From 0be0ffd6159e7efac1a6a5bc0740bca4f35fecce Mon Sep 17 00:00:00 2001
From: jochen <jschoubben@gmail.com>
Date: Sun, 25 Oct 2026 21:47:30 +0100
Subject: [PATCH] =?UTF-8?q?Compare=20the=20have's=20user=20list=20by=20wha?=
 =?UTF-8?q?t=20it=20says,=20so=20a=20have=20is=20not=20written=20again=20f?=
 =?UTF-8?q?or=20the=20same=20list=20(ADR=200547=20=C2=A78)?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 go/delivery/delivery.go      | 14 +++++++++++++-
 go/delivery/delivery_test.go | 12 ++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/go/delivery/delivery.go b/go/delivery/delivery.go
index 769420c..8fccfaa 100644
--- a/go/delivery/delivery.go
+++ b/go/delivery/delivery.go
@@ -491,7 +491,19 @@ func DecodePulse(data []byte) (Pulse, error) {
 }
 
 // SameHave says whether two haves are the same value, so a writer writes only when they differ.
-func SameHave(a, b Have) bool { return a == b }
+func SameHave(a, b Have) bool {
+	ua, ub := a.UserList, b.UserList
+	a.UserList, b.UserList = nil, nil
+	if a != b || (ua == nil) != (ub == nil) {
+		return false
+	}
+	if ua == nil {
+		return true
+	}
+	x, y := *ua, *ub
+	x.At, y.At = time.Time{}, time.Time{}
+	return x == y && ua.At.Equal(ub.At)
+}
 
 // SameHaveNode says whether two node facts are the same value, comparing each carried JSON without its spacing.
 func SameHaveNode(a, b HaveNode) bool {
diff --git a/go/delivery/delivery_test.go b/go/delivery/delivery_test.go
index 3b1ac09..a0aba8d 100644
--- a/go/delivery/delivery_test.go
+++ b/go/delivery/delivery_test.go
@@ -294,6 +294,18 @@ func TestSame(t *testing.T) {
 	if SameHave(a, b) {
 		t.Error("different haves same")
 	}
+	// The user list is compared by what it says, never by where it is held (ADR 0547 §8).
+	at := time.Date(2026, 10, 25, 21, 0, 0, 0, time.UTC)
+	ua, ub := a, a
+	ua.UserList = &UserListWritten{Source: "k", Revision: 1, Wanted: "sha256:a", Digest: "sha256:a", Users: 2, At: at}
+	ub.UserList = &UserListWritten{Source: "k", Revision: 1, Wanted: "sha256:a", Digest: "sha256:a", Users: 2, At: at.In(time.Local)}
+	if !SameHave(ua, ub) || SameHave(ua, a) {
+		t.Error("equal user lists differ, or one said and one not are the same")
+	}
+	ub.UserList.Revision = 2
+	if SameHave(ua, ub) {
+		t.Error("different user lists same")
+	}
 	n := HaveNode{V: 1, Busy: json.RawMessage(`true`)}
 	if !SameHaveNode(n, HaveNode{V: 1, Busy: json.RawMessage(`true`)}) || SameHaveNode(n, HaveNode{V: 1}) {
 		t.Error("have node")