feat: Add resource field scoped fields

pkg/crd/markers/crd.go

@@ -55,6 +55,9 @@ var CRDMarkers = []*definitionWithHelp{
 
 	must(markers.MakeDefinition("kubebuilder:metadata", markers.DescribesType, Metadata{})).
 		WithHelp(Metadata{}.Help()),
+
+	must(markers.MakeDefinition("kubebuilder:field:scope", markers.DescribesField, FieldScope(""))).
+		WithHelp(FieldScope("").Help()),
 }
 
 // TODO: categories and singular used to be annotations types
@@ -388,3 +391,12 @@ func (s Metadata) ApplyToCRD(crd *apiext.CustomResourceDefinition, _ string) err
 
 	return nil
 }
+
+// +controllertools:marker:generateHelp:category=CRD
+// FieldScope specifies the scope of the field. If the field scope does not match the outer-most
+// resource scope, then this field is ignored and not included in the final CRD.
+type FieldScope string
+
+func (m FieldScope) Value() string {
+	return string(m)
+}

pkg/crd/schema.go

@@ -22,6 +22,7 @@ import (
 	"go/ast"
 	"go/token"
 	"go/types"
+	"reflect"
 	"sort"
 	"strings"
 
@@ -333,6 +334,11 @@ func mapToSchema(ctx *schemaContext, mapType *ast.MapType) *apiext.JSONSchemaPro
 	}
 }
 
+// fieldScopePropertyName is the name of the property used to sore field scope information. A more
+// appropriate solution would be to use a custom extension, but that's not possible yet.
+// See: https://github.com/kubernetes/kubernetes/issues/82942
+const fieldScopePropertyName = "x-kubebuilder-field-scopes"
+
 // structToSchema creates a schema for the given struct.  Embedded fields are placed in AllOf,
 // and can be flattened later with a Flattener.
 func structToSchema(ctx *schemaContext, structType *ast.StructType) *apiext.JSONSchemaProps {
@@ -346,6 +352,7 @@ func structToSchema(ctx *schemaContext, structType *ast.StructType) *apiext.JSON
 		return props
 	}
 
+	var clusterScopedFields, namespaceScopedFields []string
 	for _, field := range ctx.info.Fields {
 		// Skip if the field is not an inline field, ignoreUnexportedFields is true, and the field is not exported
 		if field.Name != "" && ctx.ignoreUnexportedFields && !ast.IsExported(field.Name) {
@@ -377,6 +384,30 @@ func structToSchema(ctx *schemaContext, structType *ast.StructType) *apiext.JSON
 		fieldName := jsonOpts[0]
 		inline = inline || fieldName == "" // anonymous fields are inline fields in YAML/JSON
 
+		if scope := field.Markers.Get("kubebuilder:field:scope"); scope != nil {
+			value, ok := scope.(crdmarkers.FieldScope)
+			if !ok {
+				ctx.pkg.AddError(loader.ErrFromNode(fmt.Errorf("encountered non-string struct %q field %q scope %s", ctx.info.Name, field.Name, reflect.ValueOf(scope).Type().Name()), field.RawField))
+				continue
+			}
+			var scope apiext.ResourceScope
+			switch value {
+			case "":
+				scope = apiext.NamespaceScoped
+			default:
+				scope = apiext.ResourceScope(value)
+			}
+			switch scope {
+			case apiext.ClusterScoped:
+				clusterScopedFields = append(clusterScopedFields, fieldName)
+			case apiext.NamespaceScoped:
+				namespaceScopedFields = append(namespaceScopedFields, fieldName)
+			default:
+				ctx.pkg.AddError(loader.ErrFromNode(fmt.Errorf("invalid struct %q field %q scope %q", ctx.info.Name, field.Name, value), field.RawField))
+				continue
+			}
+		}
+
 		// if no default required mode is set, default to required
 		defaultMode := "required"
 		if ctx.PackageMarkers.Get("kubebuilder:validation:Optional") != nil {
@@ -417,6 +448,22 @@ func structToSchema(ctx *schemaContext, structType *ast.StructType) *apiext.JSON
 		props.Properties[fieldName] = *propSchema
 	}
 
+	if len(clusterScopedFields) > 0 || len(namespaceScopedFields) > 0 {
+		props.Properties[fieldScopePropertyName] = apiext.JSONSchemaProps{
+			Type: "object",
+			Properties: map[string]apiext.JSONSchemaProps{
+				string(apiext.ClusterScoped): {
+					Type:     "object",
+					Required: clusterScopedFields,
+				},
+				string(apiext.NamespaceScoped): {
+					Type:     "object",
+					Required: namespaceScopedFields,
+				},
+			},
+		}
+	}
+
 	return props
 }
 

pkg/crd/spec.go

@@ -17,6 +17,7 @@ package crd
 
 import (
 	"fmt"
+	"slices"
 	"sort"
 	"strings"
 
@@ -104,6 +105,7 @@ func (p *Parser) NeedCRDFor(groupKind schema.GroupKind, maxDescLen *int) {
 			},
 		}
 		crd.Spec.Versions = append(crd.Spec.Versions, ver)
+
 	}
 
 	// markers are applied *after* initial generation of objects
@@ -130,6 +132,15 @@ func (p *Parser) NeedCRDFor(groupKind schema.GroupKind, maxDescLen *int) {
 		}
 	}
 
+	// Apply field-scoped resources. The markers live on the field, not in the top-level CRD, so we
+	// must apply them manually here.
+	for versionIndex := range crd.Spec.Versions {
+		version := &crd.Spec.Versions[versionIndex]
+		if err := applyFieldScopes(version.Schema.OpenAPIV3Schema, crd.Spec.Scope); err != nil {
+			packages[0].AddError(fmt.Errorf("CRD for %s was unable to apply field scopes", groupKind))
+		}
+	}
+
 	// fix the name if the plural was changed (this is the form the name *has* to take, so no harm in changing it).
 	crd.Name = crd.Spec.Names.Plural + "." + groupKind.Group
 
@@ -176,3 +187,38 @@ func (p *Parser) NeedCRDFor(groupKind schema.GroupKind, maxDescLen *int) {
 
 	p.CustomResourceDefinitions[groupKind] = crd
 }
+
+func applyFieldScopes(props *apiext.JSONSchemaProps, scope apiext.ResourceScope) error {
+	var removed string
+	if scope == apiext.NamespaceScoped {
+		removed = string(apiext.ClusterScoped)
+	} else if scope == apiext.ClusterScoped {
+		removed = string(apiext.NamespaceScoped)
+	}
+	if err := removeScope(props, removed); err != nil {
+		return err
+	}
+	return nil
+}
+
+func removeScope(props *apiext.JSONSchemaProps, scope string) error {
+	scopes, ok := props.Properties[fieldScopePropertyName]
+	if ok {
+		for _, item := range scopes.Properties[scope].Required {
+			delete(props.Properties, item)
+
+			index := slices.Index(props.Required, item)
+			if index == -1 {
+				continue
+			}
+			props.Required = slices.Delete(props.Required, index, index+1)
+		}
+	}
+	delete(props.Properties, fieldScopePropertyName)
+
+	for name, p := range props.Properties {
+		removeScope(&p, scope)
+		props.Properties[name] = p
+	}
+	return nil
+}