qmldom: Start of the Qml Dom library

The goal of the Dom library is to provide a nicer to use basis for the
Qml Code model, to be used by the various QML tools, the designer and
the new compiler.

This commit just adds some common utilities used by the library, to
output strings to a Sink, i.e. a function<void(QStringView).
This allows writing without allocations of extra temporary strings.
The more interesting parts are added in subsequent commits

Task-number: QTBUG-74840
Change-Id: I8fa43d5b622f59c8761b2469551127c0508c23c3
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

6 files changed, 572 insertions, 0 deletions

diff --git a/src/qmldom/CMakeLists.txt b/src/qmldom/CMakeLists.txt
new file mode 100644
index 0000000000..2e7134dd40
--- /dev/null
+++ b/src/qmldom/CMakeLists.txt
@@ -0,0 +1,22 @@
+# Generated from qmldom.pro.
+
+#####################################################################
+## QmlCompiler Module:
+#####################################################################
+
+qt_internal_add_module(QmlDom
+    STATIC
+    INTERNAL_MODULE
+    SOURCES
+       qqmldom_global.h
+       qqmldomconstants_p.h
+       qqmldomstringdumper.cpp qqmldomstringdumper_p.h
+    DEFINES
+       QMLDOM_LIBRARY
+    PUBLIC_LIBRARIES
+        Qt::CorePrivate
+        Qt::QmlDevToolsPrivate
+)
+
+#### Keys ignored in scope 1:.:.:qmlcompiler.pro:<TRUE>:
+# _OPTION = "host_build"
diff --git a/src/qmldom/qmldom.pro b/src/qmldom/qmldom.pro
new file mode 100644
index 0000000000..282566cc9d
--- /dev/null
+++ b/src/qmldom/qmldom.pro
@@ -0,0 +1,16 @@
+option(host_build)
+TARGET     = QtQmlDom
+QT         = core-private qmldevtools-private
+CONFIG    += minimal_syncqt internal_module generated_privates
+
+DEFINES += QMLDOM_LIBRARY
+
+SOURCES += \
+    $$PWD/qqmldomstringdumper.cpp
+
+HEADERS += \
+    $$PWD/qqmldom_global.h \
+    $$PWD/qqmldomconstants_p.h \
+    $$PWD/qqmldomstringdumper_p.h
+
+load(qt_module)
diff --git a/src/qmldom/qqmldom_global.h b/src/qmldom/qqmldom_global.h
new file mode 100644
index 0000000000..d76f6efeac
--- /dev/null
+++ b/src/qmldom/qqmldom_global.h
@@ -0,0 +1,57 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQml module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**/
+#ifndef QMLDOM_GLOBAL_H
+#define QMLDOM_GLOBAL_H
+
+#include <QtCore/qglobal.h>
+
+#if defined(QMLDOM_DYNAMIC)
+#if defined(QMLDOM_LIBRARY)
+#  define QMLDOM_EXPORT Q_DECL_EXPORT
+#else
+#  define QMLDOM_EXPORT Q_DECL_IMPORT
+#endif
+#else
+#  define QMLDOM_EXPORT
+#endif
+
+QT_BEGIN_NAMESPACE
+// avoid annoying warning about missing QT_BEGIN_NAMESPACE...
+QT_END_NAMESPACE
+
+#endif // QMLDOM_GLOBAL_H
diff --git a/src/qmldom/qqmldomconstants_p.h b/src/qmldom/qqmldomconstants_p.h
new file mode 100644
index 0000000000..43cbbdda28
--- /dev/null
+++ b/src/qmldom/qqmldomconstants_p.h
@@ -0,0 +1,87 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQml module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**/
+#ifndef QQMLDOMCONSTANTS_P_H
+#define QQMLDOMCONSTANTS_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include "qqmldom_global.h"
+
+#include <QtCore/QObject>
+#include <QtCore/QMetaObject>
+
+QT_BEGIN_NAMESPACE
+
+namespace QQmlJS{
+namespace Dom {
+
+Q_NAMESPACE_EXPORT(QMLDOM_EXPORT)
+
+enum class EscapeOptions{
+    OuterQuotes,
+    NoOuterQuotes
+};
+Q_ENUM_NS(EscapeOptions)
+
+enum class ErrorLevel{
+    Debug,
+    Info,
+    Hint,         // cosmetic or convention
+    MaybeWarning, // possibly a warning, insufficient information
+    Warning,
+    MaybeError,
+    Error,
+    Fatal
+};
+Q_ENUM_NS(ErrorLevel)
+
+} // end namespace Dom
+} // end namespace QQmlJS
+
+QT_END_NAMESPACE
+
+#endif // QQMLDOMCONSTANTS_P_H
diff --git a/src/qmldom/qqmldomstringdumper.cpp b/src/qmldom/qqmldomstringdumper.cpp
new file mode 100644
index 0000000000..1788d79d3d
--- /dev/null
+++ b/src/qmldom/qqmldomstringdumper.cpp
@@ -0,0 +1,238 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQml module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**/
+#include "qqmldomstringdumper_p.h"
+#include <QtCore/QDebug>
+
+QT_BEGIN_NAMESPACE
+
+namespace QQmlJS {
+namespace Dom {
+
+/*!
+ * \internal
+ * \tn QQmlJS::Dom::Sink
+ * \brief A Sink is a function that accepts a QStringView as input
