From 70e453b4361b80a85e6ebb37e4d43ec02db9a50a Mon Sep 17 00:00:00 2001
From: Sean Liao <sean@liao.dev>
Date: Tue, 9 Jul 2024 20:24:34 +0100
Subject: [PATCH] context: handle nil values for valueCtx.String()

Fixes #68356

Change-Id: I57dc089a99f545e29a6759a8db5e28fabb6d1a61
Reviewed-on: https://go-review.googlesource.com/c/go/+/597415
Commit-Queue: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Joseph Tsai <joetsai@digital-static.net>
Reviewed-by: Damien Neil <dneil@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
---
 src/context/context.go | 2 ++
 src/context/x_test.go  | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/src/context/context.go b/src/context/context.go
index 30adfe987d..763d4f777f 100644
--- a/src/context/context.go
+++ b/src/context/context.go
@@ -739,6 +739,8 @@ func stringify(v any) string {
 		return s.String()
 	case string:
 		return s
+	case nil:
+		return "<nil>"
 	}
 	return reflectlite.TypeOf(v).String()
 }
diff --git a/src/context/x_test.go b/src/context/x_test.go
index 2c66ed42b2..ab3c2757cf 100644
--- a/src/context/x_test.go
+++ b/src/context/x_test.go
@@ -243,6 +243,10 @@ func TestValues(t *testing.T) {
 	c4 := WithValue(c3, k1, nil)
 	check(c4, "c4", "", "c2k2", "c3k3")
 
+	if got, want := fmt.Sprint(c4), `context.Background.WithValue(context_test.key1, c1k1).WithValue(context_test.key2(1), c2k2).WithValue(context_test.key2(3), c3k3).WithValue(context_test.key1, <nil>)`; got != want {
+		t.Errorf("c.String() = %q want %q", got, want)
+	}
+
 	o0 := otherContext{Background()}
 	check(o0, "o0", "", "", "")
 
-- 
2.48.1