QCborMap: remove the optimization not to detach from non-const find()

All our tests were find() == end() or !=, which depends on the
evaluation order of the arguments to operator==(). If end() is called
first, then the detach happens before find() and all is well. But if
find() is called first, it may return end() before end() detaches.

[ChangeLog][QCborMap] Fixed a bug that could cause the iterator returned
from a failing key search with find() not to match end(). Now, every
call to find() will detach in shared QCborMaps; to avoid this, use
constFind() and constEnd().

Fixes: QTBUG-84583
Pick-to: 5.15 5.12
Change-Id: I552d244076a447ab92d7fffd161793496a8d03a8
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/corelib/serialization/qcbormap.cpp

@@ -834,9 +834,8 @@ QCborValueRef QCborMap::operator[](const QCborValue &key)
  */
 QCborMap::iterator QCborMap::find(qint64 key)
 {
+    detach();
     auto it = constFind(key);
-    if (it != constEnd())
-        detach();
     return { d.data(), it.item.i };
 }
 
@@ -860,9 +859,8 @@ QCborMap::iterator QCborMap::find(qint64 key)
  */
 QCborMap::iterator QCborMap::find(QLatin1String key)
 {
+    detach();
     auto it = constFind(key);
-    if (it != constEnd())
-        detach();
     return { d.data(), it.item.i };
 }
 
@@ -886,9 +884,8 @@ QCborMap::iterator QCborMap::find(QLatin1String key)
  */
 QCborMap::iterator QCborMap::find(const QString & key)
 {
+    detach();
     auto it = constFind(key);
-    if (it != constEnd())
-        detach();
     return { d.data(), it.item.i };
 }
 
@@ -912,9 +909,8 @@ QCborMap::iterator QCborMap::find(const QString & key)
  */
 QCborMap::iterator QCborMap::find(const QCborValue &key)
 {
+    detach();
     auto it = constFind(key);
-    if (it != constEnd())
-        detach();
     return { d.data(), it.item.i };
 }
 

tests/auto/corelib/serialization/qcborvalue/tst_qcborvalue.cpp

@@ -63,6 +63,7 @@ private slots:
     void arrayDefaultInitialization();
     void arrayEmptyInitializerList();
     void arrayEmptyDetach();
+    void arrayNonEmptyDetach();
     void arrayInitializerList();
     void arrayMutation();
     void arrayMutateWithCopies();
@@ -78,6 +79,7 @@ private slots:
     void mapDefaultInitialization();
     void mapEmptyInitializerList();
     void mapEmptyDetach();
+    void mapNonEmptyDetach();
     void mapSimpleInitializerList();
     void mapMutation();
     void mapMutateWithCopies();
@@ -657,6 +659,66 @@ void tst_QCborValue::mapEmptyDetach()
     QCOMPARE(m2, m);
 }
 
+void tst_QCborValue::arrayNonEmptyDetach()
+{
+    QCborArray a;
+    a.append(1);
+    a.append(2);
+
+    QCOMPARE(a.first(), 1);
+    QCOMPARE(a.last(), 2);
+    QVERIFY(!a.contains(3));
+    QVERIFY(a.constBegin() != a.constEnd());
+    QVERIFY(a.begin() != a.end());
+
+    // now the same, with an active copy
+    { QCborArray copy(a); QCOMPARE(a.first(), 1); }
+    { QCborArray copy(a); QCOMPARE(a.last(), 2); }
+    { QCborArray copy(a); QVERIFY(!a.contains(3)); }
+    { QCborArray copy(a); QVERIFY(a.constBegin() != a.constEnd()); }
+    { QCborArray copy(a); QVERIFY(a.begin() != a.end()); }
+}
+
+void tst_QCborValue::mapNonEmptyDetach()
+{
+    QCborMap m;
+    m.insert(1, {});
+    m.insert(2, nullptr);
+    QVERIFY(!m.contains(3));
+    QVERIFY(m.constBegin() != m.constEnd());
+    QVERIFY(m.begin() != m.end());
+    // test all 4 overloads of find()
+    QVERIFY(m.constFind(3) == m.constEnd());
+    QVERIFY(m.constFind(QLatin1String("3")) == m.constEnd());
+    QVERIFY(m.constFind(QString("3")) == m.constEnd());
+    QVERIFY(m.constFind(QCborValue(3)) == m.constEnd());
+    QVERIFY(m.find(3) == m.end());
+    QVERIFY(m.find(QLatin1String("3")) == m.end());
+    QVERIFY(m.find(QString("3")) == m.end());
+    QVERIFY(m.find(QCborValue(3)) == m.end());
+    { auto it = m.find(3); QVERIFY(it == m.end()); }
+    { auto it = m.find(QLatin1String("3")); QVERIFY(it == m.end()); }
+    { auto it = m.find(QString("3")); QVERIFY(it == m.end()); }
+    { auto it = m.find(QCborValue(3)); QVERIFY(it == m.end()); }
+
+    // now the same, with an active copy
+    { QCborMap copy(m); QVERIFY(!m.contains(3)); }
+    { QCborMap copy(m); QVERIFY(m.constBegin() != m.constEnd()); }
+    { QCborMap copy(m); QVERIFY(m.begin() != m.end()); }
+    { QCborMap copy(m); QVERIFY(m.constFind(3) == m.constEnd()); }
+    { QCborMap copy(m); QVERIFY(m.constFind(QLatin1String("3")) == m.constEnd()); }
+    { QCborMap copy(m); QVERIFY(m.constFind(QString("3")) == m.constEnd()); }
+    { QCborMap copy(m); QVERIFY(m.constFind(QCborValue(3)) == m.constEnd()); }
+    { QCborMap copy(m); QVERIFY(m.find(3) == m.end()); }
+    { QCborMap copy(m); QVERIFY(m.find(QLatin1String("3")) == m.end()); }
+    { QCborMap copy(m); QVERIFY(m.find(QString("3")) == m.end()); }
+    { QCborMap copy(m); QVERIFY(m.find(QCborValue(3)) == m.end()); }\
+    { QCborMap copy(m); auto it = m.find(3); QVERIFY(it == m.end()); }
+    { QCborMap copy(m); auto it = m.find(QLatin1String("3")); QVERIFY(it == m.end()); }
+    { QCborMap copy(m); auto it = m.find(QString("3")); QVERIFY(it == m.end()); }
+    { QCborMap copy(m); auto it = m.find(QCborValue(3)); QVERIFY(it == m.end()); }
+}
+
 void tst_QCborValue::arrayInitializerList()
 {
     QCborArray a{0, -1, false, true, nullptr, {}, 1.0};