Add deprecated warnings

experimental/deprecated/env.go

@@ -0,0 +1,30 @@
+package deprecated
+
+import (
+	"os"
+	"strconv"
+
+	"github.com/sagernet/sing/common/logger"
+)
+
+type envManager struct {
+	logger logger.Logger
+}
+
+func NewEnvManager(logger logger.Logger) Manager {
+	return &envManager{logger: logger}
+}
+
+func (f *envManager) ReportDeprecated(feature Note) {
+	if !feature.Impending() {
+		f.logger.Warn(feature.MessageWithLink())
+		return
+	}
+	enable, enableErr := strconv.ParseBool(os.Getenv("ENABLE_DEPRECATED_" + feature.EnvName))
+	if enableErr == nil && enable {
+		f.logger.Warn(feature.MessageWithLink())
+		return
+	}
+	f.logger.Error(feature.MessageWithLink())
+	f.logger.Fatal("to continuing using this feature, set ENABLE_DEPRECATED_" + feature.EnvName + "=true")
+}