add DeepCopy to ColumnVisibility

core/src/main/java/org/apache/accumulo/core/security/ColumnVisibility.java

@@ -125,6 +125,24 @@ public Node(int start, int end) {
       this.end = end;
     }
 
+    /**
+     * Creates a new node by performing a deep copy of an existing node object
+     *
+     * @param node Node object
+     * @since 2.1.4
+     */
+    public Node(Node node) {
+      List<Node> childrenNew =
+          node.children.isEmpty() ? EMPTY : new ArrayList<>(node.children.size());
+      for (Node child : node.children) {
+        childrenNew.add(new Node(child));
+      }
+      this.type = node.type;
+      this.start = node.start;
+      this.end = node.end;
+      this.children = childrenNew;
+    }
+
     public void add(Node child) {
       if (children == EMPTY) {
         children = new ArrayList<>();
@@ -505,6 +523,19 @@ public ColumnVisibility(byte[] expression) {
     validate(expression);
   }
 
+  /**
+   * Creates a new column visibility by performing a deep copy of an existing column visibility
+   * object
+   *
+   * @param visibility ColumnVisibility object
+   * @since 2.1.4
+   */
+  public ColumnVisibility(ColumnVisibility visibility) {
+    byte[] incomingExpression = visibility.expression;
+    this.expression = Arrays.copyOf(incomingExpression, incomingExpression.length);
+    this.node = new Node(visibility.node);
+  }
+
   @Override
   public String toString() {
     return "[" + new String(expression, UTF_8) + "]";

core/src/test/java/org/apache/accumulo/core/security/ColumnVisibilityTest.java

@@ -22,6 +22,7 @@
 import static org.apache.accumulo.core.security.ColumnVisibility.quote;
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotSame;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
@@ -238,6 +239,15 @@ public void testParseTreesOrdering() {
     assertTrue(flat.indexOf('b') < flat.indexOf('a'), "shortest children sort first");
   }
 
+  @Test
+  public void testDeepCopy() {
+    ColumnVisibility cv1 = new ColumnVisibility("(b&c&d)|((a|m)&y&z)|(e&f)");
+    ColumnVisibility cv2 = new ColumnVisibility(cv1);
+    assertNotSame(cv1.getExpression(), cv2.getExpression());
+    assertNotSame(cv1.getParseTree(), cv2.getParseTree());
+    assertEquals(cv1.toString(), cv2.toString());
+  }
+
   private Node parse(String s) {
     ColumnVisibility v = new ColumnVisibility(s);
     return v.getParseTree();