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",
+}
+}