XContentHelper.mergeDefaults with single key object list ([ { key: .. } , {key : ... } .. ] ) didn't add defaults which were not already in content

Closes #3538

src/main/java/org/elasticsearch/common/xcontent/XContentHelper.java

@@ -233,6 +233,9 @@ public class XContentHelper {
                             Map.Entry<String, Object> entry = map.entrySet().iterator().next();
                             if (processed.containsKey(entry.getKey())) {
                                 mergeDefaults(processed.get(entry.getKey()), map);
+                            } else {
+                                // put the default entries after the content ones.
+                                processed.put(entry.getKey(), map);
                             }
                         }
                         for (Map<String, Object> map : processed.values()) {

src/test/java/org/elasticsearch/test/unit/common/xcontent/support/XContentHelperTests.java

@@ -0,0 +1,69 @@
+package org.elasticsearch.test.unit.common.xcontent.support;
+/*
+ * Licensed to ElasticSearch under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. ElasticSearch licenses this
+ * file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+
+import org.elasticsearch.common.xcontent.XContentHelper;
+import org.hamcrest.Matchers;
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+
+public class XContentHelperTests {
+
+    Map<String, Object> getMap(Object... keyValues) {
+        Map<String, Object> map = new HashMap<String, Object>();
+        for (int i = 0; i < keyValues.length; i++) {
+            map.put((String) keyValues[i], keyValues[++i]);
+        }
+        return map;
+    }
+
+    Map<String, Object> getNamedMap(String name, Object... keyValues) {
+        Map<String, Object> map = getMap(keyValues);
+
+        Map<String, Object> namedMap = new HashMap<String, Object>(1);
+        namedMap.put(name, map);
+        return namedMap;
+    }
+
+    List<Object> getList(Object... values) {
+        return Arrays.asList(values);
+    }
+
+    @Test
+    public void testMergingListValuesAreMapsOfOne() {
+
+        Map<String, Object> defaults = getMap("test", getList(getNamedMap("name1", "t1", "1"), getNamedMap("name2", "t2", "2")));
+        Map<String, Object> content = getMap("test", getList(getNamedMap("name2", "t3", "3"), getNamedMap("name4", "t4", "4")));
+        Map<String, Object> expected = getMap("test",
+                getList(getNamedMap("name2", "t2", "2", "t3", "3"), getNamedMap("name4", "t4", "4"), getNamedMap("name1", "t1", "1")));
+
+        XContentHelper.mergeDefaults(content, defaults);
+
+        assertThat(content, Matchers.equalTo(expected));
+    }
+
+
+}