Fix copy-on-write consistency in updateProperties isText path (#834)

Author: cowtowncoder

src/main/java/tools/jackson/dataformat/xml/deser/XmlBeanDeserializerModifier.java

@@ -44,16 +44,18 @@ public List<BeanPropertyDefinition> updateProperties(DeserializationConfig confi
             if (acc == null) {
                 continue;
             }
-            /* First: handle "as text"? Such properties
-             * are exposed as values of 'unnamed' fields; so one way to
-             * map them is to rename property to have name ""... (and
-             * hope this does not break other parts...)
-             */
+            // First: handle "as text"? Such properties are exposed as values of 'unnamed'
+            // properties; so one way to map them is to rename property to have special
+            // name (and hope this does not break other parts...)
             Boolean b = AnnotationUtil.findIsTextAnnotation(config, intr, acc);
             if (b != null && b.booleanValue()) {
-                // unwrapped properties will appear as 'unnamed' (empty String)
                 BeanPropertyDefinition newProp = prop.withSimpleName(_cfgNameForTextValue);
                 if (newProp != prop) {
+                    // 24-Mar-2026, tatu: Create defensive copy
+                    if (changed == 0) {
+                        propDefs = new ArrayList<>(propDefs);
+                    }
+                    ++changed;
                     propDefs.set(i, newProp);
                 }
                 continue;
@@ -67,7 +69,7 @@ public List<BeanPropertyDefinition> updateProperties(DeserializationConfig confi
                         && !localName.equals(prop.getName())) {
                     // make copy-on-write as necessary
                     if (changed == 0) {
-                        propDefs = new ArrayList<BeanPropertyDefinition>(propDefs);
+                        propDefs = new ArrayList<>(propDefs);
                     }
                     ++changed;
                     propDefs.set(i, prop.withSimpleName(localName));