Fix memory leak in wxXmlNode::operator=().

We must delete all children and attributes in the node being overwritten and
not just the first one of each.

Add a unit test exercising this code to be able to check that valgrind doesn't
report memory leak any more after the fix.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73990 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

tests/xml/xmltest.cpp

@@ -82,6 +82,7 @@ private:
         CPPUNIT_TEST( DetachRoot );
         CPPUNIT_TEST( AppendToProlog );
         CPPUNIT_TEST( SetRoot );
+        CPPUNIT_TEST( CopyNode );
     CPPUNIT_TEST_SUITE_END();
 
     void InsertChild();
@@ -93,6 +94,7 @@ private:
     void DetachRoot();
     void AppendToProlog();
     void SetRoot();
+    void CopyNode();
 
     DECLARE_NO_COPY_CLASS(XmlTestCase)
 };
@@ -469,3 +471,40 @@ void XmlTestCase::SetRoot()
     doc.SetRoot(root);
     CPPUNIT_ASSERT( doc.IsOk() );
 }
+
+void XmlTestCase::CopyNode()
+{
+    const char *xmlText =
+"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
+"<root>\n"
+"  <first><sub1/><sub2/><sub3/></first>\n"
+"  <second/>\n"
+"</root>\n"
+    ;
+    wxXmlDocument doc;
+    wxStringInputStream sis(xmlText);
+    CPPUNIT_ASSERT( doc.Load(sis) );
+
+    wxXmlNode* const root = doc.GetRoot();
+    CPPUNIT_ASSERT( root );
+
+    wxXmlNode* const first = root->GetChildren();
+    CPPUNIT_ASSERT( first );
+
+    wxXmlNode* const second = first->GetNext();
+    CPPUNIT_ASSERT( second );
+
+    *first = *second;
+
+    wxStringOutputStream sos;
+    CPPUNIT_ASSERT( doc.Save(sos) );
+
+    const char *xmlTextResult =
+"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n"
+"<root>\n"
+"  <second/>\n"
+"  <second/>\n"
+"</root>\n"
+    ;
+    CPPUNIT_ASSERT_EQUAL( xmlTextResult, sos.GetString() );
+}