QML: Warn about relative QRC path

A runtime warning will now be issued if a relative QRC path is passed:
a relative QRC path doesn't make a lot of sense, but it works
to some extent (therefore it's only a warning).

Task-number: QTCREATORBUG-32198
Change-Id: Ifd55013d01589149128ce5d3b31fd6748186fd05
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

src/qml/qml/qqmlapplicationengine.cpp

@@ -11,6 +11,8 @@
 #include <QtQml/private/qqmldirdata_p.h>
 #include <QtQml/private/qqmlfileselector_p.h>
 
+using namespace Qt::Literals::StringLiterals;
+
 QT_BEGIN_NAMESPACE
 
 QQmlApplicationEnginePrivate::QQmlApplicationEnginePrivate(QQmlEngine *e)
@@ -85,18 +87,19 @@ void QQmlApplicationEnginePrivate::_q_loadTranslations()
 #endif
 }
 
+static QString translationsDirectoryFromLocalUrl(const QUrl &url)
+{
+    QFileInfo fi(QQmlFile::urlToLocalFileOrQrc(url));
+    return fi.path() + "/i18n"_L1;
+}
+
 void QQmlApplicationEnginePrivate::startLoad(const QUrl &url, const QByteArray &data, bool dataFlag)
 {
     Q_Q(QQmlApplicationEngine);
 
     ensureInitialized();
 
-    if (url.scheme() == QLatin1String("file") || url.scheme() == QLatin1String("qrc")) {
-        QFileInfo fi(QQmlFile::urlToLocalFileOrQrc(url));
-        translationsDirectory = fi.path() + QLatin1String("/i18n");
-    } else {
-        translationsDirectory.clear();
-    }
+    updateTranslationDirectory(url);
 
     _q_loadTranslations(); //Translations must be loaded before the QML file is
     QQmlComponent *c = new QQmlComponent(q, q);
@@ -125,12 +128,9 @@ void QQmlApplicationEnginePrivate::startLoad(QAnyStringView uri, QAnyStringView
     if (type.sourceUrl().isValid()) {
         const auto qmlDirData = typeLoader.getQmldir(type.sourceUrl());
         const QUrl url = qmlDirData->finalUrl();
-        if (url.scheme() == QLatin1String("file") || url.scheme() == QLatin1String("qrc")) {
-            QFileInfo fi(QQmlFile::urlToLocalFileOrQrc(url));
-            translationsDirectory = fi.path() + QLatin1String("/i18n");
-        } else {
-            translationsDirectory.clear();
-        }
+        // A QRC URL coming from a qmldir cannot contain a relative path
+        Q_ASSERT(url.scheme() != "qrc"_L1 || url.path().startsWith('/'_L1));
+        updateTranslationDirectory(url);
     }
 
     /* Translations must be loaded before the QML file. They require translationDirectory to
@@ -188,6 +188,18 @@ void QQmlApplicationEnginePrivate::ensureLoadingFinishes(QQmlComponent *c)
     QObject::connect(c, &QQmlComponent::statusChanged, q, [this, c] { this->finishLoad(c); });
 }
 
+void QQmlApplicationEnginePrivate::updateTranslationDirectory(const QUrl &url)
+{
+    const QString scheme = url.scheme();
+    if (scheme == "file"_L1) {
+        translationsDirectory = translationsDirectoryFromLocalUrl(url);
+    } else if (scheme == "qrc"_L1) {
+        translationsDirectory = translationsDirectoryFromLocalUrl(url);
+    } else {
+        translationsDirectory.clear();
+    }
+}
+
 /*!
   \class QQmlApplicationEngine
   \since 5.1

src/qml/qml/qqmlapplicationengine_p.h

@@ -39,6 +39,8 @@ public:
     void _q_loadTranslations();
     void finishLoad(QQmlComponent *component);
     void ensureLoadingFinishes(QQmlComponent *component);
+    void updateTranslationDirectory(const QUrl &url);
+
     QList<QObject *> objects;
     QVariantMap initialProperties;
     QStringList extraFileSelectors;

src/qml/qml/qqmlcomponent.cpp

@@ -797,6 +797,12 @@ void QQmlComponentPrivate::loadUrl(const QUrl &newUrl, QQmlComponent::Compilatio
         m_url = newUrl;
     }
 
