5 files changed, 54 insertions, 15 deletions
diff --git a/src/corelib/serialization/qcborarray.cpp b/src/corelib/serialization/qcborarray.cpp
index c8df594c07..28ae40f3df 100644
--- a/src/corelib/serialization/qcborarray.cpp
+++ b/src/corelib/serialization/qcborarray.cpp
@@ -298,7 +298,8 @@ QCborValue QCborArray::at(qsizetype i) const
     \fn QCborValueRef QCborArray::operator[](qsizetype i)
 
     Returns a reference to the QCborValue element at position \a i in the
-    array. The array must have at least \a i elements.
+    array.  Indices beyond the end of the array will grow the array, filling
+    with undefined entries, until it has an entry at the specified index.
 
     QCborValueRef has the exact same API as \l QCborValue, with one important
     difference: if you assign new values to it, this map will be updated with
@@ -312,27 +313,34 @@ QCborValue QCborArray::at(qsizetype i) const
     \fn void QCborArray::insert(qsizetype i, const QCborValue &value)
     \fn void QCborArray::insert(qsizetype i, QCborValue &&value)
 
-    Inserts \a value into the array at position \a i in this array. The array
-    must have at least \a i elements before the insertion.
+    Inserts \a value into the array at position \a i in this array. If \a i is
+    -1, the entry is appended to the array. Pads the array with invalid entries
+    if \a i is greater than the prior size of the array.
 
     \sa at(), operator[](), first(), last(), prepend(), append(),
         removeAt(), takeAt(), extract()
  */
 void QCborArray::insert(qsizetype i, const QCborValue &value)
 {
-    Q_ASSERT(size_t(i) <= size_t(size()) || i == -1);
-    if (i < 0)
+    if (i < 0) {
+        Q_ASSERT(i == -1);
         i = size();
-    detach(qMax(i + 1, size()));
+        detach(i + 1);
+    } else {
+        d = QCborContainerPrivate::grow(d.data(), i); // detaches
+    }
     d->insertAt(i, value);
 }
 
 void QCborArray::insert(qsizetype i, QCborValue &&value)
 {
-    Q_ASSERT(size_t(i) <= size_t(size()) || i == -1);
-    if (i < 0)
+    if (i < 0) {
+        Q_ASSERT(i == -1);
         i = size();
-    detach(qMax(i + 1, size()));
+        detach(i + 1);
+    } else {
+        d = QCborContainerPrivate::grow(d.data(), i); // detaches
+    }
     d->insertAt(i, value, QCborContainerPrivate::MoveContainer);
     QCborContainerPrivate::resetValue(value);
 }
diff --git a/src/corelib/serialization/qcborarray.h b/src/corelib/serialization/qcborarray.h
index 9663ee6acd..d96342cfa6 100644
--- a/src/corelib/serialization/qcborarray.h
+++ b/src/corelib/serialization/qcborarray.h
@@ -186,10 +186,15 @@ public:
     QCborValue at(qsizetype i) const;
     QCborValue first() const { return at(0); }
     QCborValue last() const { return at(size() - 1); }
-    QCborValue operator[](qsizetype i) const { return at(i); }
+    const QCborValue operator[](qsizetype i) const { return at(i); }
     QCborValueRef first() { Q_ASSERT(!isEmpty()); return begin()[0]; }
     QCborValueRef last() { Q_ASSERT(!isEmpty()); return begin()[size() - 1]; }
-    QCborValueRef operator[](qsizetype i) { Q_ASSERT(i < size()); return begin()[i]; }
+    QCborValueRef operator[](qsizetype i)
+    {
+        if (i >= size())
+            insert(i, QCborValue());
+        return begin()[i];
+    }
 
