QMetaContainer: Consistently coerce types

The high-level iterable interfaces should coerce the types of most
QVariants passed to the expected ones. To do this, move the type
coercion code into qvariant.{h|cpp} so that it is available to the
QVariantRef specializations.

The exception are variants passed to the find() functions of associative
iterables. Here, we should not coerce values we cannot convert to the
default-constructed keys. Instead we return end() in such cases.

Fixes: QTBUG-87687
Change-Id: I0bd4e5c4e4e270dd3bf36cb3fb115794828077f2
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

9 files changed, 86 insertions, 97 deletions

diff --git a/src/corelib/kernel/kernel.pri b/src/corelib/kernel/kernel.pri
index 518caa4494..0b6c8cbc76 100644
--- a/src/corelib/kernel/kernel.pri
+++ b/src/corelib/kernel/kernel.pri
@@ -75,7 +75,6 @@ SOURCES += \
         kernel/qvariant.cpp \
         kernel/qcoreglobaldata.cpp \
         kernel/qiterable.cpp \
-        kernel/qiterable_p.cpp \
         kernel/qsequentialiterable.cpp \
         kernel/qassociativeiterable.cpp \
         kernel/qsharedmemory.cpp \
diff --git a/src/corelib/kernel/qassociativeiterable.cpp b/src/corelib/kernel/qassociativeiterable.cpp
index 780ae35a42..5e30ae291e 100644
--- a/src/corelib/kernel/qassociativeiterable.cpp
+++ b/src/corelib/kernel/qassociativeiterable.cpp
@@ -187,40 +187,46 @@ QVariantConstPointer QAssociativeConstIterator::operator->() const
 
 /*!
     Retrieves a const_iterator pointing to the element at the given \a key, or
-    the end of the container if that key does not exist.
+    the end of the container if that key does not exist. If the \a key isn't
+    convertible to the expected type, the end of the container is returned.
  */
 QAssociativeIterable::const_iterator QAssociativeIterable::find(const QVariant &key) const
 {
     const QMetaAssociation meta = metaContainer();
-    QVariant converted = key;
-    const void *keyData = QIterablePrivate::coerceType(converted, meta.keyMetaType());
-    return const_iterator(QConstIterator(
-                this, meta.createConstIteratorAtKey(constIterable(), keyData)));
+    QtPrivate::QVariantTypeCoercer coercer;
+    if (const void *keyData = coercer.convert(key, meta.keyMetaType())) {
+        return const_iterator(QConstIterator(this, meta.createConstIteratorAtKey(
+                                                 constIterable(), keyData)));
+    }
+    return constEnd();
 }
 
 /*!
     Retrieves an iterator pointing to the element at the given \a key, or
-    the end of the container if that key does not exist.
+    the end of the container if that key does not exist. If the \a key isn't
+    convertible to the expected type, the end of the container is returned.
  */
 QAssociativeIterable::iterator QAssociativeIterable::mutableFind(const QVariant &key)
 {
     const QMetaAssociation meta = metaContainer();
-    QVariant converted = key;
-    const void *keyData = QIterablePrivate::coerceType(converted, meta.keyMetaType());
-    return iterator(QIterator(this, meta.createIteratorAtKey(mutableIterable(), keyData)));
+    QtPrivate::QVariantTypeCoercer coercer;
+    if (const void *keyData = coercer.convert(key, meta.keyMetaType()))
+        return iterator(QIterator(this, meta.createIteratorAtKey(mutableIterable(), keyData)));
+    return mutableEnd();
 }
 
 /*!
-    Retrieves the mapped value at the given \a key, or an invalid QVariant
-    if the key does not exist.
+    Retrieves the mapped value at the given \a key, or a default-constructed
+    QVariant of the mapped type, if the key does not exist. If the \a key is not
+    convertible to the key type, the mapped value associated with the
+    default-constructed key is returned.
  */
 QVariant QAssociativeIterable::value(const QVariant &key) const
 {
     const QMetaAssociation meta = metaContainer();
-    QVariant converted = key;
-    const void *keyData = QIterablePrivate::coerceType(converted, meta.keyMetaType());
+    QtPrivate::QVariantTypeCoercer coercer;
     QVariant result(QMetaType(meta.mappedMetaType()));
-    meta.mappedAtKey(constIterable(), keyData, result.data());
+    meta.mappedAtKey(constIterable(), coercer.coerce(key, meta.keyMetaType()), result.data());
     return result;
 }
 
diff --git a/src/corelib/kernel/qassociativeiterable.h b/src/corelib/kernel/qassociativeiterable.h
index 8412dc86fd..ba20af0327 100644
--- a/src/corelib/kernel/qassociativeiterable.h
+++ b/src/corelib/kernel/qassociativeiterable.h
@@ -163,14 +163,15 @@ inline QVariantRef<QAssociativeIterator>::operator QVariant() const
 {
     if (m_pointer == nullptr)
         return QVariant();
+
     const auto metaAssociation = m_pointer->metaContainer();
-    QMetaType metaType(metaAssociation.mappedMetaType());
+    const QMetaType metaType(metaAssociation.mappedMetaType());
     if (!metaType.isValid())
         return m_pointer->key();
 
