fixup! Add support for struct tag name overrides in native types

ext/native.go

@@ -86,10 +86,10 @@ var (
 // ```go
 // package identity
 //
-//		type Account struct {
-//		  ID int
-//	   OwnerName string `cel:"owner"`
-//		}
+//	type Account struct {
+//	  ID int
+//	  OwnerName string `cel:"owner"`
+//	}
 //
 // ```
 //
@@ -125,6 +125,7 @@ func NativeTypes(args ...any) cel.EnvOption {
 	}
 }
 
+// NativeTypesOption is a functional interface for configuring handling of native types.
 type NativeTypesOption func(*nativeTypeOptions) error
 
 type nativeTypeOptions struct {
@@ -133,6 +134,7 @@ type nativeTypeOptions struct {
 	parseStructTags bool
 }
 
+// ParseStructTags configures if native types field names should be overridable by CEL struct tags.
 func ParseStructTags(enabled bool) NativeTypesOption {
 	return func(ntp *nativeTypeOptions) error {
 		ntp.parseStructTags = true
@@ -597,18 +599,23 @@ func newNativeType(parseStructTags bool, rawType reflect.Type) (*nativeType, err
 	if !isValidObjectType(refType) {
 		return nil, fmt.Errorf("unsupported reflect.Type %v, must be reflect.Struct", rawType)
 	}
-	fieldNames := make(map[string]struct{})
 
-	for idx := 0; idx < refType.NumField(); idx++ {
-		field := refType.Field(idx)
-		fieldName := toFieldName(parseStructTags, field)
+	// Since naming collisions can only happen with struct tag parsing, we only check for them if it is enabled.
+	if parseStructTags {
+		fieldNames := make(map[string]struct{})
+
+		for idx := 0; idx < refType.NumField(); idx++ {
+			field := refType.Field(idx)
+			fieldName := toFieldName(parseStructTags, field)
 
-		if _, found := fieldNames[fieldName]; found {
-			return nil, fmt.Errorf("invalid field name `%s` in struct `%s`: %w", fieldName, refType.Name(), errDuplicatedFieldName)
-		} else {
-			fieldNames[fieldName] = struct{}{}
+			if _, found := fieldNames[fieldName]; found {
+				return nil, fmt.Errorf("invalid field name `%s` in struct `%s`: %w", fieldName, refType.Name(), errDuplicatedFieldName)
+			} else {
+				fieldNames[fieldName] = struct{}{}
+			}
 		}
 	}
+
 	return &nativeType{
 		typeName:        fmt.Sprintf("%s.%s", simplePkgAlias(refType.PkgPath()), refType.Name()),
 		refType:         refType,
@@ -670,6 +677,10 @@ func (t *nativeType) Value() any {
 // fieldByName returns the corresponding reflect.StructField for the give name either by matching
 // field tag or field name.
 func (t *nativeType) fieldByName(fieldName string) (reflect.StructField, bool) {
+	if !t.parseStructTags {
+		return t.refType.FieldByName(fieldName)
+	}
+
 	for i := 0; i < t.refType.NumField(); i++ {
 		f := t.refType.Field(i)
 		if toFieldName(t.parseStructTags, f) == fieldName {