From 1b3db48db7afc3fe17440af28cdeac67a0d048f1 Mon Sep 17 00:00:00 2001
From: Damien Neil <dneil@google.com>
Date: Mon, 22 Dec 2025 16:35:42 -0800
Subject: Revert "errors: optimize errors.Join for single unwrappable errors"

This reverts CL 635115.

Reason for revert: The new behavior does not match the function documentation.

Fixes #76961

Change-Id: If2450aa4efba28c7a12887a5b306c231a836e740
Reviewed-on: https://go-review.googlesource.com/c/go/+/731981
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
---
 src/errors/join_test.go | 34 ----------------------------------
 1 file changed, 34 deletions(-)

(limited to 'src/errors/join_test.go')

diff --git a/src/errors/join_test.go b/src/errors/join_test.go
index 439b372ca0..4828dc4d75 100644
--- a/src/errors/join_test.go
+++ b/src/errors/join_test.go
@@ -70,37 +70,3 @@ func TestJoinErrorMethod(t *testing.T) {
 		}
 	}
 }
-
-func BenchmarkJoin(b *testing.B) {
-	for _, bb := range []struct {
-		name string
-		errs []error
-	}{
-		{
-			name: "no error",
-		},
-		{
-			name: "single non-nil error",
-			errs: []error{errors.New("err")},
-		},
-		{
-			name: "multiple errors",
-			errs: []error{errors.New("err"), errors.New("newerr"), errors.New("newerr2")},
-		},
-		{
-			name: "unwrappable single error",
-			errs: []error{errors.Join(errors.New("err"))},
-		},
-		{
-			name: "nil first error",
-			errs: []error{nil, errors.New("newerr")},
-		},
-	} {
-		b.Run(bb.name, func(b *testing.B) {
-			b.ReportAllocs()
-			for i := 0; i < b.N; i++ {
-				_ = errors.Join(bb.errs...)
-			}
-		})
-	}
-}
-- 
cgit v1.3


From 3faf988f217f59630509c057f48549f59a02c25e Mon Sep 17 00:00:00 2001
From: Damien Neil <dneil@google.com>
Date: Tue, 23 Dec 2025 09:42:37 -0800
Subject: errors: add a test verifying join does not flatten errors

For #76961

Change-Id: Ib81f3202074bf83a5b204b32706445f051f837a8
Reviewed-on: https://go-review.googlesource.com/c/go/+/732360
Auto-Submit: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Sean Liao <sean@liao.dev>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
---
 src/errors/join_test.go | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'src/errors/join_test.go')

diff --git a/src/errors/join_test.go b/src/errors/join_test.go
index 4828dc4d75..8ee4d7f77b 100644
--- a/src/errors/join_test.go
+++ b/src/errors/join_test.go
@@ -25,6 +25,7 @@ func TestJoinReturnsNil(t *testing.T) {
 func TestJoin(t *testing.T) {
 	err1 := errors.New("err1")
 	err2 := errors.New("err2")
+	merr := multiErr{errors.New("err3")}
 	for _, test := range []struct {
 		errs []error
 		want []error
@@ -37,6 +38,9 @@ func TestJoin(t *testing.T) {
 	}, {
 		errs: []error{err1, nil, err2},
 		want: []error{err1, err2},
+	}, {
+		errs: []error{merr},
+		want: []error{merr},
 	}} {
 		got := errors.Join(test.errs...).(interface{ Unwrap() []error }).Unwrap()
 		if !reflect.DeepEqual(got, test.want) {
-- 
cgit v1.3