     void insert(qsizetype i, const QCborValue &value);
     void insert(qsizetype i, QCborValue &&value);
diff --git a/src/corelib/serialization/qcbormap.h b/src/corelib/serialization/qcbormap.h
index 866b7cd743..0eb163a0a8 100644
--- a/src/corelib/serialization/qcbormap.h
+++ b/src/corelib/serialization/qcbormap.h
@@ -196,14 +196,22 @@ public:
     { const_iterator it = find(key); return it == end() ? QCborValue() : it.value(); }
     QCborValue value(const QCborValue &key) const
     { const_iterator it = find(key); return it == end() ? QCborValue() : it.value(); }
-    QCborValue operator[](qint64 key) const
+#if !defined(QT_NO_CAST_FROM_ASCII) && !defined(QT_RESTRICTED_CAST_FROM_ASCII)
+    template<size_t N> QT_ASCII_CAST_WARN const QCborValue value(const char (&key)[N]) const
+    { return value(QString::fromUtf8(key, N - 1)); }
+#endif
+    const QCborValue operator[](qint64 key) const
     { const_iterator it = find(key); return it == end() ? QCborValue() : it.value(); }
-    QCborValue operator[](QLatin1String key) const
+    const QCborValue operator[](QLatin1String key) const
     { const_iterator it = find(key); return it == end() ? QCborValue() : it.value(); }
-    QCborValue operator[](const QString & key) const
+    const QCborValue operator[](const QString & key) const
     { const_iterator it = find(key); return it == end() ? QCborValue() : it.value(); }
-    QCborValue operator[](const QCborValue &key) const
+    const QCborValue operator[](const QCborValue &key) const
     { const_iterator it = find(key); return it == end() ? QCborValue() : it.value(); }
+#if !defined(QT_NO_CAST_FROM_ASCII) && !defined(QT_RESTRICTED_CAST_FROM_ASCII)
+    template<size_t N> QT_ASCII_CAST_WARN const QCborValue operator[](const char (&key)[N]) const
+    { return operator[](QString::fromUtf8(key, N - 1)); }
+#endif
     QCborValueRef operator[](qint64 key);
     QCborValueRef operator[](QLatin1String key);
     QCborValueRef operator[](const QString & key);
diff --git a/src/corelib/serialization/qcborvalue.cpp b/src/corelib/serialization/qcborvalue.cpp
index 8673628c69..935f761585 100644
--- a/src/corelib/serialization/qcborvalue.cpp
+++ b/src/corelib/serialization/qcborvalue.cpp
@@ -859,6 +859,23 @@ QCborContainerPrivate *QCborContainerPrivate::detach(QCborContainerPrivate *d, q
     return d;
 }
 
+/*!
+  Prepare for an insertion at position \a index
+
+  Detaches and ensures there are at least index entries in the array, padding
+  with Undefined as needed.
+*/
+QCborContainerPrivate *QCborContainerPrivate::grow(QCborContainerPrivate *d, qsizetype index)
+{
+    Q_ASSERT(index >= 0);
+    d = detach(d, index + 1);
+    Q_ASSERT(d);
+    int j = d->elements.size();
+    while (j < index)
+        d->append(Undefined());
+    return d;
+}
+
 // Copies or moves \a value into element at position \a e. If \a disp is
 // CopyContainer, then this function increases the reference count of the
 // container, but otherwise leaves it unmodified. If \a disp is MoveContainer,
diff --git a/src/corelib/serialization/qcborvalue_p.h b/src/corelib/serialization/qcborvalue_p.h
index 3a28707056..4050d18fa9 100644
--- a/src/corelib/serialization/qcborvalue_p.h
+++ b/src/corelib/serialization/qcborvalue_p.h
@@ -136,6 +136,7 @@ public:
     void compact(qsizetype reserved);
     static QCborContainerPrivate *clone(QCborContainerPrivate *d, qsizetype reserved = -1);
     static QCborContainerPrivate *detach(QCborContainerPrivate *d, qsizetype reserved);
+    static QCborContainerPrivate *grow(QCborContainerPrivate *d, qsizetype index);
 
     qptrdiff addByteData(const char *block, qsizetype len)
     {