msghub: Clear deleted messages instead of unlinking (#348)

Signed-off-by: James Hillyerd <james@hillyerd.com>

pkg/msghub/hub_test.go

@@ -9,6 +9,8 @@ import (
 
 	"github.com/inbucket/inbucket/pkg/extension"
 	"github.com/inbucket/inbucket/pkg/extension/event"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 // testListener implements the Listener interface, mock for unit tests
@@ -302,6 +304,59 @@ func TestHubHistoryReplayWrap(t *testing.T) {
 	}
 }
 
+func TestHubHistoryReplayWrapAfterDelete(t *testing.T) {
+	bufferSize := 5
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	hub := New(bufferSize, extension.NewHost())
+	go hub.Start(ctx)
+
+	waitForMessages := func(n int) {
+		l := newTestListener(n)
+		hub.AddListener(l)
+
+		select {
+		case <-l.done:
+		case <-time.After(time.Second):
+			t.Fatal("Timeout:", l)
+		}
+	}
+
+	// Broadcast more messages than the hub can hold.
+	msgs := make([]event.MessageMetadata, 10)
+	for i := 0; i < len(msgs); i++ {
+		msgs[i] = event.MessageMetadata{
+			Mailbox: "first",
+			ID:      strconv.Itoa(i),
+			Subject: fmt.Sprintf("subj %v", i),
+		}
+		hub.Dispatch(msgs[i])
+	}
+	waitForMessages(bufferSize)
+
+	// Buffer must be configured size.
+	require.Equal(t, bufferSize, hub.history.Len())
+
+	// Delete a message still present in buffer.
+	hub.Delete("first", "7")
+
+	// Broadcast another set of messages.
+	for i := 0; i < len(msgs); i++ {
+		msgs[i] = event.MessageMetadata{
+			Mailbox: "second",
+			ID:      strconv.Itoa(i),
+			Subject: fmt.Sprintf("subj %v", i),
+		}
+		hub.Dispatch(msgs[i])
+	}
+	waitForMessages(bufferSize)
+
+	// Ensure the buffer did not shrink after delete.
+	got := hub.history.Len()
+	assert.Equal(t, bufferSize, got, "got buffer size %d, wanted %d", got, bufferSize)
+}
+
 func TestHubContextCancel(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
 	hub := New(5, extension.NewHost())