Merge pull request #72 from Icinga/reflectPtr

config/: enforce type constraints via generics, not reflection

config/config.go

@@ -8,7 +8,6 @@ import (
 	"github.com/jessevdk/go-flags"
 	"github.com/pkg/errors"
 	"os"
-	"reflect"
 )
 
 // ErrInvalidArgument is the error returned by [ParseFlags] or [FromYAMLFile] if
@@ -19,10 +18,9 @@ var ErrInvalidArgument = stderrors.New("invalid argument")
 // FromYAMLFile parses the given YAML file and stores the result
 // in the value pointed to by v. If v is nil or not a pointer,
 // FromYAMLFile returns an [ErrInvalidArgument] error.
-func FromYAMLFile(name string, v Validator) error {
-	rv := reflect.ValueOf(v)
-	if rv.Kind() != reflect.Pointer || rv.IsNil() {
-		return errors.Wrapf(ErrInvalidArgument, "non-nil pointer expected, got %T", v)
+func FromYAMLFile[T any, V validatorPtr[T]](name string, v V) error {
+	if v == nil {
+		return errors.Wrap(ErrInvalidArgument, "got nil pointer")
 	}
 
 	// #nosec G304 -- Potential file inclusion via variable - Its purpose is to load any file name that is passed to it, so doesn't need to validate anything.
@@ -59,10 +57,9 @@ func FromYAMLFile(name string, v Validator) error {
 // ParseFlags prints the help message to [os.Stdout] and exits.
 // Note that errors are not printed automatically,
 // so error handling is the sole responsibility of the caller.
-func ParseFlags(v any) error {
-	rv := reflect.ValueOf(v)
-	if rv.Kind() != reflect.Pointer || rv.IsNil() {
-		return errors.Wrapf(ErrInvalidArgument, "non-nil pointer expected, got %T", v)
+func ParseFlags[T any](v *T) error {
+	if v == nil {
+		return errors.Wrap(ErrInvalidArgument, "got nil pointer")
 	}
 
 	parser := flags.NewParser(v, flags.Default^flags.PrintErrors)

config/contracts.go

@@ -3,3 +3,9 @@ package config
 type Validator interface {
 	Validate() error
 }
+
+// validatorPtr combines the [Validator] interface with a pointer constraint.
+type validatorPtr[T any] interface {
+	Validator
+	*T
+}