Meson: Flatten directory hierarchy

Keep tests/ and icons/ but put the rest into the toplevel.

The previous setup was so different from the rest of the bunch that
it regularly stuck out in maintenance tasks.

Change-Id: I69821be6268f69682353a388f6bb1fa343215303
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/plugins/mesonprojectmanager/buildsystemfilesparser.h

@@ -0,0 +1,59 @@
+// Copyright (C) 2020 Alexis Jeandet.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0+ OR GPL-3.0 WITH Qt-GPL-exception-1.0
+
+#pragma once
+
+#include "common.h"
+#include "mesonpluginconstants.h"
+
+#include <utils/fileutils.h>
+
+#include <QFile>
+#include <QJsonArray>
+#include <QJsonDocument>
+#include <QJsonObject>
+#include <QJsonValue>
+
+namespace MesonProjectManager {
+namespace Internal {
+
+class BuildSystemFilesParser
+{
+    std::vector<Utils::FilePath> m_files;
+    static void appendFiles(const std::optional<QJsonArray> &arr, std::vector<Utils::FilePath> &dest)
+    {
+        if (arr)
+            std::transform(std::cbegin(*arr),
+                           std::cend(*arr),
+                           std::back_inserter(dest),
+                           [](const auto &file) {
+                               return Utils::FilePath::fromString(file.toString());
+                           });
+    }
+
+public:
+    BuildSystemFilesParser(const QString &buildDir)
+    {
+        auto arr = load<QJsonArray>(QString("%1/%2/%3")
+                                        .arg(buildDir)
+                                        .arg(Constants::MESON_INFO_DIR)
+                                        .arg(Constants::MESON_INTRO_BUILDSYSTEM_FILES));
+        appendFiles(arr, m_files);
+    }
+
+    BuildSystemFilesParser(const QJsonDocument &js)
+    {
+        auto arr = get<QJsonArray>(js.object(), "projectinfo", "buildsystem_files");
+        appendFiles(arr, m_files);
+        const auto subprojects = get<QJsonArray>(js.object(), "projectinfo", "subprojects");
+        for (const auto &subproject : *subprojects) {
+            auto arr = get<QJsonArray>(subproject.toObject(), "buildsystem_files");
+            appendFiles(arr, m_files);
+        }
+    }
+
+    std::vector<Utils::FilePath> files() { return m_files; };
+};
+
+} // namespace Internal
+} // namespace MesonProjectManager