Support Arrays.asList in GenericData cloning

Resolves #293

Author: ejona86

google-http-client/src/main/java/com/google/api/client/util/Data.java

@@ -23,6 +23,7 @@
 import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashSet;
@@ -216,6 +217,14 @@ public static <T> T clone(T data) {
       copy = (T) Array.newInstance(dataClass.getComponentType(), Array.getLength(data));
     } else if (data instanceof ArrayMap<?, ?>) {
       copy = (T) ((ArrayMap<?, ?>) data).clone();
+    } else if ("java.util.Arrays$ArrayList".equals(dataClass.getName())) {
+      // Arrays$ArrayList does not have a zero-arg constructor, so it has to handled specially.
+      // Although it appears as an Object[], arrayCopy shares the same type as the array originally
+      // passed to Arrays.asList() because Arrays$ArrayList uses clone() to create it.
+      Object[] arrayCopy = ((List<?>) data).toArray();
+      deepCopy(arrayCopy, arrayCopy);
+      copy = (T) Arrays.asList(arrayCopy);
+      return copy;
     } else {
       copy = (T) Types.newInstance(dataClass);
     }

google-http-client/src/test/java/com/google/api/client/util/DataTest.java

@@ -116,6 +116,22 @@ public void testClone_arrayMap() {
     assertEquals(map, Data.clone(map));
   }
 
+  public void testClone_ArraysAsList() {
+    List<Object> orig = Arrays.<Object>asList("a", "b", "c", new ArrayList<Object>());
+    List<Object> result = Data.clone(orig);
+    assertTrue(orig != result);
+    assertEquals(orig, result);
+    assertTrue(orig.get(3) != result.get(3));
+
+    List list = Data.clone(Arrays.asList(new String[] {"a", "b", "c"}));
+    try {
+      list.set(0, new Object());
+      fail("Cloned list should be backed by String[], not Object[]");
+    } catch (ArrayStoreException e) {
+      // expected
+    }
+  }
+
   public void testNewCollectionInstance() throws Exception {
     assertEquals(ArrayList.class, Data.newCollectionInstance(null).getClass());
     assertEquals(ArrayList.class, Data.newCollectionInstance(String[].class).getClass());