From 46c93951d0d5823aa11eae4c9f3db7a531345857 Mon Sep 17 00:00:00 2001
From: Yanhu007 <huangfuyang900204@gmail.com>
Date: Wed, 15 Apr 2026 03:36:36 +0800
Subject: [PATCH] fix: return nil from Decorate and EnhanceStackTrace when err
 is nil

Decorate(nil, ...) previously created a synthetic.foreign error with
no useful type information. This is surprising and makes it
impossible to use Decorate in error-forwarding patterns like:

  return errorx.Decorate(maybeNilErr, "context")

Now both Decorate and EnhanceStackTrace return nil when given a nil
error, consistent with the Go convention that wrapping nil returns nil.

Fixes #40
---
 wrap.go | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/wrap.go b/wrap.go
index eb929db..5d1097e 100644
--- a/wrap.go
+++ b/wrap.go
@@ -19,6 +19,9 @@ var (
 // Without args, leaves the provided message intact, so a message may be generated or provided externally.
 // With args, a formatting is performed, and it is therefore expected a format string to be constant.
 func Decorate(err error, message string, args ...interface{}) *Error {
+	if err == nil {
+		return nil
+	}
 	return NewErrorBuilder(transparentWrapper).
 		WithConditionallyFormattedMessage(message, args...).
 		WithCause(err).
@@ -30,6 +33,9 @@ func Decorate(err error, message string, args ...interface{}) *Error {
 // Designed to be used when a original error is passed from another goroutine rather than from a direct method call.
 // If, however, it is called in the same goroutine, formatter makes some moderated effort to remove duplication.
 func EnhanceStackTrace(err error, message string, args ...interface{}) *Error {
+	if err == nil {
+		return nil
+	}
 	return NewErrorBuilder(transparentWrapper).
 		WithConditionallyFormattedMessage(message, args...).
 		WithCause(err).