     QVariant v(metaType);
-    void *dataPtr = metaType == QMetaType::fromType<QVariant>() ? &v : v.data();
-    metaAssociation.mappedAtIterator(m_pointer->constIterator(), dataPtr);
+    metaAssociation.mappedAtIterator(m_pointer->constIterator(),
+                                     metaType == QMetaType::fromType<QVariant>() ? &v : v.data());
     return v;
 }
 
@@ -180,11 +181,15 @@ inline QVariantRef<QAssociativeIterator> &QVariantRef<QAssociativeIterator>::ope
 {
     if (m_pointer == nullptr)
         return *this;
-    const QMetaType metaType(m_pointer->metaContainer().mappedMetaType());
-    const void *dataPtr = metaType == QMetaType::fromType<QVariant>()
-            ? &value
-            : value.constData();
-    m_pointer->metaContainer().setMappedAtIterator(m_pointer->constIterator(), dataPtr);
+
+    const auto metaAssociation = m_pointer->metaContainer();
+    const QMetaType metaType(metaAssociation.mappedMetaType());
+    if (metaType.isValid()) {
+        QtPrivate::QVariantTypeCoercer coercer;
+        metaAssociation.setMappedAtIterator(m_pointer->constIterator(),
+                                            coercer.coerce(value, metaType));
+    }
+
     return *this;
 }
 
diff --git a/src/corelib/kernel/qiterable_p.cpp b/src/corelib/kernel/qiterable_p.cpp
deleted file mode 100644
index ea569cebd5..0000000000
--- a/src/corelib/kernel/qiterable_p.cpp
+++ /dev/null
@@ -1,63 +0,0 @@
-/****************************************************************************
-**
-** Copyright (C) 2020 The Qt Company Ltd.
-** Contact: https://www.qt.io/licensing/
-**
-** This file is part of the QtCore module of the Qt Toolkit.
-**
-** $QT_BEGIN_LICENSE:LGPL$
-** Commercial License Usage
-** Licensees holding valid commercial Qt licenses may use this file in
-** accordance with the commercial license agreement provided with the
-** Software or, alternatively, in accordance with the terms contained in
-** a written agreement between you and The Qt Company. For licensing terms
-** and conditions see https://www.qt.io/terms-conditions. For further
-** information use the contact form at https://www.qt.io/contact-us.
-**
-** GNU Lesser General Public License Usage
-** Alternatively, this file may be used under the terms of the GNU Lesser
-** General Public License version 3 as published by the Free Software
-** Foundation and appearing in the file LICENSE.LGPL3 included in the
-** packaging of this file. Please review the following information to
-** ensure the GNU Lesser General Public License version 3 requirements
-** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
-**
-** GNU General Public License Usage
-** Alternatively, this file may be used under the terms of the GNU
-** General Public License version 2.0 or (at your option) the GNU General
-** Public license version 3 or any later version approved by the KDE Free
-** Qt Foundation. The licenses are as published by the Free Software
-** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
-** included in the packaging of this file. Please review the following
-** information to ensure the GNU General Public License requirements will
-** be met: https://www.gnu.org/licenses/gpl-2.0.html and
-** https://www.gnu.org/licenses/gpl-3.0.html.
-**
-** $QT_END_LICENSE$
-**
-****************************************************************************/
-
-#include <QtCore/private/qiterable_p.h>
-
-QT_BEGIN_NAMESPACE
-
-namespace QIterablePrivate {
-
-const void *coerceType(QVariant &value, const QMetaType &type)
-{
-    if (type == QMetaType::fromType<QVariant>()) {
-        return &value;
-    } else if (type == value.metaType()) {
-        return value.constData();
-    } else if (value.canConvert(type)) {
-        value.convert(type);
-        return value.constData();
-    }
-
-    value = QVariant(type);
-    return value.constData();
-}
-
-} // namespace QIterablePrivate
-
-QT_END_NAMESPACE
diff --git a/src/corelib/kernel/qiterable_p.h b/src/corelib/kernel/qiterable_p.h
index 33b190a59a..979ef49b18 100644
--- a/src/corelib/kernel/qiterable_p.h
+++ b/src/corelib/kernel/qiterable_p.h
@@ -58,8 +58,6 @@ QT_BEGIN_NAMESPACE
 
