feat: load explicit configuration references and remove implicit env overlays

config/loader.go

@@ -26,6 +26,7 @@ func (f DecoderFunc) Decode(data []byte) (Document, error) { return f(data) }
 type Loader struct {
 	decoders map[string]Decoder
 	sealed   bool
+	lookup   func(string) (string, bool)
 }
 type LoaderOption func(*Loader) error
 
@@ -55,7 +56,7 @@ func WithDecoder(extension string, decoder Decoder) LoaderOption {
 }
 
 func NewLoader(options ...LoaderOption) (*Loader, error) {
-	l := &Loader{decoders: map[string]Decoder{"json": JSONDecoder{}, "yaml": YAMLDecoder{}, "yml": YAMLDecoder{}, "xml": XMLDecoder{}}}
+	l := &Loader{lookup: os.LookupEnv, decoders: map[string]Decoder{"json": JSONDecoder{}, "yaml": YAMLDecoder{}, "yml": YAMLDecoder{}, "xml": XMLDecoder{}}}
 	for _, o := range options {
 		if o == nil {
 			return nil, errors.New("config: nil loader option")
@@ -135,7 +136,7 @@ func (l *Loader) read(path string) (doc Document, err error) {
 	if _, ok := doc.Value.(map[string]any); !ok {
 		return doc, doc.diagnostic("", "root must be an object", nil)
 	}
-	return doc, nil
+	return resolveDocument(doc, l.lookup)
 }
 func decodeSafely(decoder Decoder, data []byte) (doc Document, err error) {
 	defer func() {
@@ -165,11 +166,12 @@ func DecodeFile[T any](path string, defaults T, loaders ...*Loader) (T, error) {
 	if err != nil {
 		return zero, err
 	}
+	if err := rejectEnvironmentTags(reflect.TypeOf(defaults), map[reflect.Type]bool{}); err != nil {
+		return zero, err
+	}
 	result, err := bindDocument(doc, defaults)
 	if err != nil {
-		d := validationError(err)
-		d.File = path
-		return zero, d
+		return zero, locateError(err, path, doc)
 	}
 	return result, nil
 }