+ *
+ * A Sink it the core element of a text based stream oriented output.
+ * It is simply a function accepting a QStringView as input.
+ */
+
+/*!
+ * \internal
+ * \tn QQmlJS::Dom::sinkInt
+ * \brief writes an integer to a sink without any axtra heap allocation
+ * \param sink where to write
+ * \param i the integer to write out
+ *
+ * mainly for debugging/fatal errors
+ */
+
+/*!
+ * \internal
+ * \class QQmlJS::Dom::Dumper
+ * \brief Helper class to accept eithe a string or a dumper (a function that writes to a sink)
+ *
+ * Using a Dumper as input parameter one always obtains a dumper (i.e. a
+ * std::function<void(std::function<void(QStringView)>)> , but can pass in any
+ * object accepted by QStringView, and it is automatically converted to a dumper.
+ */
+
+/*!
+ * \internal
+ * \brief Converts a dumper to a string
+ * \param writer The dumper convert to a string
+ */
+QString dumperToString(Dumper writer)
+{
+    QString s;
+    QTextStream d(&s);
+    writer([&d](QStringView s){ d << s; });
+    d.flush();
+    return s;
+}
+
+/*!
+ * \internal
+ * \brief dumps a string as quoted string (escaping things like quotes or newlines)
+ * \param sink The sink to write the quoted string to
+ * \param s The string to sink
+ * \param options If quotes should be outputted around the string (defaults to yes)
+ */
+void sinkEscaped(Sink sink, QStringView s, EscapeOptions options) {
+    if (options == EscapeOptions::OuterQuotes)
+        sink(u"\"");
+    int it0=0;
+    for (int it = 0; it < s.length();++it) {
+        QChar c=s[it];
+        bool noslash = c != QLatin1Char('\\');
+        bool noquote = c != QLatin1Char('"');
+        bool nonewline = c != QLatin1Char('\n');
+        bool noreturn = c != QLatin1Char('\r');
+        if (noslash && noquote && nonewline && noreturn)
+            continue;
+        sink(s.mid(it0, it - it0));
+        it0 = it + 1;
+        if (!noslash)
+            sink(u"\\\\");
+        else if (!noquote)
+            sink(u"\\\"");
+        else if (!nonewline)
+            sink(u"\\n");
+        else if (!noreturn)
+            sink(u"\\r");
+        else
+            Q_ASSERT(0);
+    }
+    sink(s.mid(it0, s.length() - it0));
+    if (options == EscapeOptions::OuterQuotes)
+        sink(u"\"");
+}
+
+/*!
+ * \internal
+ * \brief Dumps a string describing the given error level (ErrorLevel::Error -> Error,...)
+ * \param s the sink to write to
+ * \param level the level to describe
+ */
+void dumpErrorLevel(Sink s, ErrorLevel level)
+{
+    switch (level) {
+    case ErrorLevel::Debug:
+        s(u"Debug");
+        break;
+    case ErrorLevel::Info:
+        s(u"Info");
+        break;
+    case ErrorLevel::Hint:
+        s(u"Hint");
+        break;
+    case ErrorLevel::MaybeWarning:
+        s(u"MaybeWarn");
+        break;
+    case ErrorLevel::Warning:
+        s(u"Warning");
+        break;
+    case ErrorLevel::MaybeError:
+        s(u"MaybeErr");
+        break;
+    case ErrorLevel::Error:
+        s(u"Error");
+        break;
+    case ErrorLevel::Fatal:
+        s(u"Fatal");
+        break;
+    }
+
+}
+
+void dumperToQDebug(Dumper dumper, QDebug debug)
+{
+    QDebug & d = debug.noquote().nospace();
+    dumper([&d](QStringView s){
+        d << s;
+    });
+}
+
+/*!
+ * \internal
+ * \brief writes the dumper to the QDebug object corrsponding to the given error level
+ * \param level the error level of the message
+ * \param dumper the dumper that writes a message
+ */
+void dumperToQDebug(Dumper dumper, ErrorLevel level)
+{
+    QDebug d = qDebug().noquote().nospace();
+    switch (level) {
+    case ErrorLevel::Debug:
+        break;
+    case ErrorLevel::Info:
+    case ErrorLevel::Hint:
+        d = qInfo().noquote().nospace();
+        break;
+    case ErrorLevel::MaybeWarning:
+    case ErrorLevel::Warning:
+        d = qWarning().noquote().nospace();
+        break;
+    case ErrorLevel::MaybeError:
+    case ErrorLevel::Error:
+    case ErrorLevel::Fatal: // should be handled differently (avoid allocations...), we try to catch them before ending up here
+        d = qCritical().noquote().nospace();
+        break;
+    }
+    dumper([&d](QStringView s){
+        d << s;
