QQmlComponentPrivate::setInitialProperty: improve error message

We can discern between the case where the property does not exist at
all, and the case where we cannot set it.

Change-Id: Ia2e8f4cc077a00b90d720db01bff1542a812dea0
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>
(cherry picked from commit 7275328b967582010abfd59c9a93feef4cb1379f)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

2 files changed, 8 insertions, 3 deletions

diff --git a/src/qml/qml/qqmlcomponent.cpp b/src/qml/qml/qqmlcomponent.cpp
index f35c3011d3..b44ad83b6e 100644
--- a/src/qml/qml/qqmlcomponent.cpp
+++ b/src/qml/qml/qqmlcomponent.cpp
@@ -375,10 +375,15 @@ bool QQmlComponentPrivate::setInitialProperty(QObject *component, const QString&
 {
     QQmlProperty prop = QQmlComponentPrivate::removePropertyFromRequired(component, name, requiredProperties());
     QQmlPropertyPrivate *privProp = QQmlPropertyPrivate::get(prop);
-    if (!prop.isValid() || !privProp->writeValueProperty(value, {})) {
+    const bool isValid = prop.isValid();
+    if (!isValid || !privProp->writeValueProperty(value, {})) {
         QQmlError error{};
         error.setUrl(url);
-        error.setDescription(QLatin1String("Could not set property %1").arg(name));
+        if (isValid)
+            error.setDescription(QLatin1String("Could not set initial property %1").arg(name));
+        else
+            error.setDescription(QLatin1String("Setting initial properties failed: %2 does not have a property called %1").arg(name,
+                                                                                            QQmlMetaType::prettyTypeName(component)));
         state.errors.push_back(error);
         return false;
     } else
diff --git a/tests/auto/qml/qqmlcomponent/tst_qqmlcomponent.cpp b/tests/auto/qml/qqmlcomponent/tst_qqmlcomponent.cpp
index c4a1a6aea4..c6c6a20724 100644
--- a/tests/auto/qml/qqmlcomponent/tst_qqmlcomponent.cpp
+++ b/tests/auto/qml/qqmlcomponent/tst_qqmlcomponent.cpp
@@ -829,7 +829,7 @@ void tst_qqmlcomponent::testSetInitialProperties()
             comp.createWithInitialProperties(QVariantMap { {"notThePropertiesYoureLookingFor", 42} })
         };
         QVERIFY(obj);
-        QVERIFY(comp.errorString().contains("Could not set property notThePropertiesYoureLookingFor"));
+        QVERIFY(comp.errorString().contains("Setting initial properties failed: Item does not have a property called notThePropertiesYoureLookingFor"));
     }
 }