From 3b49e512c4e40994a4e8fdc77cd005a71974696e Mon Sep 17 00:00:00 2001
From: Eric Lippmann <eric.lippmann@icinga.com>
Date: Mon, 21 Oct 2024 10:12:42 +0200
Subject: [PATCH] Revert "Merge pull request #72 from Icinga/reflectPtr"

This reverts commit f25f8a03e301395f9bf3873783970f8e502479a7, reversing
changes made to a2fd4d4fc03652d0871e4800eeb2f2b005d6f08b.

While the changes relax the necessary checks for passing a valid pointer, they
complicate the tests and still allow non-construct pointer types that implement
the validator interface to pass. This negates the benefits, making it simpler
to validate the pointer argument in a function as previously done.
---
 config/config.go    | 15 +++++++++------
 config/contracts.go |  6 ------
 2 files changed, 9 insertions(+), 12 deletions(-)

diff --git a/config/config.go b/config/config.go
index bccf1fa6..df998a82 100644
--- a/config/config.go
+++ b/config/config.go
@@ -8,6 +8,7 @@ import (
 	"github.com/jessevdk/go-flags"
 	"github.com/pkg/errors"
 	"os"
+	"reflect"
 )
 
 // ErrInvalidArgument is the error returned by [ParseFlags] or [FromYAMLFile] if
@@ -18,9 +19,10 @@ 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[T any, V validatorPtr[T]](name string, v V) error {
-	if v == nil {
-		return errors.Wrap(ErrInvalidArgument, "got nil pointer")
+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)
 	}
 
 	// #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.
@@ -57,9 +59,10 @@ func FromYAMLFile[T any, V validatorPtr[T]](name string, v V) 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[T any](v *T) error {
-	if v == nil {
-		return errors.Wrap(ErrInvalidArgument, "got nil pointer")
+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)
 	}
 
 	parser := flags.NewParser(v, flags.Default^flags.PrintErrors)
diff --git a/config/contracts.go b/config/contracts.go
index 288a8f3a..76022991 100644
--- a/config/contracts.go
+++ b/config/contracts.go
@@ -3,9 +3,3 @@ package config
 type Validator interface {
 	Validate() error
 }
-
-// validatorPtr combines the [Validator] interface with a pointer constraint.
-type validatorPtr[T any] interface {
-	Validator
-	*T
-}