QML and protobuf: Issue with repeated nested message

[Persson]

Hi,

I'm having some trouble using a repeated nested message as a property from C++ in QML, for example

syntax = "proto3";

package messages;

message Foo {
    string name = 1;
}

message Bar {
    string name = 1;
    Foo foo = 2;
    repeated Foo foos = 3;
    repeated string baz = 4;
}

being exposed as a property from C++ as

#ifndef BACKEND_H
#define BACKEND_H

#include <QObject>
#include <QQmlEngine>

#include "messages.qpb.h"

class Backend : public QObject
{
    Q_OBJECT
    QML_ELEMENT
    Q_PROPERTY(messages::Bar bar MEMBER bar_ WRITE setBar NOTIFY barChanged);
public:
    explicit Backend(QObject *parent = nullptr);
    void setBar(messages::Bar bar);
signals:
    void barChanged(messages::Bar);

private:
    messages::Bar bar_;
};

#endif // BACKEND_H

and in QML

import QtQuick
import QtQuick.Controls

Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")

    Label {
        text: {
            print(backend.bar)
            print(backend.bar.foo)
            print(backend.bar.foos)
            print(backend.bar.baz)
            return "Bar name: " + backend.bar.name
        }
    }
}

This results in "foos" being undefined in QML, the other fields work as expected. Seems like a bug? I created a minimal reproducing example here. I'm using Qt 6.10.2 on Debian 13. Any advice on how to proceed would be appreciated.

//Daniel

[Persson]

Indeed, this was a bug. More info here, in case anyone else comes across this: https://qt-project.atlassian.net/browse/QTBUG-145124