Fix less-than comparison for QStandardItem and QSortFilterProxyModel with invalid data.

Previously, QStandardItem::operator<() returned true when both
items had invalid data. With MSVC in debug mode (checked
iterators/STL), this triggered an assert in
tst_QStandardItem::sortChildren() since that verifies
that !(b < a) when a < b:

Debug Assertion Failed!
Line: 3006
Expression: invalid operator<

Introduce a stable sort order for invalid items such that
other items are always less than invalid items and comparing
invalid items returns false (indicating equivalence).

Change-Id: Ica0f0d9f001c86973b1941dbcc1faf282e4c47df
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/tests/auto/gui/itemmodels/qstandarditem/tst_qstandarditem.cpp b/tests/auto/gui/itemmodels/qstandarditem/tst_qstandarditem.cpp
index 5dce228ca0..2448b89296 100644
--- a/tests/auto/gui/itemmodels/qstandarditem/tst_qstandarditem.cpp
+++ b/tests/auto/gui/itemmodels/qstandarditem/tst_qstandarditem.cpp
@@ -81,6 +81,7 @@ private slots:
     void clone();
     void sortChildren();
     void subclassing();
+    void lessThan();
 };
 
 tst_QStandardItem::tst_QStandardItem()
@@ -1095,5 +1096,19 @@ void tst_QStandardItem::subclassing()
     QCOMPARE(item->child(2), (QStandardItem*)child1);
 }
 
+void tst_QStandardItem::lessThan()
+{
+    QStandardItem stringA("A");
+    QStandardItem stringB("B");
+    QStandardItem invalid1;
+    QStandardItem invalid2;
+    QVERIFY(stringA < stringB);
+    QVERIFY(!(stringB < stringA));
+    // Items with invalid data go to the end.
+    QVERIFY(stringA < invalid1);
+    QVERIFY(!(invalid1 < stringA));
+    QVERIFY(!(invalid1 < invalid2));
+}
+
 QTEST_MAIN(tst_QStandardItem)
 #include "tst_qstandarditem.moc"