QFlatMap: add insert_or_assign

This does exactly what insert() on Qt associative containers does, but
allows to express the intent of using the STL-incompatible Qt insert()
semantics, in an STL-compatible way, instead of leaving the reader of
the code wondering what semantics are expected.

This is part of a very-long-term goal of fixing Qt associative
container's insert() behavior, in which QFlatMap, being an affected,
but private-API type, is used for proof-of-concept purposes.

Task-number: QTBUG-99651
Pick-to: 6.3 6.2
Change-Id: I69010285438259918aef659d3235180c1b5be696
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

src/corelib/tools/qflatmap_p.h

@@ -750,6 +750,24 @@ public:
         }
     }
 
+    template <typename M>
+    std::pair<iterator, bool> insert_or_assign(const Key &key, M &&obj)
+    {
+        auto r = try_emplace(key, std::forward<M>(obj));
+        if (!r.second)
+            *toValuesIterator(r.first) = std::forward<M>(obj);
+        return r;
+    }
+
+    template <typename M>
+    std::pair<iterator, bool> insert_or_assign(Key &&key, M &&obj)
+    {
+        auto r = try_emplace(std::move(key), std::forward<M>(obj));
+        if (!r.second)
+            *toValuesIterator(r.first) = std::forward<M>(obj);
+        return r;
+    }
+
     template <class InputIt, is_compatible_iterator<InputIt> = nullptr>
     void insert(InputIt first, InputIt last)
     {

src/plugins/platforms/cocoa/qnsview_tablet.mm

@@ -224,7 +224,7 @@ static const QPointingDevice *tabletToolInstance(NSEvent *theEvent)
     QWindowSystemInterface::handleTabletEnterLeaveProximityEvent(nullptr, timestamp, device, theEvent.isEnteringProximity);
     // The windowSystemId starts at 0, but is "unique" while in proximity
     if (theEvent.isEnteringProximity)
-        devicesInProximity->insert(windowSystemId, device);
+        devicesInProximity->insert_or_assign(windowSystemId, device);
     else
         devicesInProximity->remove(windowSystemId);
 }

tests/auto/corelib/tools/qflatmap/tst_qflatmap.cpp

@@ -53,7 +53,7 @@ private slots:
     void iterators();
     void statefulComparator();
     void transparency();
-    void try_emplace();
+    void try_emplace_and_insert_or_assign();
     void viewIterators();
     void varLengthArray();
 };
@@ -428,7 +428,7 @@ void tst_QFlatMap::transparency()
     QCOMPARE(m.lower_bound(sv3).value(), "dree");
 }
 
-void tst_QFlatMap::try_emplace()
+void tst_QFlatMap::try_emplace_and_insert_or_assign()
 {
     using Map = QFlatMap<QByteArray, QByteArray>;
 
@@ -457,12 +457,32 @@ void tst_QFlatMap::try_emplace()
         Map m;
         QVERIFY(m.try_emplace(lvalue(foo), lvalue(qqq)).second);
         CHECKS();
+        QVERIFY(!m.insert_or_assign(lvalue(foo), lvalue(foo)).second);
+        QCOMPARE(m.value(foo), foo);
+    }
+
+    {
+        Map m;
+        QVERIFY(m.insert_or_assign(lvalue(foo), lvalue(qqq)).second);
+        CHECKS();
+        QVERIFY(!m.try_emplace(lvalue(foo), lvalue(foo)).second);
+        QCOMPARE(m.value(foo), qqq);
     }
 
     {
         Map m;
         QVERIFY(m.try_emplace(lvalue(foo), rvalue(qqq)).second);
         CHECKS();
+        QVERIFY(!m.insert_or_assign(lvalue(foo), rvalue(foo)).second);
+        QCOMPARE(m.value(foo), foo);
+    }
+
+    {
+        Map m;
+        QVERIFY(m.insert_or_assign(lvalue(foo), rvalue(qqq)).second);
+        CHECKS();
+        QVERIFY(!m.try_emplace(lvalue(foo), rvalue(foo)).second);
+        QCOMPARE(m.value(foo), qqq);
     }
 
     {
@@ -477,18 +497,49 @@ void tst_QFlatMap::try_emplace()
         QVERIFY(m.try_emplace(lvalue(foo), sb(qqq)).second);
         QCOMPARE(m.value(foo), qqq);
         CHECKS();
+        QVERIFY(!m.insert_or_assign(lvalue(foo), sb(foo)).second);
+        QCOMPARE(m.value(foo), foo);
+    }
+
+    {
+        Map m;
+        QVERIFY(m.insert_or_assign(lvalue(foo), sb(qqq)).second);
+        QCOMPARE(m.value(foo), qqq);
+        CHECKS();
+        QVERIFY(!m.try_emplace(lvalue(foo), sb(foo)).second);
+        QCOMPARE(m.value(foo), qqq);
     }
 
     {
         Map m;
         QVERIFY(m.try_emplace(rvalue(foo), lvalue(qqq)).second);
         CHECKS();
+        QVERIFY(!m.insert_or_assign(rvalue(foo), lvalue(foo)).second);
+        QCOMPARE(m.value(foo), foo);
+    }
+
+    {
+        Map m;
+        QVERIFY(m.insert_or_assign(rvalue(foo), lvalue(qqq)).second);
+        CHECKS();
+        QVERIFY(!m.try_emplace(rvalue(foo), lvalue(foo)).second);
+        QCOMPARE(m.value(foo), qqq);
     }
 
     {
         Map m;
         QVERIFY(m.try_emplace(rvalue(foo), rvalue(qqq)).second);
         CHECKS();
+        QVERIFY(!m.insert_or_assign(rvalue(foo), rvalue(foo)).second);
+        QCOMPARE(m.value(foo), foo);
+    }
+
+    {
+        Map m;
+        QVERIFY(m.insert_or_assign(rvalue(foo), rvalue(qqq)).second);
+        CHECKS();
+        QVERIFY(!m.try_emplace(rvalue(foo), rvalue(foo)).second);
+        QCOMPARE(m.value(foo), qqq);
     }
 
     {
@@ -503,6 +554,17 @@ void tst_QFlatMap::try_emplace()
         QVERIFY(m.try_emplace(rvalue(foo), sb(qqq)).second);
         QCOMPARE(m.value(foo), qqq);
         CHECKS();
+        QVERIFY(!m.insert_or_assign(rvalue(foo), sb(foo)).second);
+        QCOMPARE(m.value(foo), foo);
+    }
+
+    {
+        Map m;
+        QVERIFY(m.insert_or_assign(rvalue(foo), sb(qqq)).second);
+        QCOMPARE(m.value(foo), qqq);
+        CHECKS();
+        QVERIFY(!m.try_emplace(rvalue(foo), sb(foo)).second);
+        QCOMPARE(m.value(foo), qqq);
     }
 #undef CHECKS
 #undef lvalue