+    });
+}
+
+/*!
+ * \internal
+ * \brief sinks the requested amount of spaces
+ */
+void sinkIndent(Sink s, int indent)
+{
+    if (indent > 0) {
+        QStringView spaces = u"                     ";
+        while (indent > spaces.length()) {
+            s(spaces);
+            indent -= spaces.length();
+        }
+        s(spaces.left(indent));
+    }
+}
+
+/*!
+ * \internal
+ * \brief sinks a neline and indents by the given amount
+ */
+void sinkNewline(Sink s, int indent)
+{
+    s(u"\n");
+    if (indent > 0)
+        sinkIndent(s, indent);
+}
+
+/*!
+ * \internal
+ * \fn QQmlJS::Dom::devNull
+ * \brief A sink that ignores whatever it receives
+ */
+
+} // end namespace Dom
+} // end namespace QQmlJS
+
+QT_END_NAMESPACE
diff --git a/src/qmldom/qqmldomstringdumper_p.h b/src/qmldom/qqmldomstringdumper_p.h
new file mode 100644
index 0000000000..7669bfc882
--- /dev/null
+++ b/src/qmldom/qqmldomstringdumper_p.h
@@ -0,0 +1,152 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQml module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**/
+#ifndef DUMPER_H
+#define DUMPER_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include "qqmldom_global.h"
+#include "qqmldomconstants_p.h"
+
+#include <QtCore/QString>
+#include <QtCore/QStringView>
+#include <QtCore/QDebug>
+
+#include <type_traits>
+
+QT_BEGIN_NAMESPACE
+
+namespace QQmlJS {
+namespace Dom {
+
+using Sink = std::function<void(QStringView)>;
+using DumperFunction = std::function<void(Sink)>;
+
+class Dumper{
+public:
+    DumperFunction dumper;
+private:
+    // We want to avoid the limit of one user conversion:
+    // after doing (* -> QStringView) we cannot have QStringView -> Dumper, as it
+    // would be the second user defined conversion.
+    // For a similar reason we have a template to accept function<void(Sink)> .
+    // The end result is that void f(Dumper) can be called nicely, and avoid overloads:
+    // f(u"bla"), f(QLatin1String("bla")), f(QString()), f([](Sink s){...}),...
+    template <typename T>
+    using if_compatible_dumper = typename
+    std::enable_if<std::is_convertible<T, DumperFunction>::value, bool>::type;
+
+    template<typename T>
+    using if_string_view_convertible = typename
+    std::enable_if<std::is_convertible_v<T, QStringView>, bool>::type;
+
+public:
+    Dumper(QStringView s):
+        dumper([s](Sink sink){ sink(s); }) {}
+
+    Dumper(std::nullptr_t): Dumper(QStringView(nullptr)) {}
+
+    template <typename Stringy, if_string_view_convertible<Stringy> = true>
+    Dumper(Stringy string):
+        Dumper(QStringView(string)) {}
+
+    template <typename U, if_compatible_dumper<U> = true>
+    Dumper(U f): dumper(f) {}
+
+    void operator()(Sink s) { dumper(s); }
+};
+
+template <typename T>
+void sinkInt(Sink s, T i) {
+    const int BUFSIZE = 42; // safe up to 128 bits
+    QChar buf[BUFSIZE];
+    int ibuf = BUFSIZE;
+    buf[--ibuf] = QChar(0);
+    bool neg = false;
+    if (i < 0)
+        neg=true;
+    int digit = i % 10;
+    i = i / 10;
+    if constexpr (std::is_signed_v<T>) {
+        if (neg) { // we change the sign here because -numeric_limits<T>::min() == numeric_limits<T>::min()
+            i = -i;
+            digit = - digit;
+        }
+    }
+    buf[--ibuf] = QChar::fromLatin1('0' + digit);
+    while (i > 0 && ibuf > 0) {
+        digit = i % 10;
+        buf[--ibuf] = QChar::fromLatin1('0' + digit);
+        i = i / 10;
+    }
+    if (neg && ibuf > 0)
+        buf[--ibuf] = QChar::fromLatin1('-');
+    s(QStringView(&buf[ibuf], BUFSIZE - ibuf -1));
+}
+
+QMLDOM_EXPORT QString dumperToString(Dumper writer);
+
+QMLDOM_EXPORT void sinkEscaped(Sink sink, QStringView s,
+                               EscapeOptions options = EscapeOptions::OuterQuotes);
+
+inline void devNull(QStringView) {}
+
+QMLDOM_EXPORT void sinkIndent(Sink s, int indent);
+
+QMLDOM_EXPORT void sinkNewline(Sink s, int indent = 0);
+
+QMLDOM_EXPORT void dumpErrorLevel(Sink s, ErrorLevel level);
+
+QMLDOM_EXPORT void dumperToQDebug(Dumper dumper, QDebug debug);
+
+QMLDOM_EXPORT void dumperToQDebug(Dumper dumper, ErrorLevel level = ErrorLevel::Debug);
+
+} // end namespace Dom
+} // end namespace QQmlJS
+QT_END_NAMESPACE
+
+#endif // DUMPER_H