From c20ee283552b9fafff2d089e1846b74ac0b44b85 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Olivier=20Mengu=C3=A9?= <dolmen@cpan.org>
Date: Thu, 21 Mar 2024 01:14:41 +0100
Subject: [PATCH] Walk: add support for go1.20 multi errors (Unwrap() []error)

---
 errwrap.go | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/errwrap.go b/errwrap.go
index 44e368e..a56744e 100644
--- a/errwrap.go
+++ b/errwrap.go
@@ -21,6 +21,9 @@ type WalkFunc func(error)
 // wrapped error in addition to the wrapper itself. Since all the top-level
 // functions in errwrap use Walk, this means that all those functions work
 // with your custom type.
+//
+// Note: since Go 1.20 wrappers should instead implement Unwrap() []error
+// as documented in package [errors] and [errors.Join].
 type Wrapper interface {
 	WrappedErrors() []error
 }
@@ -150,9 +153,15 @@ func Walk(err error, cb WalkFunc) {
 		for _, err := range e.WrappedErrors() {
 			Walk(err, cb)
 		}
-	case interface{ Unwrap() error }:
+	case interface{ Unwrap() error }: // Go 1.13
 		cb(err)
 		Walk(e.Unwrap(), cb)
+	case interface{ Unwrap() []error }: // Go 1.20
+		cb(err)
+
+		for _, err := range e.Unwrap() {
+			Walk(err, cb)
+		}
 	default:
 		cb(err)
 	}