Inspector: Do not assert when trying to stream QModelIndex

Some QVariant's like QModelIndex cannot be streamed in a meaningful way:
QDataType::save() will return false for them. However, this leads to a
qWarning and Q_ASSERT in QVariant::operator<<().

To prevent this we're calling QDataType::save() manually beforehand. We
however throw away the result if it succeeds, and still call
QVariant::operator<<() to get the benefits of the QDataStream version
handling.

The alternatives would be to make QVariant::operator<<() not assert,
or blacklist all known types with problems manually. Both seem to
be difficult though ...

Change-Id: I4f5fe6d5a3a076c24fbc73371a4d12d720de53da
Task-number: QTBUG-42438
Reviewed-by: Ulf Hermann <ulf.hermann@theqtcompany.com>
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/src/qml/debugger/qqmlenginedebugservice.cpp b/src/qml/debugger/qqmlenginedebugservice.cpp
index cb533a0459..088f3203d6 100644
--- a/src/qml/debugger/qqmlenginedebugservice.cpp
+++ b/src/qml/debugger/qqmlenginedebugservice.cpp
@@ -96,8 +96,16 @@ QDataStream &operator>>(QDataStream &ds,
 QDataStream &operator<<(QDataStream &ds,
                         const QQmlEngineDebugService::QQmlObjectProperty &data)
 {
-    ds << (int)data.type << data.name << data.value << data.valueTypeName
-       << data.binding << data.hasNotifySignal;
+    ds << (int)data.type << data.name;
+    // check first whether the data can be saved
+    // (otherwise we assert in QVariant::operator<<)
+    QByteArray buffer;
+    QDataStream fakeStream(&buffer, QIODevice::WriteOnly);
+    if (QMetaType::save(fakeStream, data.value.type(), data.value.constData()))
+        ds << data.value;
+    else
+        ds << QVariant();
+    ds << data.valueTypeName << data.binding << data.hasNotifySignal;
     return ds;
 }