Correct behavior of $append function. #37

The discrepancy is caused by a (legacy) condition in the $append function.
This was introduced to hide an older parser issue (which was fixed in the meantime) so it is no longer needed

src/main/java/com/dashjoin/jsonata/Functions.java

@@ -2080,19 +2080,13 @@ public static Object append(Object arg1, Object arg2) {
         if (!(arg2 instanceof List)) {
             arg2 = new JList<>(Arrays.asList(arg2));
         }
-        // else
-        //     // Arg2 was a list: add it as a list element (don't flatten)
-        //     ((List)arg1).add((List)arg2);
 
         // Shortcut:
         if (((List)arg1).isEmpty() && (arg2 instanceof Utils.RangeList))
             return arg2;
 
         arg1 = new JList<>((List)arg1); // create a new copy!
-        if (arg2 instanceof JList && ((JList)arg2).cons)
-            ((List)arg1).add(arg2);
-        else
-            ((List)arg1).addAll((List)arg2);
+        ((List)arg1).addAll((List)arg2);
         return arg1;
     }
 

src/test/java/com/dashjoin/jsonata/ArrayTest.java

@@ -4,12 +4,10 @@
 import static java.util.Arrays.asList;
 import static java.util.Map.of;
 import static org.junit.jupiter.api.Assertions.assertEquals;
-import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
 
 public class ArrayTest {
 
-  @Disabled
   @Test
   public void testArray() {
     Jsonata expr1 = jsonata("{'key': $append($.[{'x': 'y'}],$.[{'a': 'b'}])}");