imapmemserver: implement minimal NOTIFY support

This is just enough support to add round-trip tests for the basic
portion.

Author: WhyNotHugo

imapclient/client_test.go

@@ -102,6 +102,7 @@ func newMemClientServerPair(t *testing.T) (net.Conn, io.Closer) {
 		Caps: imap.CapSet{
 			imap.CapIMAP4rev1: {},
 			imap.CapIMAP4rev2: {},
+			imap.CapNotify:    {},
 		},
 	})
 

imapclient/notify_test.go

@@ -0,0 +1,112 @@
+package imapclient_test
+
+import (
+	"testing"
+
+	"github.com/emersion/go-imap/v2"
+)
+
+func TestClient_Notify(t *testing.T) {
+	client, server := newClientServerPair(t, imap.ConnStateAuthenticated)
+	defer client.Close()
+	defer server.Close()
+
+	// Test NOTIFY with SELECTED mailbox
+	options := &imap.NotifyOptions{
+		Items: []imap.NotifyItem{
+			{
+				MailboxSpec: imap.NotifyMailboxSpecSelected,
+				Events: []imap.NotifyEvent{
+					imap.NotifyEventMessageNew,
+					imap.NotifyEventMessageExpunge,
+				},
+			},
+		},
+	}
+
+	// Note: The test server's stub implementation refuses NOTIFY with
+	// NO [NOTIFICATIONOVERFLOW], which is RFC-compliant per RFC 5465 Section 3.1.
+	_, err := client.Notify(options)
+	if err == nil {
+		t.Fatal("Expected error from stub implementation")
+	}
+
+	imapErr, ok := err.(*imap.Error)
+	if !ok {
+		t.Fatalf("Expected *imap.Error, got %T", err)
+	}
+	if imapErr.Type != imap.StatusResponseTypeNo {
+		t.Errorf("Expected NO response, got %v", imapErr.Type)
+	}
+	if imapErr.Code != imap.ResponseCodeNotificationOverflow {
+		t.Errorf("Expected NOTIFICATIONOVERFLOW code, got %v", imapErr.Code)
+	}
+}
+
+func TestClient_NotifyNone(t *testing.T) {
+	client, server := newClientServerPair(t, imap.ConnStateAuthenticated)
+	defer client.Close()
+	defer server.Close()
+
+	// Note: The test server's stub implementation refuses NOTIFY with
+	// NO [NOTIFICATIONOVERFLOW]
+	err := client.NotifyNone()
+	if err == nil {
+		t.Fatal("Expected error from stub implementation")
+	}
+	imapErr, ok := err.(*imap.Error)
+	if !ok {
+		t.Fatalf("Expected *imap.Error, got %T", err)
+	}
+	if imapErr.Type != imap.StatusResponseTypeNo {
+		t.Errorf("Expected NO response, got %v", imapErr.Type)
+	}
+	if imapErr.Code != imap.ResponseCodeNotificationOverflow {
+		t.Errorf("Expected NOTIFICATIONOVERFLOW code, got %v", imapErr.Code)
+	}
+}
+
+func TestClient_NotifyMultiple(t *testing.T) {
+	client, server := newClientServerPair(t, imap.ConnStateAuthenticated)
+	defer client.Close()
+	defer server.Close()
+
+	// Test NOTIFY with multiple items
+	options := &imap.NotifyOptions{
+		STATUS: true,
+		Items: []imap.NotifyItem{
+			{
+				MailboxSpec: imap.NotifyMailboxSpecSelected,
+				Events: []imap.NotifyEvent{
+					imap.NotifyEventMessageNew,
+					imap.NotifyEventMessageExpunge,
+				},
+			},
+			{
+				MailboxSpec: imap.NotifyMailboxSpecPersonal,
+				Events: []imap.NotifyEvent{
+					imap.NotifyEventMailboxName,
+					imap.NotifyEventSubscriptionChange,
+				},
+			},
+		},
+	}
+
+	// Note: The test server's stub implementation refuses NOTIFY with
+	// NO [NOTIFICATIONOVERFLOW]
+	_, err := client.Notify(options)
+	if err == nil {
+		t.Fatal("Expected error from stub implementation")
+	}
+
+	imapErr, ok := err.(*imap.Error)
+	if !ok {
+		t.Fatalf("Expected *imap.Error, got %T", err)
+	}
+	if imapErr.Type != imap.StatusResponseTypeNo {
+		t.Errorf("Expected NO response, got %v", imapErr.Type)
+	}
+	if imapErr.Code != imap.ResponseCodeNotificationOverflow {
+		t.Errorf("Expected NOTIFICATIONOVERFLOW code, got %v", imapErr.Code)
+	}
+}

imapserver/imapmemserver/session.go

@@ -138,3 +138,20 @@ func (sess *UserSession) Idle(w *imapserver.UpdateWriter, stop <-chan struct{})
 	}
 	return sess.mailbox.Idle(w, stop)
 }
+
+func (sess *UserSession) Notify(w *imapserver.UpdateWriter, options *imap.NotifyOptions) error {
+	// Refuse the NOTIFY request with NO [NOTIFICATIONOVERFLOW] to indicate
+	// the server is unable/unwilling to deliver notifications.
+	//
+	// Per RFC 5465 Section 3.1 (lines 327-330):
+	// "If the notification would be prohibitively expensive for the server
+	// (e.g., "notify me of all flag changes in all mailboxes"), the server
+	// MAY refuse the command with a tagged NO [NOTIFICATIONOVERFLOW] response."
+	//
+	// This is a simple RFC-compliant stub. Implementing full NOTIFY support is pending.
+	return &imap.Error{
+		Type: imap.StatusResponseTypeNo,
+		Code: imap.ResponseCodeNotificationOverflow,
+		Text: "Request not implemented",
+	}
+}