QDomDocument::setContent: Open device if necessary

This restores the Qt 5 behavior in Qt 6, but prepares for disabling it
in Qt 7. We want to deprecate the current behavior, as it makes it
unclear who is responsible for calling close.

Fixes: QTBUG-97747
Pick-to: 6.2
Change-Id: I2c99eb96667e784576d8850085068ca334d75b16
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

src/xml/dom/qdom.cpp

@@ -6197,12 +6197,28 @@ bool QDomDocument::setContent(const QByteArray &data, bool namespaceProcessing,
 
     This function reads the XML document from the IO device \a dev, returning
     true if the content was successfully parsed; otherwise returns \c false.
+
+    \note This method will try to open \a dev in read-only mode if it is not
+    already open. In that case, the caller is responsible for calling close.
+    This will change in Qt 7, which will no longer open \a dev. Applications
+    shoul therefore open the device themselves before calling setContent.
 */
 bool QDomDocument::setContent(QIODevice* dev, bool namespaceProcessing, QString *errorMsg, int *errorLine, int *errorColumn)
 {
     if (!impl)
         impl = new QDomDocumentPrivate();
 
+#if QT_VERSION < QT_VERSION_CHECK(7, 0, 0)
+    if (!dev->isOpen()) {
+        qWarning("QDomDocument called with unopened QIODevice. "
+                 "This will not be supported in future Qt versions");
+        if (!dev->open(QIODevice::ReadOnly)) {
+            qWarning("QDomDocument::setContent: Failed to open device");
+            return false;
+        }
+    }
+#endif
+
     QXmlStreamReader streamReader(dev);
     streamReader.setNamespaceProcessing(namespaceProcessing);
     return IMPL->setContent(&streamReader, namespaceProcessing, errorMsg, errorLine, errorColumn);

tests/auto/xml/dom/qdom/tst_qdom.cpp

@@ -111,6 +111,7 @@ private slots:
     void checkIntOverflow() const;
     void setContentWhitespace() const;
     void setContentWhitespace_data() const;
+    void setContentUnopenedQIODevice() const;
 
     void taskQTBUG4595_dontAssertWhenDocumentSpecifiesUnknownEncoding() const;
     void cloneDTD_QTBUG8398() const;
@@ -1919,6 +1920,23 @@ void tst_QDom::setContentWhitespace_data() const
     QTest::newRow("data25") << QString::fromLatin1("\t\t\t\t<?xml version='1.0' ?><e/>")  << false;
 }
 
+void tst_QDom::setContentUnopenedQIODevice() const
+{
+    QByteArray data("<foo>bar</foo>");
+    QBuffer buffer(&data);
+
+    QDomDocument doc;
+
+    QTest::ignoreMessage(QtWarningMsg,
+                         "QDomDocument called with unopened QIODevice. "
+                         "This will not be supported in future Qt versions");
+
+    // Note: the check below is expected to fail in Qt 7.
+    // Fix the test and remove the obsolete code from setContent().
+    QVERIFY(doc.setContent(&buffer, true));
+    QCOMPARE(doc.toString().trimmed(), data);
+}
+
 void tst_QDom::taskQTBUG4595_dontAssertWhenDocumentSpecifiesUnknownEncoding() const
 {
     QString xmlWithUnknownEncoding("<?xml version='1.0' encoding='unknown-encoding'?>"