 namespace QIterablePrivate {
 
-const void *coerceType(QVariant &value, const QMetaType &type);
-
 template<typename Callback>
 static QVariant retrieveElement(const QMetaType &type, Callback callback)
 {
diff --git a/src/corelib/kernel/qsequentialiterable.cpp b/src/corelib/kernel/qsequentialiterable.cpp
index 6ce41a1edf..054d97d90f 100644
--- a/src/corelib/kernel/qsequentialiterable.cpp
+++ b/src/corelib/kernel/qsequentialiterable.cpp
@@ -106,8 +106,8 @@ QT_BEGIN_NAMESPACE
  */
 void QSequentialIterable::addValue(const QVariant &value, Position position)
 {
-    QVariant converted = value;
-    const void *valuePtr = QIterablePrivate::coerceType(converted, metaContainer().valueMetaType());
+    QtPrivate::QVariantTypeCoercer coercer;
+    const void *valuePtr = coercer.coerce(value, metaContainer().valueMetaType());
 
     switch (position) {
     case AtBegin:
@@ -181,8 +181,8 @@ QVariant QSequentialIterable::at(qsizetype idx) const
 */
 void QSequentialIterable::set(qsizetype idx, const QVariant &value)
 {
-    QVariant converted = value;
-    const void *dataPtr = QIterablePrivate::coerceType(converted, metaContainer().valueMetaType());
+    QtPrivate::QVariantTypeCoercer coercer;
+    const void *dataPtr = coercer.coerce(value, metaContainer().valueMetaType());
 
     const QMetaSequence meta = metaContainer();
     if (meta.canSetValueAtIndex()) {
diff --git a/src/corelib/kernel/qsequentialiterable.h b/src/corelib/kernel/qsequentialiterable.h
index 5851439316..a5a22b55df 100644
--- a/src/corelib/kernel/qsequentialiterable.h
+++ b/src/corelib/kernel/qsequentialiterable.h
@@ -172,11 +172,11 @@ inline QVariantRef<QSequentialIterator> &QVariantRef<QSequentialIterator>::opera
 {
     if (m_pointer == nullptr)
         return *this;
-    const QMetaType metaType(m_pointer->metaContainer().valueMetaType());
-    const void *dataPtr = metaType == QMetaType::fromType<QVariant>()
-            ? &value
-            : value.constData();
-    m_pointer->metaContainer().setValueAtIterator(m_pointer->constIterator(), dataPtr);
+
+    QtPrivate::QVariantTypeCoercer coercer;
+    m_pointer->metaContainer().setValueAtIterator(
+                m_pointer->constIterator(),
+                coercer.coerce(value, m_pointer->metaContainer().valueMetaType()));
     return *this;
 }
 
diff --git a/src/corelib/kernel/qvariant.cpp b/src/corelib/kernel/qvariant.cpp
index 09c3eee6ea..849ed6e6ef 100644
--- a/src/corelib/kernel/qvariant.cpp
+++ b/src/corelib/kernel/qvariant.cpp
@@ -2729,6 +2729,38 @@ QDebug operator<<(QDebug dbg, const QVariant::Type p)
 */
 
 /*!
+    \internal
+ */
+const void *QtPrivate::QVariantTypeCoercer::convert(const QVariant &value, const QMetaType &type)
+{
+    if (type == QMetaType::fromType<QVariant>())
+        return &value;
+
+    if (type == value.metaType())
+        return value.constData();
+
+    if (value.canConvert(type)) {
+        converted = value;
+        if (converted.convert(type))
+            return converted.constData();
+    }
+
+    return nullptr;
+}
+
+/*!
+    \internal
+ */
+const void *QtPrivate::QVariantTypeCoercer::coerce(const QVariant &value, const QMetaType &type)
+{
+    if (const void *result = convert(value, type))
+        return result;
+
+    converted = QVariant(type);
+    return converted.constData();
+}
+
+/*!
     \class QVariantRef
     \since 6.0
     \inmodule QtCore
diff --git a/src/corelib/kernel/qvariant.h b/src/corelib/kernel/qvariant.h
index 40d3d5c3b1..aa74aaa18f 100644
--- a/src/corelib/kernel/qvariant.h
+++ b/src/corelib/kernel/qvariant.h
@@ -605,6 +605,18 @@ template<> inline QVariant qvariant_cast<QVariant>(const QVariant &v)
 Q_CORE_EXPORT QDebug operator<<(QDebug, const QVariant::Type);
 #endif
 
+namespace QtPrivate {
+class Q_CORE_EXPORT QVariantTypeCoercer
+{
+public:
+    const void *convert(const QVariant &value, const QMetaType &type);
+    const void *coerce(const QVariant &value, const QMetaType &type);
+
+private:
+    QVariant converted;
+};
+}
+
 template<typename Pointer>
 class QVariantRef
 {