[bugfix] Map constructor should not allow entries with duplicate keys.

Closes #2203

Author: adamretter

src/org/exist/xquery/ErrorCodes.java

@@ -131,8 +131,9 @@ public class ErrorCodes {
             "Bind the prefix xmlns to any namespace URI.\n" +
             "Bind a prefix to the namespace URI http://www.w3.org/2000/xmlns/.\n" +
             "Bind any prefix (including the empty prefix) to a zero-length namespace URI.");
-    public static final ErrorCode XQDY0138 = new W3CErrorCode("XQDY0138", "Position n does not exist in this array");
     public static final ErrorCode XQDY0102 = new W3CErrorCode("XQDY0102", "If the name of an element in an element constructor is in no namespace, creating a default namespace for that element using a computed namespace constructor is an error.");
+    public static final ErrorCode XQDY0137 = new W3CErrorCode("XQDY0137", "No two keys in a map may have the same key value");
+    public static final ErrorCode XQDY0138 = new W3CErrorCode("XQDY0138", "Position n does not exist in this array");
 
     /* XQuery 1.0 and XPath 2.0 Functions and Operators http://www.w3.org/TR/xpath-functions/#error-summary */
     public static final ErrorCode FOER0000 = new W3CErrorCode("FOER0000", "Unidentified error.");

src/org/exist/xquery/functions/map/MapExpr.java

@@ -52,6 +52,9 @@ public Sequence eval(Sequence contextSequence, final Item contextItem) throws XP
             }
             final AtomicValue atomic = key.itemAt(0).atomize();
             final Sequence value = mapping.value.eval(contextSequence);
+            if (map.contains(atomic)) {
+                throw new XPathException(this, ErrorCodes.XQDY0137, "Key \"" + atomic.getStringValue() + "\" already exists in map.");
+            }
             map.add(atomic, value);
         }
         return map;