OAK-11607 the ordered children property can be null; make the test more robust

Author: joerghoh

oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/tree/impl/OrderedChildnameIterable.java

@@ -1,6 +1,7 @@
 package org.apache.jackrabbit.oak.plugins.tree.impl;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
@@ -41,7 +42,7 @@ public class OrderedChildnameIterator implements Iterator<String> {
         private Iterator<String> nonOrderedChildrenIterator = null;
 
         public OrderedChildnameIterator (Iterable<String> orderedChildren, Iterable<String> allChildren) {
-            this.orderedChildren = orderedChildren.iterator();
+            this.orderedChildren = orderedChildren == null ? Collections.emptyIterator() : orderedChildren.iterator();
             this.allChildren = allChildren.iterator();
             nextResult = getNextElement();
         }

oak-core/src/test/java/org/apache/jackrabbit/oak/security/authorization/evaluation/ChildOrderPropertyTest.java

@@ -21,6 +21,7 @@
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Set;
 
@@ -32,6 +33,7 @@
 import org.apache.jackrabbit.oak.commons.collections.SetUtils;
 import org.apache.jackrabbit.oak.plugins.tree.TreeConstants;
 import org.apache.jackrabbit.oak.spi.security.privilege.PrivilegeConstants;
+import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 
@@ -98,7 +100,11 @@ public void testChildOrderWithoutPropertyReadAccess() throws Exception {
         assertFalse(aTree.hasProperty(JcrConstants.JCR_PRIMARYTYPE));
 
         List<String> expected = List.of("/a/bb", "/a/b");
-        Iterable<String> childPaths = IterableUtils.transform(aTree.getChildren(), input -> input.getPath());
-        assertTrue(childPaths.toString(), IterableUtils.elementsEqual(expected, childPaths));
+
+        // Collect actual paths into a list
+        List<String> actual = new ArrayList<>();
+        aTree.getChildren().forEach( c -> actual.add(c.getPath()));
+
+        assertEquals("Child order should be maintained", expected, actual);
     }
 }