mesh-issues: carry each value the issues bucket kept, read through the runtime's history, so the log begins with all the bucket still knew (hq ADR 0300 §6, ADR 0307)

modules/mesh-issues/cmd/mesh-issues/bus_test.go

@@ -334,6 +334,26 @@ func (i *instance) answer(m rpc) {
 		case "mesh/state.put":
 			rev, err := kv.Put(ctx, p.Key, p.Value)
 			return map[string]any{"revision": rev}, err
+		case "mesh/state.history":
+			// As the runtime serves it (novox/hq ADR 0307): every value kept, oldest first, puts and deletes.
+			kept, err := kv.History(ctx, p.Key)
+			if errors.Is(err, jetstream.ErrKeyNotFound) {
+				return []any{}, nil
+			}
+			if err != nil {
+				return nil, err
+			}
+			out := []map[string]any{}
+			for _, e := range kept {
+				r := map[string]any{"key": e.Key(), "revision": e.Revision(), "op": "put", "at": e.Created()}
+				if e.Operation() == jetstream.KeyValuePut {
+					r["value"] = json.RawMessage(e.Value())
+				} else {
+					r["op"] = "delete"
+				}
+				out = append(out, r)
+			}
+			return out, nil
 		case "mesh/state.keys":
 			keys, err := kv.Keys(ctx)
 			if errors.Is(err, jetstream.ErrNoKeysFound) {
@@ -566,6 +586,42 @@ func TestFortyReservationsAtOnceFromTwoInstancesGetFortyDistinctConsecutiveNumbe
 	}
 }
 
+// The carry over the bus (novox/hq ADR 0300 §6, ADR 0307): values the bucket kept before the switch are read
+// through the runtime's history, oldest first, and carried before the write that touches the issue.
+func TestAWriteOverTheBusCarriesEveryValueTheBucketKeptFirst(t *testing.T) {
+	b := newBus(t)
+	var events []event
+	var evMu sync.Mutex
+	kv := b.kvs[IssuesState]
+	for _, title := range []string{"first", "second", "third"} {
+		raw, _ := json.Marshal(Issue{Number: 300, Title: title, Status: StatusOpen, Report: "r", OpenedBy: "x", Opening: "o300"})
+		if _, err := kv.Put(context.Background(), "300", raw); err != nil {
+			t.Fatal(err)
+		}
+	}
+	i := b.start(t, writeSettings(t, 365), &events, &evMu)
+	if _, err := i.call("note", map[string]any{"number": 300, "text": "after the switch"}); err != nil {
+		t.Fatal(err)
+	}
+	var titles []string
+	var ops []string
+	for seq := uint64(1); ; seq++ {
+		m, err := b.logs[ChangesLog].GetMsg(context.Background(), seq)
+		if err != nil {
+			break
+		}
+		var op Operation
+		_ = json.Unmarshal(m.Data, &op)
+		ops = append(ops, op.Op)
+		if op.Issue != nil {
+			titles = append(titles, op.Issue.Title)
+		}
+	}
+	if fmt.Sprint(ops) != "[carried carried carried noted]" || fmt.Sprint(titles) != "[first second third]" {
+		t.Fatalf("the log holds %v of %v", ops, titles)
+	}
+}
+
 // One instance, every verb over the bus: what an agent does with an issue from opening to resolving.
 func TestAnIssueIsOpenedNotedLinkedMovedAndListedOverTheBus(t *testing.T) {
 	b := newBus(t)