Never wait NextMsg's bound for a dead letter held already overcounts (issue 728)

internal/link/deadletters_restricted_test.go

@@ -218,3 +218,34 @@ func TestTheAgingOfRestrictedDeadLettersIsRead(t *testing.T) {
 		t.Fatalf("aging %+v, kept %+v", aging, d)
 	}
 }
+
+// **A look never waits out NextMsg's bound for a dead letter that is not there** (novox/hq issue 728 review round
+// 1): held can count more than DEAD_LETTERS still holds for a consumer, one aged out, delivered again or dropped
+// since it was counted. AgingDeadLetters reads the ordered consumer's pending count once and looks for at most
+// that many, so it returns in well under the 2-second NextMsg bound rather than waiting it out for messages that
+// are gone.
+func TestTheAgingOfRestrictedDeadLettersDoesNotWaitForWhatHeldOvercounts(t *testing.T) {
+	js := aBus(t)
+	subject := aRestrictedStream(t, js)
+	seq, published := publishMail(t, js, subject)
+	withClock(t, func() time.Time { return published.Add(time.Hour) })
+	d, err := KeepDeadLetter(js.Context(), notice(seq))
+	if err != nil {
+		t.Fatal(err)
+	}
+	// held says 3 for this consumer; DEAD_LETTERS holds only the one just kept.
+	held := map[string]int{"MAIL.ace_mailer": 3}
+
+	started := time.Now()
+	aging, err := AgingDeadLetters(js.Context(), held)
+	elapsed := time.Since(started)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if elapsed >= time.Second {
+		t.Fatalf("took %s, well over the 2-second bound it should never wait out", elapsed)
+	}
+	if len(aging["MAIL.ace_mailer"]) != 1 || aging["MAIL.ace_mailer"][0].ID != d.ID {
+		t.Fatalf("aging %+v, kept %+v", aging, d)
+	}
+}