QQmlTableInstanceModel: don't fall back to use DelegateChooser as delegate

If the application uses a DelegateChooser, but the chooser fails to
resolve a delegate for a certain index, it should not use itself
as the delegate instead. This will cause the application to crash.
Instead, we just print a warning, and return nullptr, which will let
TableView handle the situation gracefully.

Change-Id: Ibaf9da09fd11149362f5b674fc61db47593de10c
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

3 files changed, 82 insertions, 4 deletions

diff --git a/src/qml/types/qqmltableinstancemodel.cpp b/src/qml/types/qqmltableinstancemodel.cpp
index 33d13e3bad..1054158dc8 100644
--- a/src/qml/types/qqmltableinstancemodel.cpp
+++ b/src/qml/types/qqmltableinstancemodel.cpp
@@ -109,19 +109,19 @@ QQmlTableInstanceModel::~QQmlTableInstanceModel()
 
 QQmlComponent *QQmlTableInstanceModel::resolveDelegate(int index)
 {
-    QQmlComponent *delegate = nullptr;
     if (m_delegateChooser) {
         const int row = m_adaptorModel.rowAt(index);
         const int column = m_adaptorModel.columnAt(index);
+        QQmlComponent *delegate = nullptr;
         QQmlAbstractDelegateComponent *chooser = m_delegateChooser;
         do {
             delegate = chooser->delegate(&m_adaptorModel, row, column);
             chooser = qobject_cast<QQmlAbstractDelegateComponent *>(delegate);
         } while (chooser);
+        return delegate;
     }
-    if (!delegate)
-        delegate = m_delegate;
-    return delegate;
+
+    return m_delegate;
 }
 
 QQmlDelegateModelItem *QQmlTableInstanceModel::resolveModelItem(int index)
@@ -132,6 +132,8 @@ QQmlDelegateModelItem *QQmlTableInstanceModel::resolveModelItem(int index)
         return modelItem;
 
     QQmlComponent *delegate = resolveDelegate(index);
+    if (!delegate)
+        return nullptr;
 
     // Check if the pool contains an item that can be reused
     modelItem = takeFromReusableItemsPool(delegate);
diff --git a/tests/auto/quick/qquicktableview/data/usechooserwithoutdefault.qml b/tests/auto/quick/qquicktableview/data/usechooserwithoutdefault.qml
new file mode 100644
index 0000000000..847500d71f
--- /dev/null
+++ b/tests/auto/quick/qquicktableview/data/usechooserwithoutdefault.qml
@@ -0,0 +1,64 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQuick module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+import QtQuick 2.12
+import QtQuick.Window 2.3
+import Qt.labs.qmlmodels 1.0
+
+Item {
+    width: 640
+    height: 450
+
+    property alias tableView: tableView
+
+    TableView {
+        id: tableView
+        width: 600
+        height: 400
+        delegate: DelegateChooser {
+            DelegateChoice {
+                row: 0
+                delegate: Item {
+                    implicitWidth: 100
+                    implicitHeight: 100
+                }
+            }
+        }
+    }
+}
diff --git a/tests/auto/quick/qquicktableview/tst_qquicktableview.cpp b/tests/auto/quick/qquicktableview/tst_qquicktableview.cpp
index 4ba36cd687..45b3566574 100644
--- a/tests/auto/quick/qquicktableview/tst_qquicktableview.cpp
+++ b/tests/auto/quick/qquicktableview/tst_qquicktableview.cpp
@@ -135,6 +135,7 @@ private slots:
     void checkRowAndColumnChangedButNotIndex();
     void checkChangingModelFromDelegate();
     void checkRebuildViewportOnly();
+    void useDelegateChooserWithoutDefault();
 };
 
 tst_QQuickTableView::tst_QQuickTableView()
@@ -1756,6 +1757,17 @@ void tst_QQuickTableView::checkRebuildViewportOnly()
     QCOMPARE(countAfterRebuild, itemCountBeforeRebuild);
 }
 
+void tst_QQuickTableView::useDelegateChooserWithoutDefault()
+{
+    // Check that the application issues a warning (but doesn't e.g
+    // crash) if the delegate chooser doesn't cover all cells
+    QTest::ignoreMessage(QtWarningMsg, QRegularExpression(".*failed"));
+    LOAD_TABLEVIEW("usechooserwithoutdefault.qml");
+    auto model = TestModelAsVariant(2, 1);
+    tableView->setModel(model);
+    WAIT_UNTIL_POLISHED;
+};
+
 QTEST_MAIN(tst_QQuickTableView)
 
 #include "tst_qquicktableview.moc"