refs #815 Added CJsonException and related utilities.

src/blackmisc/jsonexception.cpp

@@ -0,0 +1,58 @@
+/* Copyright (C) 2016
+ * swift project Community / Contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
+ * including this file, may be copied, modified, propagated, or distributed except according to the terms
+ * contained in the LICENSE file.
+ */
+
+#include "blackmisc/jsonexception.h"
+#include "blackmisc/statusmessage.h"
+#include "blackmisc/logcategorylist.h"
+#include "blackmisc/logmessage.h"
+#include <QStringBuilder>
+#include <QThreadStorage>
+#include <vector>
+
+namespace BlackMisc
+{
+    //! \private
+    auto &jsonStack() noexcept
+    {
+        static QThreadStorage<std::vector<const CJsonScope *>> stack;
+        return stack.localData();
+    }
+
+    CStatusMessage CJsonException::toStatusMessage(const CLogCategoryList &categories, const QString &prefix) const
+    {
+        return CStatusMessage(categories).validationError("%1: %2 in '%3'") << prefix << what() << getStackTrace();
+    }
+
+    void CJsonException::toLogMessage(const CLogCategoryList &categories, const QString &prefix) const
+    {
+        CLogMessage(categories).validationError("%1: %2 in '%3'") << prefix << what() << getStackTrace();
+    }
+
+    QString CJsonException::stackString()
+    {
+        QStringList list;
+        for (const auto scope : BlackMisc::as_const(jsonStack()))
+        {
+            list.push_back(scope->m_string ? *scope->m_string : scope->m_latin1);
+            if (scope->m_index >= 0) { list.back() += "[" % QString::number(scope->m_index) % "]"; }
+        }
+        return list.isEmpty() ? QStringLiteral("<document root>") : list.join('.');
+    }
+
+    void CJsonScope::push() const noexcept
+    {
+        jsonStack().push_back(this);
+    }
+
+    void CJsonScope::pop() const noexcept
+    {
+        Q_ASSERT(jsonStack().back() == this);
+        jsonStack().pop_back();
+    }
+}

src/blackmisc/jsonexception.h

@@ -0,0 +1,87 @@
+/* Copyright (C) 2016
+ * swift project Community / Contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
+ * including this file, may be copied, modified, propagated, or distributed except according to the terms
+ * contained in the LICENSE file.
+ */
+
+//! \file
+
+#ifndef BLACKMISC_JSONEXCEPTION_H
+#define BLACKMISC_JSONEXCEPTION_H
+
+#include "blackmisc/blackmiscexport.h"
+#include <QString>
+#include <stdexcept>
+
+namespace BlackMisc
+{
+    class CStatusMessage;
+    class CLogCategoryList;
+
+    /*!
+     * Thrown when a convertFromJson method encounters an unrecoverable error in JSON data.
+     */
+    class BLACKMISC_EXPORT CJsonException : public std::runtime_error
+    {
+    public:
+        //! Constructor.
+        explicit CJsonException(const QString &message) : std::runtime_error(message.toStdString()) {}
+
+        //! Get a stack trace of where in the JSON object tree the error occurred.
+        const QString &getStackTrace() const { return m_stack; }
+
+        //! Get a status message representation.
+        CStatusMessage toStatusMessage(const CLogCategoryList &categories, const QString &prefix) const;
+
+        //! Write a message to the log.
+        void toLogMessage(const CLogCategoryList &categories, const QString &prefix) const;
+
+    private:
+        static QString stackString();
+
+        QString m_stack = stackString();
+    };
+
+    /*!
+     * Pseudo-RAII pattern that tracks the current JSON value being converted.
+     *
+     * Will be used to construct a stack trace for CJsonException::getStackTrace.
+     * Class is optimized to introduce minimal overhead in the unexceptional case.
+     */
+    class BLACKMISC_EXPORT CJsonScope
+    {
+    public:
+        //! Construct a scope with the given name and optional index subscript.
+        //! @{
+        CJsonScope(const QString &name, int index = -1) noexcept : m_index(index), m_string(&name) { push(); }
+        CJsonScope(QLatin1String name, int index = -1) noexcept : m_index(index), m_latin1(name) { push(); }
+        template <size_t N> CJsonScope(const char (&name)[N], int index = -1) noexcept : CJsonScope(QLatin1String(name, N), index) {}
+        //! @}
+
+        //! QString constructor argument must be an lvalue.
+        CJsonScope(const QString &&, int = -1) = delete;
+
+        //! Not copyable.
+        //! @{
+        CJsonScope(const CJsonScope &) = delete;
+        CJsonScope &operator =(const CJsonScope &) = delete;
+        //! @}
+
+        //! Destructor.
+        ~CJsonScope() { pop(); }
+
+    private:
+        void push() const noexcept;
+        void pop() const noexcept;
+
+        friend class CJsonException;
+        int m_index = -1;
+        const QString *m_string = nullptr;
+        QLatin1String m_latin1;
+    };
+}
+
+#endif