QSFPM: Support source model undergoing reset during setSourceModel

Since 9d8663c18e88cb0b5a65f86cfd7726f3d31e04d6, we print a warning when
endResetModel is called without beginResetModel.
This however triggers false positives with a QSFPM if we set a source
model which is resetting at this point in time:
The QSFPM reacts to the endResetModel signal in _q_sourceReset by
calling its own endResetModel, but it does not have the resetting flag
set.
Fix this by deferring the endResetModel work that we are doing in
setSourceModel if the source is undergoing reset.

Task-number: QTBUG-132775
Pick-to: 6.10 6.9 6.8 6.5
Change-Id: I363f2f34a06cc5de031fa87c6274322bf03bd77f
Reviewed-by: David Faure <david.faure@kdab.com>

src/corelib/itemmodels/qsortfilterproxymodel.cpp

@@ -2110,6 +2110,13 @@ void QSortFilterProxyModel::setSourceModel(QAbstractItemModel *sourceModel)
         QObjectPrivate::connect(d->model, &QAbstractItemModel::modelReset, d,
                                 &QSortFilterProxyModelPrivate::_q_sourceReset)
     };
+    /* check whether we are connecting to a model that is undergoing a reset currently.
+       If it is, _q_sourceReset will take care of calling endResetModel, and of
+       calling sort if necessary.
+    */
+    auto modelPrivate = d->model ? QAbstractItemModelPrivate::get(d->model) : nullptr;
+    if (modelPrivate && modelPrivate->resetting)
+        return;
     endResetModel();
     if (d->update_source_sort_column() && d->dynamic_sortfilter)
         d->sort();

tests/auto/corelib/itemmodels/qsortfilterproxymodel/tst_qsortfilterproxymodel.cpp

@@ -3663,6 +3663,18 @@ void tst_QSortFilterProxyModel::resetInvalidate()
     QCOMPARE(ok, works);
 }
 
+void tst_QSortFilterProxyModel::sourceModelInReset()
+{
+    QTest::failOnWarning();
+    QStandardItemModel m1;
+    QSortFilterProxyModel sfpm;
+    connect(&m1, &QAbstractItemModel::modelAboutToBeReset, &sfpm, [&]() {
+        sfpm.setSourceModel(&m1);
+    });
+    m1.clear();
+    QCOMPARE_EQ(sfpm.sourceModel(), &m1);
+}
+
 /**
  * A proxy which changes the background color for items ending in 'y' or 'r'
  */

tests/auto/corelib/itemmodels/qsortfilterproxymodel/tst_qsortfilterproxymodel.h

@@ -104,6 +104,7 @@ private slots:
     void unnecessaryMapCreation();
     void resetInvalidate_data();
     void resetInvalidate();
+    void sourceModelInReset();
 
     void testMultipleProxiesWithSelection();
     void mapSelectionFromSource();