Add QXmppError holding a description and std::any

2 files changed, 126 insertions, 0 deletions

diff --git a/src/base/QXmppError.cpp b/src/base/QXmppError.cpp
new file mode 100644
index 00000000..80578c0d
--- /dev/null
+++ b/src/base/QXmppError.cpp
@@ -0,0 +1,75 @@
+// SPDX-FileCopyrightText: 2022 Linus Jahn <lnj@kaidan.im>
+//
+// SPDX-License-Identifier: LGPL-2.1-or-later
+
+#include "QXmppError.h"
+
+#include "QXmppStanza.h"
+
+#include <QFileDevice>
+#include <QNetworkReply>
+
+///
+/// \class QXmppError
+///
+/// Generic error class holding a description and a more specific error object. The specific error
+/// usually is something like a QXmppStanza::Error or an enum.
+///
+/// \since QXmpp 1.5
+///
+
+///
+/// \var QXmppError::description
+///
+/// Human readable description of the error.
+///
+
+///
+/// \var QXmppError::error
+///
+/// More specific details on the error. It may be of any type. Functions returning QXmppError
+/// should tell you which types are used.
+///
+
+///
+/// Returns whether the error is a QNetworkReply::NetworkError.
+///
+bool QXmppError::isFileError() const
+{
+    return holdsType<QFileDevice::FileError>();
+}
+
+///
+/// Returns whether the error is a QNetworkReply::NetworkError.
+///
+bool QXmppError::isNetworkError() const
+{
+    return holdsType<QNetworkReply::NetworkError>();
+}
+
+///
+/// Returns whether the error is a QXmppStanza::Error.
+///
+bool QXmppError::isStanzaError() const
+{
+    return holdsType<QXmppStanza::Error>();
+}
+
+///
+/// \fn QXmppError::holdsType()
+///
+/// Returns true if the error is of type T.
+///
+
+///
+/// \fn QXmppError::value()
+///
+/// Copies the value if it has type T, returns empty optional otherwise.
+///
+
+///
+/// \fn QXmppError::takeValue()
+///
+/// Moves out the value if it has type T, leaves the stored error intact and returns an empty
+/// optional otherwise.
+///
diff --git a/src/base/QXmppError.h b/src/base/QXmppError.h
new file mode 100644
index 00000000..a646b6e5
--- /dev/null
+++ b/src/base/QXmppError.h
@@ -0,0 +1,51 @@
+// SPDX-FileCopyrightText: 2022 Linus Jahn <lnj@kaidan.im>
+//
+// SPDX-License-Identifier: LGPL-2.1-or-later
+
+#ifndef QXMPPERROR_H
+#define QXMPPERROR_H
+
+#include "QXmppGlobal.h"
+
+#include <any>
+#include <optional>
+
+struct QXMPP_EXPORT QXmppError
+{
+    QString description;
+    std::any error;
+
+    bool isFileError() const;
+    bool isNetworkError() const;
+    bool isStanzaError() const;
+
+    template<typename T>
+    bool holdsType() const
+    {
+        return error.type().hash_code() == typeid(T).hash_code();
+    }
+    template<typename T>
+    std::optional<T> value() const
+    {
+        // any_cast always checks this, to avoid an additional check we use exceptions
+        try {
+            return std::any_cast<T>(error);
+        } catch (std::bad_any_cast) {
+            return {};
+        }
+    }
+    template<typename T>
+    std::optional<T> takeValue()
+    {
+        // we can't use unchecked any_cast with moving because we can't access the error after a
+        // failed any_cast
+        if (error.type().hash_code() == typeid(T).hash_code()) {
+            auto value = std::any_cast<T>(std::move(error));
+            error = std::any();
+            return value;
+        }
+        return {};
+    }
+};
+
+#endif  // QXMPPERROR_H