feat: Expose methods to query ErrNoSuchMessage / ErrNoSuchMailbox

errors.go

@@ -0,0 +1,18 @@
+// Package gluon implements an IMAP4rev1 (+ extensions) mailserver.
+package gluon
+
+import (
+	"errors"
+
+	"github.com/ProtonMail/gluon/internal/state"
+)
+
+// IsNoSuchMessage returns true if the error is ErrNoSuchMessage.
+func IsNoSuchMessage(err error) bool {
+	return errors.Is(err, state.ErrNoSuchMessage)
+}
+
+// IsNoSuchMailbox returns true if the error is ErrNoSuchMailbox.
+func IsNoSuchMailbox(err error) bool {
+	return errors.Is(err, state.ErrNoSuchMailbox)
+}