QmlCompiler: Explicitly cast operations that result in QString

We may be using QStringBuilder, and that can be stored in QVariant (and
possibly other places).

Fixes: QTBUG-125576
Change-Id: Ib31e31591a3333e51f1d5594ee05fdb8f0744714
Reviewed-by: Fabian Kosmale <[email protected]>

6 files changed, 95 insertions, 2 deletions

diff --git a/src/qmlcompiler/qqmljscodegenerator.cpp b/src/qmlcompiler/qqmljscodegenerator.cpp
index 9f609f39fb..1ef9194bdb 100644
--- a/src/qmlcompiler/qqmljscodegenerator.cpp
+++ b/src/qmlcompiler/qqmljscodegenerator.cpp
@@ -3639,9 +3639,13 @@ void QQmlJSCodeGenerator::generateArithmeticOperation(
     const QQmlJSRegisterContent originalOut = m_typeResolver->original(m_state.accumulatorOut());
     m_body += m_state.accumulatorVariableOut;
     m_body += u" = "_s;
+    const QString explicitCast
+            = m_typeResolver->equals(originalOut.storedType(), m_typeResolver->stringType())
+                ? originalOut.storedType()->internalName()
+                : QString();
     m_body += conversion(
                 originalOut, m_state.accumulatorOut(),
-                u'(' + lhs + u' ' + cppOperator + u' ' + rhs + u')');
+                explicitCast + u'(' + lhs + u' ' + cppOperator + u' ' + rhs + u')');
     m_body += u";\n"_s;
 }
 
diff --git a/tests/auto/qml/qmlcppcodegen/CMakeLists.txt b/tests/auto/qml/qmlcppcodegen/CMakeLists.txt
index 42ad6d23d6..715ad6162a 100644
--- a/tests/auto/qml/qmlcppcodegen/CMakeLists.txt
+++ b/tests/auto/qml/qmlcppcodegen/CMakeLists.txt
@@ -19,6 +19,8 @@ qt_internal_add_test(tst_qmlcppcodegen
         codegen_test_moduleplugin
         codegen_test_hidden
         codegen_test_hiddenplugin
+        codegen_test_stringbuilder
+        codegen_test_stringbuilderplugin
 )
 
 qt_internal_add_test(tst_qmlcppcodegen_interpreted
@@ -31,6 +33,8 @@ qt_internal_add_test(tst_qmlcppcodegen_interpreted
         codegen_test_moduleplugin
         codegen_test_hidden
         codegen_test_hiddenplugin
+        codegen_test_stringbuilder
+        codegen_test_stringbuilderplugin
     DEFINES
         QT_TEST_FORCE_INTERPRETER
 )
diff --git a/tests/auto/qml/qmlcppcodegen/data/CMakeLists.txt b/tests/auto/qml/qmlcppcodegen/data/CMakeLists.txt
index 8c5449d192..7f2e6ad967 100644
--- a/tests/auto/qml/qmlcppcodegen/data/CMakeLists.txt
+++ b/tests/auto/qml/qmlcppcodegen/data/CMakeLists.txt
@@ -346,6 +346,33 @@ add_dependencies(codegen_test_hidden Qt::Quick)
 
 qt_autogen_tools_initial_setup(codegen_test_hiddenplugin)
 
+qt_policy(SET QTP0004 NEW)
+
+qt_add_library(codegen_test_stringbuilder STATIC)
+qt_autogen_tools_initial_setup(codegen_test_stringbuilder)
+
+set_target_properties(codegen_test_stringbuilder PROPERTIES
+    # We really want qmlcachegen here, even if qmlsc is available
+    QT_QMLCACHEGEN_EXECUTABLE qmlcachegen
+    QT_QMLCACHEGEN_ARGUMENTS --validate-basic-blocks
+)
+
+target_compile_definitions(codegen_test_stringbuilder PRIVATE
+    -DGENERATED_CPP_FOLDER="${CMAKE_CURRENT_BINARY_DIR}/.rcc/qmlcache"
+    QT_USE_QSTRINGBUILDER
+)
+
+qt6_add_qml_module(codegen_test_stringbuilder
+    URI StringBuilderTestTypes
+    SOURCES
+        writableVariantMap.h
+    QML_FILES
+        writeVariantMap.qml
+    OUTPUT_DIRECTORY stringbuilderTestTypes
+    __QT_INTERNAL_DISAMBIGUATE_QMLDIR_RESOURCE
+)
+
+qt_autogen_tools_initial_setup(codegen_test_stringbuilderplugin)
 
 qt_add_library(codegen_test_module STATIC)
 qt_autogen_tools_initial_setup(codegen_test_module)
@@ -356,7 +383,7 @@ set_target_properties(codegen_test_module PROPERTIES
     QT_QMLCACHEGEN_ARGUMENTS --validate-basic-blocks
 )
 
