo{
+					Name:      spec.Names[0].Name,
+					ValueSpec: spec,
+				})
+			}
+		}
+	})
+}
+
 // indexTypes loads all types in the package into Types.
 func (p *Parser) indexTypes(pkg *loader.Package) {
 	// autodetect
@@ -220,6 +236,7 @@ func (p *Parser) AddPackage(pkg *loader.Package) {
 		return
 	}
 	p.indexTypes(pkg)
+	p.indexEnumMemberConstantDeclarations(pkg)
 	p.Checker.Check(pkg)
 	p.packages[pkg] = struct{}{}
 }

pkg/crd/schema.go

@@ -17,12 +17,14 @@ limitations under the License.
 package crd
 
 import (
+	"encoding/json"
 	"errors"
 	"fmt"
 	"go/ast"
 	"go/token"
 	"go/types"
 	"sort"
+	"strconv"
 	"strings"
 
 	apiext "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
@@ -274,6 +276,29 @@ func localNamedToSchema(ctx *schemaContext, ident *ast.Ident) *apiext.JSONSchema
 		if err != nil {
 			ctx.pkg.AddError(loader.ErrFromNode(err, ident))
 		}
+		var enumMembers []apiext.JSON
+		if ctx.info.Markers.Get("enum") != nil && typ == "string" {
+			enumMembers = make([]apiext.JSON, 0, len(ctx.info.EnumValues))
+			var ok bool
+			for i := range ctx.info.EnumValues {
+				var member = &ctx.info.EnumValues[i]
+				var v *ast.BasicLit
+				if v, ok = member.Values[0].(*ast.BasicLit); !ok {
+					ctx.pkg.AddError(loader.ErrFromNode(errors.New("constants for a +enum decorated type should be stirngs"), ident))
+				}
+				var value string
+				if value, err = strconv.Unquote(v.Value); err != nil {
+					ctx.pkg.AddError(loader.ErrFromNode(err, ident))
+					continue
+				}
+				var j apiext.JSON
+				if j.Raw, err = json.Marshal(value); err != nil {
+					ctx.pkg.AddError(loader.ErrFromNode(err, ident))
+					continue
+				}
+				enumMembers = append(enumMembers, j)
+			}
+		}
 		// Check for type aliasing to a basic type for gotypesalias=0. See more
 		// in documentation https://pkg.go.dev/go/types#Alias:
 		// > For gotypesalias=1, alias declarations produce an Alias type.
@@ -284,12 +309,14 @@ func localNamedToSchema(ctx *schemaContext, ident *ast.Ident) *apiext.JSONSchema
 			link := TypeRefLink("", ident.Name)
 			return &apiext.JSONSchemaProps{
 				Type:   typ,
+				Enum:   enumMembers,
 				Format: fmt,
 				Ref:    &link,
 			}
 		}
 		return &apiext.JSONSchemaProps{
 			Type:   typ,
+			Enum:   enumMembers,
 			Format: fmt,
 		}
 	}

pkg/crd/testdata/cronjob_types.go

@@ -42,6 +42,15 @@ import (
 
 const DefaultRefValue = "defaultRefValue"
 
+// +enum
+type EnumType string
+
+const (
+	EnumType_One   EnumType = "one"
+	EnumType_Two   EnumType = "two"
+	EnumType_Three EnumType = "three"
+)
+
 // CronJobSpec defines the desired state of CronJob
 // +kubebuilder:validation:XValidation:rule="has(oldSelf.forbiddenInt) || !has(self.forbiddenInt)",message="forbiddenInt is not allowed",fieldPath=".forbiddenInt",reason="FieldValueForbidden"
 type CronJobSpec struct {
@@ -332,6 +341,8 @@ type CronJobSpec struct {
 	// +kubebuilder:validation:items:Enum=0;1;3
 	EnumSlice []int `json:"enumSlice,omitempty"`
 
+	EnumValue EnumType `json:"enumValue,omitempty"`
+
 	HostsAlias Hosts `json:"hostsAlias,omitempty"`
 
 	// This tests that alias imported from a package is handled correctly. The