Clarify docs that everything must be re-queried on model reset.

Change-Id: I05970302d4f52d092a7c65a45b9e5a3570b1d144
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>

2 files changed, 42 insertions, 4 deletions

diff --git a/src/corelib/itemmodels/qabstractitemmodel.cpp b/src/corelib/itemmodels/qabstractitemmodel.cpp
index dec1fe4cef..a2776271a8 100644
--- a/src/corelib/itemmodels/qabstractitemmodel.cpp
+++ b/src/corelib/itemmodels/qabstractitemmodel.cpp
@@ -2141,9 +2141,7 @@ QSize QAbstractItemModel::span(const QModelIndex &) const
     Sets the model's role names to \a roleNames.
 
     This function allows mapping of role identifiers to role property names in
-    Declarative UI.  This function must be called before the model is used.
-    Modifying the role names after the model has been set may result in
-    undefined behaviour.
+    scripting languages.
 
     \sa roleNames()
 */
@@ -3420,6 +3418,11 @@ bool QAbstractListModel::dropMimeData(const QMimeData *data, Qt::DropAction acti
     This signal is emitted when reset() is called, after the model's internal
     state (e.g. persistent model indexes) has been invalidated.
 
+    Note that if a model is reset it should be considered that all information
+    previously retrieved from it is invalid. This includes but is not limited
+    to the rowCount() and columnCount(), flags(), data retrieved through data(),
+    and roleNames().
+
     \sa endResetModel(), modelAboutToBeReset()
 */
 
diff --git a/tests/auto/corelib/itemmodels/qabstractitemmodel/tst_qabstractitemmodel.cpp b/tests/auto/corelib/itemmodels/qabstractitemmodel/tst_qabstractitemmodel.cpp
index af1e492a8b..8829f6e7b1 100644
--- a/tests/auto/corelib/itemmodels/qabstractitemmodel/tst_qabstractitemmodel.cpp
+++ b/tests/auto/corelib/itemmodels/qabstractitemmodel/tst_qabstractitemmodel.cpp
@@ -1669,6 +1669,19 @@ private:
 };
 
 
+class ModelWithCustomRole : public QStringListModel
+{
+  Q_OBJECT
+public:
+  ModelWithCustomRole(QObject *parent = 0)
+    : QStringListModel(parent)
+  {
+    QHash<int, QByteArray> roleNames_ = roleNames();
+    roleNames_.insert(Qt::UserRole + 1, "custom");
+    setRoleNames(roleNames_);
+  }
+};
+
 ListenerObject::ListenerObject(QAbstractProxyModel *parent)
     : QObject(parent), m_model(parent)
 {
@@ -1722,7 +1735,7 @@ void tst_QAbstractItemModel::testReset()
     nullProxy->setSourceModel(m_model);
 
     // Makes sure the model and proxy are in a consistent state. before and after reset.
-    new ListenerObject(nullProxy);
+    ListenerObject *listener = new ListenerObject(nullProxy);
 
     ModelResetCommandFixed *resetCommand = new ModelResetCommandFixed(m_model, this);
 
@@ -1741,6 +1754,28 @@ void tst_QAbstractItemModel::testReset()
     QVERIFY(m_model->rowCount() == 9);
     QModelIndex destIndex = m_model->index(4, 0);
     QVERIFY(m_model->rowCount(destIndex) == 11);
+
+    // Delete it because its slots test things which are not true after this point.
+    delete listener;
+
+    QSignalSpy proxyBeforeResetSpy(nullProxy, SIGNAL(modelAboutToBeReset()));
+    QSignalSpy proxyAfterResetSpy(nullProxy, SIGNAL(modelReset()));
+
+    // Before setting it, it does not have custom roles.
+    QCOMPARE(nullProxy->roleNames().value(Qt::UserRole + 1), QByteArray());
+
+    nullProxy->setSourceModel(new ModelWithCustomRole(this));
+    QVERIFY(proxyBeforeResetSpy.size() == 1);
+    QVERIFY(proxyAfterResetSpy.size() == 1);
+
+    QCOMPARE(nullProxy->roleNames().value(Qt::UserRole + 1), QByteArray("custom"));
+
+    nullProxy->setSourceModel(m_model);
+    QVERIFY(proxyBeforeResetSpy.size() == 2);
+    QVERIFY(proxyAfterResetSpy.size() == 2);
+
+    // After being reset the proxy must be queried again.
+    QCOMPARE(nullProxy->roleNames().value(Qt::UserRole + 1), QByteArray());
 }
 
 class CustomRoleModel : public QStringListModel