QJSValue: convert more aggressively to QVariant

Normally, we don't want to convert aggressively between JS objects and
QVariant, as that is prone to losing information. However,
QJSValue::toVariant is documented to attempt lossy conversions. Restore
the behavior of Qt < 6.5.3 for it. This is done by replacing the boolean
indicating we should wrap JS objects into QJSValue with an enum instead.
That enum introduces a third state ("Aggressive"), which is only used
for QJSValue::toVariant. All other users of QJSEngine::toVariant behave
as before (post 6.5.3).
Function objects are still not converted, as we know that this would be
a futile attempt, and more importantly, to keep the behavior that
existed  before Qt 6.5.3.
Amends 43077556550c6b17226a7d393ec844b605c9c678 which introduced the
regression and afe96c4d633146df477012975824b8ab65034239 which  fixed the
issue only partially.

Pick-to: 6.5 6.6 6.7
Fixes: QTBUG-119963
Change-Id: I07d9901437812579ac5b873a4dff4de60c8f617e
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/tests/auto/qml/qjsvalue/tst_qjsvalue.cpp b/tests/auto/qml/qjsvalue/tst_qjsvalue.cpp
index ada191d863..6c7612b77e 100644
--- a/tests/auto/qml/qjsvalue/tst_qjsvalue.cpp
+++ b/tests/auto/qml/qjsvalue/tst_qjsvalue.cpp
@@ -1113,6 +1113,25 @@ void tst_QJSValue::toVariant()
 
         QCOMPARE(func.toVariant().metaType(), QMetaType::fromType<QJSValue>());
     }
+
+    // object with custom prototype
+    {
+        QJSValue object = eng.evaluate(R"js(
+        (function(){
+            function Person(firstName, lastName) {
+                    this.firstName = firstName;
+                    this.lastName = lastName;
+            }
+            return new Person("John", "Doe");
+        })();
+        )js");
+        QVERIFY(object.isObject());
+        auto asVariant = object.toVariant();
+        QCOMPARE(asVariant.metaType(), QMetaType::fromType<QVariantMap>());
+        auto variantMap = asVariant.value<QVariantMap>();
+        QVERIFY(variantMap.contains("firstName"));
+        QCOMPARE(variantMap["firstName"].toString(), "John");
+    }
 }
 
 void tst_QJSValue::toPrimitive_data()