JENA-369: Correct handling for the case of union-of-one

lingya · Jun 25, 2017 · f9c0746 · f9c0746
1 parent 32e5f20
commit f9c0746
Showing 1 changed file with 8 additions and 2 deletions.
diff --git a/jena-arq/src/main/java/org/apache/jena/sparql/serializer/FormatterElement.java b/jena-arq/src/main/java/org/apache/jena/sparql/serializer/FormatterElement.java
@@ -243,10 +243,16 @@ public void visit(ElementData el) {
 
     @Override
     public void visit(ElementUnion el) {
-        if ( el.getElements().size() <= 1 ) {
-        	// If this is an element of just one (or none), just do it in-place
+        if ( el.getElements().size() == 0 ) {
+        	// If this is a union of zero elements, do nothing.
             return ;
         }
+
+        if ( el.getElements().size() == 0 ) {
+            // If this is a union of one elements, put in a {}-group 
+            visitAsGroup(el.getElements().get(0));
+            return;
+        }
 
         if ( UNION_MARKERS ) {
             out.print("{");