+    if (m_url.scheme() == "qrc"_L1 && !m_url.path().startsWith("/"_L1)) {
+        qWarning().nospace().noquote()
+                << "QQmlComponent: attempted to load via a relative URL '" << m_url.toString()
+                << "' in resource file system. This is not fully supported and may not work";
+    }
+
     if (newUrl.isEmpty()) {
         QQmlError error;
         error.setDescription(QQmlComponent::tr("Invalid empty URL"));

tests/auto/qml/qqmlapplicationengine/tst_qqmlapplicationengine.cpp

@@ -11,6 +11,8 @@
 #include <QDebug>
 #include <QtQuickTestUtils/private/qmlutils_p.h>
 
+using namespace Qt::Literals::StringLiterals;
+
 class tst_qqmlapplicationengine : public QQmlDataTest
 {
     Q_OBJECT
@@ -33,6 +35,7 @@ private slots:
     void translationChange();
     void setInitialProperties();
     void failureToLoadTriggersWarningSignal();
+    void relativeQrcPathTriggersWarningSignal();
     void errorWhileCreating();
     void createWithQrcPath();
 
@@ -370,6 +373,24 @@ void tst_qqmlapplicationengine::failureToLoadTriggersWarningSignal()
     QTRY_COMPARE(warningObserver.size(), 1);
 }
 
+void tst_qqmlapplicationengine::relativeQrcPathTriggersWarningSignal()
+{
+    const auto url = QUrl("qrc:main.qml");
+    qRegisterMetaType<QList<QQmlError>>();
+    QTest::ignoreMessage(QtMsgType::QtWarningMsg, "QQmlApplicationEngine failed to load component");
+    QTest::ignoreMessage(
+            QtMsgType::QtWarningMsg,
+            "QQmlComponent: attempted to load via a relative URL '%1' in resource file system. "
+            "This is not fully supported and may not work"_L1.arg(url.toString())
+                    .toLocal8Bit()
+                    .data());
+    QTest::ignoreMessage(QtMsgType::QtWarningMsg, "qrc:main.qml: No such file or directory");
+    QQmlApplicationEngine test;
+    const QSignalSpy warningObserver(&test, &QQmlApplicationEngine::warnings);
+    test.load(url);
+    QTRY_COMPARE(warningObserver.size(), 1);
+}
+
 void tst_qqmlapplicationengine::errorWhileCreating()
 {
     auto url = testFileUrl("requiredViolation.qml");

tests/auto/qml/qqmlcomponent/tst_qqmlcomponent.cpp

@@ -151,6 +151,7 @@ private slots:
     void loadFromModuleRequired();
     void loadUrlRequired();
     void loadFromQrc();
+    void loadFromRelativeQrcPath();
     void removeBinding();
     void complexObjectArgument();
     void bindingEvaluationOrder();
@@ -1636,6 +1637,20 @@ void tst_qqmlcomponent::loadFromQrc()
     QVERIFY(p->compilationUnit()->baseCompilationUnit()->aotCompiledFunctions);
 }
 
+void tst_qqmlcomponent::loadFromRelativeQrcPath()
+{
+    QQmlEngine e;
+    QQmlComponent c(&e);
+    const QUrl url = QUrl("qrc:main.qml");
+    QTest::ignoreMessage(
+            QtMsgType::QtWarningMsg,
+            "QQmlComponent: attempted to load via a relative URL '%1' in resource file system. "
+            "This is not fully supported and may not work"_L1.arg(url.toString())
+                    .toLocal8Bit()
+                    .data());
+    c.loadUrl(url);
+}
+
 void tst_qqmlcomponent::removeBinding()
 {
     QQmlEngine e;

tests/auto/quick/qquickview/tst_qquickview.cpp

@@ -33,6 +33,7 @@ private slots:
     void fromModuleCtor();
     void loadFromModule_data();
     void loadFromModule();
+    void setSourceRelativeQrcPath();
     void overlay();
 };
 
@@ -343,6 +344,20 @@ void tst_QQuickView::loadFromModule()
     QCOMPARE(view.source(), url);
 }
 
+void tst_QQuickView::setSourceRelativeQrcPath()
+{
+    QQuickView view;
+    const auto url = QUrl("qrc:main.qml");
+    QTest::ignoreMessage(
+            QtMsgType::QtWarningMsg,
+            "QQmlComponent: attempted to load via a relative URL '%1' in resource file system. "
+            "This is not fully supported and may not work"_L1.arg(url.toString())
+                    .toLocal8Bit()
+                    .data());
+    QTest::ignoreMessage(QtMsgType::QtWarningMsg, "qrc:main.qml: No such file or directory");
+    view.setSource(url);
+}
+
 void tst_QQuickView::overlay()
 {
     QTest::ignoreMessage(QtWarningMsg,