Cursor comparison bugfix with empty cursors (and null values).

1 files changed, 8 insertions, 1 deletions

diff --git a/subprojects/store/src/main/java/tools/refinery/store/map/internal/MapCursor.java b/subprojects/store/src/main/java/tools/refinery/store/map/internal/MapCursor.java
index f874137b..50fcfcd3 100644
--- a/subprojects/store/src/main/java/tools/refinery/store/map/internal/MapCursor.java
+++ b/subprojects/store/src/main/java/tools/refinery/store/map/internal/MapCursor.java
@@ -117,7 +117,12 @@ public class MapCursor<K, V> implements Cursor<K, V> {
          * same position.
          */
         public static <K, V> int compare(MapCursor<K, V> cursor1, MapCursor<K, V> cursor2) {
-                // two cursors are equally deep
+                // Checking the state of the cursors
+                if(!cursor1.isTerminated() && cursor2.isTerminated()) return -1;
+                else if(cursor1.isTerminated() && !cursor2.isTerminated()) return 1;
+                else if(cursor1.isTerminated() && cursor2.isTerminated()) return 0;
+
+                // If the state does not determine the order, then compare @nodeIndexStack.
                 Iterator<Integer> stack1 = cursor1.nodeIndexStack.descendingIterator();
                 Iterator<Integer> stack2 = cursor2.nodeIndexStack.descendingIterator();
                 if (stack1.hasNext()) {
@@ -137,6 +142,8 @@ public class MapCursor<K, V> implements Cursor<K, V> {
                         // stack 2 has more element, thus stack 2 is deeper
                         return 1;
                 }
+
+                // two cursors are equally deep decide by data index
                 return Integer.compare(cursor1.dataIndex, cursor2.dataIndex);
         }
 }