From 8c991345847e4b050d746a3efc28ddfa7115a130 Mon Sep 17 00:00:00 2001
From: Magdalena Stojek <magdalena.stojek@qt.io>
Date: Wed, 12 Mar 2025 14:23:53 +0100
Subject: [PATCH] QDom: Fix setAttributeNode() to properly replace existing
 attributes

This fix ensures that QDomElement::setAttributeNode() correctly replaces
an existing attribute with the same name. Previously, calling
setAttributeNode() with a new attribute of the same name resulted in
both the old and new attributes being present, violating the expected
behavior described in the documentation.

Fixes: QTBUG-15125
Pick-to: 6.9 6.8 6.5
Change-Id: Ibdda37a65f6e754d9f7e68e725d3438bbb2d9e0c
Reviewed-by: Mate Barany <mate.barany@qt.io>
---
 src/xml/dom/qdom.cpp                 | 10 +++++++---
 tests/auto/xml/dom/qdom/tst_qdom.cpp | 28 ++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/src/xml/dom/qdom.cpp b/src/xml/dom/qdom.cpp
index 9daf13f377c..7bfe6cd5cc7 100644
--- a/src/xml/dom/qdom.cpp
+++ b/src/xml/dom/qdom.cpp
@@ -4123,14 +4123,18 @@ QDomAttrPrivate* QDomElementPrivate::attributeNodeNS(const QString& nsURI, const
 
 QDomAttrPrivate* QDomElementPrivate::setAttributeNode(QDomAttrPrivate* newAttr)
 {
-    QDomNodePrivate* n = m_attr->namedItem(newAttr->nodeName());
+    if (!newAttr)
+        return nullptr;
+
+    QDomNodePrivate* foundAttr = m_attr->namedItem(newAttr->nodeName());
+    if (foundAttr)
+        m_attr->removeNamedItem(newAttr->nodeName());
 
     // Referencing is done by the maps
     m_attr->setNamedItem(newAttr);
-
     newAttr->setParent(this);
 
-    return static_cast<QDomAttrPrivate *>(n);
+    return static_cast<QDomAttrPrivate *>(foundAttr);
 }
 
 QDomAttrPrivate* QDomElementPrivate::setAttributeNodeNS(QDomAttrPrivate* newAttr)
diff --git a/tests/auto/xml/dom/qdom/tst_qdom.cpp b/tests/auto/xml/dom/qdom/tst_qdom.cpp
index 8138de1fce3..2c62e6fa1a8 100644
--- a/tests/auto/xml/dom/qdom/tst_qdom.cpp
+++ b/tests/auto/xml/dom/qdom/tst_qdom.cpp
@@ -89,6 +89,7 @@ private slots:
     void normalizeAttributes() const;
     void serializeWeirdEOL() const;
     void reparentAttribute() const;
+    void replaceAttribute() const;
     void serializeNamespaces() const;
     void flagInvalidNamespaces() const;
     void flagUndeclaredNamespace() const;
@@ -1999,6 +2000,33 @@ void tst_QDom::reparentAttribute() const
     QVERIFY(attr.parentNode() == ele);
 }
 
+void tst_QDom::replaceAttribute() const
+{
+    QDomImplementation impl;
+    QDomDocument doc(impl.createDocument("", "docName", QDomDocumentType()));
+
+    QDomElement root = doc.createElement("root");
+    doc.appendChild(root);
+
+    QDomAttr attr1 = doc.createAttribute("firstAttribute");
+    attr1.setValue("true");
+    auto nullAttr = root.setAttributeNode(attr1);
+    QVERIFY(nullAttr.isNull());
+    QVERIFY(root.hasAttribute("firstAttribute"));
+    QCOMPARE(root.attributeNode("firstAttribute").value(), "true");
+
+    QDomAttr attr2 = doc.createAttribute("firstAttribute");
+    attr2.setValue("false");
+    root.setAttributeNode(attr2);
+    QCOMPARE(root.attributeNode("firstAttribute").value(), "false");
+
+    QDomAttr attr3 = doc.createAttribute("secondAttribute");
+    attr3.setValue("123");
+    root.setAttributeNode(attr3);
+    QVERIFY(root.hasAttribute("secondAttribute"));
+    QCOMPARE(root.attributeNode("secondAttribute").value(), "123");
+}
+
 void tst_QDom::serializeNamespaces() const
 {
     const char *const input = "<doc xmlns:b='http://example.com/'>"