Restrict comparison of variants

Comparing two variants will not try to convert the types
of the variant anymore. Exceptions are when both types are
numeric types or one type is numeric and the other one a
QString. The exceptions are there to keep compatibility with
C++ and to not completely break QSettings (which needs automatic
conversions from QString to numeric types).

[ChangeLog][Important Behavior Changes] Comparing two
variants in Qt 6 will not try attempt any type conversions before
comparing the variants anymore. Instead variants of different type
will not compare equal, with two exceptions: If both types are numeric
types they will get compared according to C++ type promotion rules. If
one type is a QString and the other type a numeric type, a conversion
from the string to the numeric tpye will be attempted.

Fixes: QTBUG-84636
Change-Id: I0cdd0b7259a525a41679fb6761f1e37e1d5b257f
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/tests/auto/corelib/serialization/json/tst_qtjson.cpp b/tests/auto/corelib/serialization/json/tst_qtjson.cpp
index 82ad404932..b11d8c996d 100644
--- a/tests/auto/corelib/serialization/json/tst_qtjson.cpp
+++ b/tests/auto/corelib/serialization/json/tst_qtjson.cpp
@@ -1361,7 +1361,7 @@ void tst_QtJson::fromVariant_data()
     jsonObject["null"] = QJsonValue::Null;
     jsonObject["default"] = QJsonValue();
 
-    QTest::newRow("default") << QVariant() <<  QJsonValue(QJsonValue::Null);
+    QTest::newRow("default") << QVariant() <<  QJsonValue();
     QTest::newRow("nullptr") << QVariant::fromValue(nullptr) <<  QJsonValue(QJsonValue::Null);
     QTest::newRow("bool") << QVariant(boolValue) <<  QJsonValue(boolValue);
     QTest::newRow("int") << QVariant(intValue) <<  QJsonValue(intValue);
@@ -1391,6 +1391,14 @@ static QVariant normalizedVariant(const QVariant &v)
             out << normalizedVariant(v);
         return out;
     }
+    case QMetaType::QStringList: {
+        const QStringList in = v.toStringList();
+        QVariantList out;
+        out.reserve(in.size());
+        for (const QString &v : in)
+            out << v;
+        return out;
+    }
     case QMetaType::QVariantMap: {
         const QVariantMap in = v.toMap();
         QVariantMap out;
@@ -1400,7 +1408,7 @@ static QVariant normalizedVariant(const QVariant &v)
     }
     case QMetaType::QVariantHash: {
         const QVariantHash in = v.toHash();
-        QVariantHash out;
+        QVariantMap out;
         for (auto it = in.begin(); it != in.end(); ++it)
             out.insert(it.key(), normalizedVariant(it.value()));
         return out;