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  1. Qt
  2. QTBUG-41403

QVariant associative container conversion misses built-in check.

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    Description

      It is possible to convert from a QMap<QString, T> to a QVariantMap or a QVariantHash via QVariant::value(), where T is a user-chosen type which is a metatype. The conversion uses a custom converter.

      If T is QVariant, the type is a QVariantMap, which is a built-in metatype. That means there is no user-specified converter.

      That means that if a QVariant contains a QMap<QString, int>, then var.value<QVariantHash>() works, but if it contains a QVariantMap, then var.value<QVariantHash>() does not work.

      QVariantValueHelperInterface<QVariantHash> and QVariantValueHelperInterface<QVariantMap> only check for user-defined converters, but should also check if the contained type is exactly a built-in metatype.

      QVariantValueHelperInterface<QVariantList> already has such a check for built-ins, so it does not exhibit a comparable bug.

        QMap<QString, int> mp;
  QVariantMap varmp;
  mp.insert("3", 4);
  varmp.insert("3", 4);

  QStringList li;
  li.append("Hello");
  QVariantList varli;
  varli.append("World");

  QVariant var;

  var = QVariant::fromValue(li);
  qDebug() << var.value<QVariantList>();

  var = QVariant::fromValue(varli);
  qDebug() << var.value<QVariantList>();

  var = QVariant::fromValue(mp);
  qDebug() << var.value<QVariantHash>();

  var = QVariant::fromValue(varmp);
  qDebug() << var.value<QVariantHash>();

  qDebug() << QMetaType::hasRegisteredConverterFunction(qMetaTypeId<QVariantList>(), qMetaTypeId<QtMetaTypePrivate::QSequentialIterableImpl>());
  qDebug() << QMetaType::hasRegisteredConverterFunction(qMetaTypeId<QStringList>(), qMetaTypeId<QtMetaTypePrivate::QSequentialIterableImpl>());
  qDebug() << QMetaType::hasRegisteredConverterFunction(qMetaTypeId<QVariantHash>(), qMetaTypeId<QtMetaTypePrivate::QAssociativeIterableImpl>());
  qDebug() << QMetaType::hasRegisteredConverterFunction(qMetaTypeId<QVariantMap>(), qMetaTypeId<QtMetaTypePrivate::QAssociativeIterableImpl>());
  qDebug() << QMetaType::hasRegisteredConverterFunction(qMetaTypeId<QMap<int, int> >(), qMetaTypeId<QtMetaTypePrivate::QAssociativeIterableImpl>());
  qDebug() << QMetaType::hasRegisteredConverterFunction(qMetaTypeId<QHash<QString, int> >(), qMetaTypeId<QtMetaTypePrivate::QAssociativeIterableImpl>());

      Output

      (QVariant(QString, "Hello") ) 
(QVariant(QString, "World") ) 
QHash(("3", QVariant(int, 4) ) ) 
QHash()
false
false
false
false
true
true

      Attachments

        For Gerrit Dashboard: QTBUG-41403
        # Subject Branch Project Status CR V
        97743,6 Fix QVariant associative container conversion from built-in types. 5.4 qt/qtbase Status: MERGED +2 0
        123169,2 Avoid recreating QVariantLists when extracted from a QVariant 5.6 qt/qtbase Status: MERGED +2 0

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          People

            nierob Nierob
            steveire Stephen Kelly (Personal)
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            Dates

              Created:
              Updated:
              Resolved:

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