-qt_policy(SET QTP0004 NEW)
+
 
 target_compile_definitions(codegen_test_module PUBLIC
     -DGENERATED_CPP_FOLDER="${CMAKE_CURRENT_BINARY_DIR}/.rcc/qmlcache"
diff --git a/tests/auto/qml/qmlcppcodegen/data/writableVariantMap.h b/tests/auto/qml/qmlcppcodegen/data/writableVariantMap.h
new file mode 100644
index 0000000000..3c0fedd28b
--- /dev/null
+++ b/tests/auto/qml/qmlcppcodegen/data/writableVariantMap.h
@@ -0,0 +1,31 @@
+#pragma once
+#include <QObject>
+#include <QVariantMap>
+#include <QtQml/qqmlregistration.h>
+
+class WritableVariantMap : public QObject
+{
+    Q_OBJECT
+    QML_ELEMENT
+    Q_PROPERTY(QVariantMap data READ data WRITE setData NOTIFY dataChanged)
+
+public:
+    WritableVariantMap(QObject *parent = nullptr) : QObject(parent) { }
+
+    QVariantMap data() const { return m_data; }
+    void setData(const QVariantMap &data)
+    {
+        if (m_data != data) {
+            m_data = data;
+            emit dataChanged();
+        }
+    }
+
+signals:
+    void dataChanged();
+
+private:
+    QVariantMap m_data;
+};
+
+
diff --git a/tests/auto/qml/qmlcppcodegen/data/writeVariantMap.qml b/tests/auto/qml/qmlcppcodegen/data/writeVariantMap.qml
new file mode 100644
index 0000000000..536e53b408
--- /dev/null
+++ b/tests/auto/qml/qmlcppcodegen/data/writeVariantMap.qml
@@ -0,0 +1,10 @@
+pragma Strict
+import StringBuilderTestTypes
+
+WritableVariantMap {
+    id: dragSource
+    property string modelData: "Drag Me"
+    data: ({
+        "text/plain": "%" + dragSource.modelData + "%"
+    })
+}
diff --git a/tests/auto/qml/qmlcppcodegen/tst_qmlcppcodegen.cpp b/tests/auto/qml/qmlcppcodegen/tst_qmlcppcodegen.cpp
index 9b66143f62..53cc068e8c 100644
--- a/tests/auto/qml/qmlcppcodegen/tst_qmlcppcodegen.cpp
+++ b/tests/auto/qml/qmlcppcodegen/tst_qmlcppcodegen.cpp
@@ -256,6 +256,7 @@ private slots:
     void voidConversion();
     void voidFunction();
     void writeBack();
+    void writeVariantMap();
 };
 
 static QByteArray arg1()
@@ -5107,6 +5108,22 @@ void tst_QmlCppCodegen::writeBack()
     QCOMPARE(person->property("ints"), QVariant::fromValue(QList<int>({12, 22, 2, 1, 0, 0, 33})));
 }
 
+void tst_QmlCppCodegen::writeVariantMap()
+{
+    QQmlEngine engine;
+    QQmlComponent component(&engine, QUrl(u"qrc:/qt/qml/StringBuilderTestTypes/writeVariantMap.qml"_s));
+    QVERIFY2(component.isReady(), qPrintable(component.errorString()));
+    QScopedPointer<QObject> object(component.create());
+    QVERIFY(!object.isNull());
+
+    const QVariantMap v = object->property("data").toMap();
+    QCOMPARE(v.size(), 1);
+    const QVariant textPlain = v[u"text/plain"_s];
+    QCOMPARE(textPlain.metaType(), QMetaType::fromType<QString>());
+    QCOMPARE(textPlain.toString(), u"%Drag Me%"_s);
+
+}
+
 QTEST_MAIN(tst_QmlCppCodegen)
 
 #include "tst_qmlcppcodegen.moc"