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** This file is part of the test suite of the Qt Toolkit.
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#include "../../shared/util.h"
#include <QtCore/QObject>
#include <QtQml/qqml.h>
#include <QtQml/QQmlEngine>
#include <QtQml/QQmlComponent>
#include <private/qhashedstring_p.h>
#include <private/qqmlmetatype_p.h>

//Separate test, because if engine cleanup attempts fail they can easily break unrelated tests
class tst_qqmlenginecleanup : public QQmlDataTest
{
    Q_OBJECT
public:
    tst_qqmlenginecleanup() {}

private slots:
    void test_qmlClearTypeRegistrations();
    void test_valueTypeProviderModule(); // QTBUG-43004
};

// A wrapper around QQmlComponent to ensure the temporary reference counts
// on the type data as a result of the main thread <> loader thread communication
// are dropped. Regular Synchronous loading will leave us with an event posted
// to the gui thread and an extra refcount that will only be dropped after the
// event delivery. A plain sendPostedEvents() however is insufficient because
// we can't be sure that the event is posted after the constructor finished.
class CleanlyLoadingComponent : public QQmlComponent
{
public:
    CleanlyLoadingComponent(QQmlEngine *engine, const QUrl &url)
        : QQmlComponent(engine, url, QQmlComponent::Asynchronous)
    { waitForLoad(); }
    CleanlyLoadingComponent(QQmlEngine *engine, const QString &fileName)
        : QQmlComponent(engine, fileName, QQmlComponent::Asynchronous)
    { waitForLoad(); }

    void waitForLoad()
    {
        QTRY_VERIFY(status() == QQmlComponent::Ready || status() == QQmlComponent::Error);
    }
};

void tst_qqmlenginecleanup::test_qmlClearTypeRegistrations()
{
    //Test for preventing memory leaks is in tests/manual/qmltypememory
    QQmlEngine* engine;
    CleanlyLoadingComponent* component;
    QUrl testFile = testFileUrl("types.qml");

    const auto qmlTypeForTestType = []() {
        return QQmlMetaType::qmlType(QStringLiteral("TestTypeCpp"), QStringLiteral("Test"), 2, 0);
    };

    QVERIFY(!qmlTypeForTestType().isValid());
    qmlRegisterType<QObject>("Test", 2, 0, "TestTypeCpp");
    QVERIFY(qmlTypeForTestType().isValid());

    engine = new QQmlEngine;
    component = new CleanlyLoadingComponent(engine, testFile);
    QVERIFY(component->isReady());

    delete component;
    delete engine;

    {
        auto cppType = qmlTypeForTestType();

        qmlClearTypeRegistrations();
        QVERIFY(!qmlTypeForTestType().isValid());

        // cppType should hold the last ref, qmlClearTypeRegistration should have wiped
        // all internal references.
        QCOMPARE(QQmlType::refCount(cppType.priv()), 1);
    }

    //2nd run verifies that types can reload after a qmlClearTypeRegistrations
    qmlRegisterType<QObject>("Test", 2, 0, "TestTypeCpp");
    QVERIFY(qmlTypeForTestType().isValid());
    engine = new QQmlEngine;
    component = new CleanlyLoadingComponent(engine, testFile);
    QVERIFY(component->isReady());

    delete component;
    delete engine;
    qmlClearTypeRegistrations();
    QVERIFY(!qmlTypeForTestType().isValid());

    //3nd run verifies that TestTypeCpp is no longer registered
    engine = new QQmlEngine;
    component = new CleanlyLoadingComponent(engine, testFile);
    QVERIFY(component->isError());
    QCOMPARE(component->errorString(),
            testFile.toString() +":33 module \"Test\" is not installed\n");

    delete component;
    delete engine;
}

static void cleanState(QQmlEngine **e)
{
    delete *e;
    qmlClearTypeRegistrations();
    *e = new QQmlEngine;
    QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete);
    QCoreApplication::processEvents();
}

void tst_qqmlenginecleanup::test_valueTypeProviderModule()
{
    // this test ensures that a module which installs a value type
    // provider can be reinitialized after multiple calls to
    // qmlClearTypeRegistrations() without causing cycles in the
    // value type provider list.
    QQmlEngine *e = 0;
    QUrl testFile1 = testFileUrl("testFile1.qml");
    QUrl testFile2 = testFileUrl("testFile2.qml");
    bool noCycles = false;
    for (int i = 0; i < 20; ++i) {
        cleanState(&e);
        QQmlComponent c(e, this);
        c.loadUrl(i % 2 == 0 ? testFile1 : testFile2); // this will hang if cycles exist.
    }
    delete e;
    e = 0;
    noCycles = true;
    QVERIFY(noCycles);

    // this test ensures that no crashes occur due to using
    // a dangling QQmlType pointer in the type compiler
    // which results from qmlClearTypeRegistrations()
    QUrl testFile3 = testFileUrl("testFile3.qml");
    bool noDangling = false;
    for (int i = 0; i < 20; ++i) {
        cleanState(&e);
        QQmlComponent c(e, this);
        c.loadUrl(i % 2 == 0 ? testFile1 : testFile3); // this will crash if dangling ptr exists.
    }
    delete e;
    noDangling = true;
    QVERIFY(noDangling);
}

QTEST_MAIN(tst_qqmlenginecleanup)

#include "tst_qqmlenginecleanup.moc"