QML Binding: do not convert strings

The root cause for the issue is that QQmlObjectCreator::setPropertyValue
calls QQmlStringConverters::variantFromString on strings if the property
is of type QVariant. Unfortunately, this cannot be changed easily as the
current behavior is explicitly documented and tested in tst_qqmllanguage,
thus making it a breaking change.

As a workaround, QML Binding does now take a QJSValue instead of a
QVariant (making value a var property), which does not trigger the
conversion path.

Fixes: QTBUG-78943
Change-Id: I0b64dffdb6b84b2bab2bb85a8cb263e530c18570
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 30 insertions, 0 deletions

diff --git a/tests/auto/qml/qqmlbinding/data/noUnexpectedStringConversion.qml b/tests/auto/qml/qqmlbinding/data/noUnexpectedStringConversion.qml
new file mode 100644
index 0000000000..d0f30c5da5
--- /dev/null
+++ b/tests/auto/qml/qqmlbinding/data/noUnexpectedStringConversion.qml
@@ -0,0 +1,30 @@
+import QtQuick 2.12
+import QtQuick.Window 2.12
+
+Window {
+visible: true
+width: 640
+height: 480
+title: qsTr("Hello World")
+
+    Rectangle {
+        id: colorRect
+        objectName: "colorRect"
+        anchors.fill: parent
+        Text {
+            objectName: "colorLabel"
+            id: colorLabel
+        }
+    }
+
+    Binding {
+        target: colorLabel
+        property: "text"
+        value: "red"
+    }
+    Binding {
+        target: colorRect
+        property: "color"
+        value: "red"
+    }
+}