Respect WRITE_ENUMS_USING_TO_STRING in EnumAsIonSymbolSerializer

We don't need to make any changes for the corresponding READ_ENUMS_USING_TO_STRING because the
enum deserializer is the Jackson one which already checks for the feature.

ion/src/main/java/com/fasterxml/jackson/dataformat/ion/EnumAsIonSymbolSerializer.java

@@ -22,19 +22,20 @@
 import com.fasterxml.jackson.databind.JavaType;
 import com.fasterxml.jackson.databind.JsonMappingException;
 import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.SerializationFeature;
 import com.fasterxml.jackson.databind.SerializerProvider;
 import com.fasterxml.jackson.databind.jsonFormatVisitors.JsonFormatVisitorWrapper;
 import com.fasterxml.jackson.databind.ser.std.StdScalarSerializer;
 
 /**
  * Serializes enumeration members as IonSymbols.
- * 
+ *
  * Use annotation
- * 
+ *
  * <pre>
  * &#64;JsonSerialize(using=EnumAsIonSymbolSerializer.class)
  * </pre>
- * 
+ *
  * on enumeration members that should serialize at symbols (which amounts to serializing without being surrounded by
  * double-quotes)
  */
@@ -49,7 +50,11 @@ public EnumAsIonSymbolSerializer() {
     @Override
     public void serialize(Enum<?> value, JsonGenerator g, SerializerProvider provider) throws IOException {
         if (IonGenerator.class.isAssignableFrom(g.getClass())) {
-            ((IonGenerator) g).writeSymbol(value.name());
+            String valueString = provider.isEnabled(SerializationFeature.WRITE_ENUMS_USING_TO_STRING)
+                ? value.toString()
+                : value.name();
+
+            ((IonGenerator) g).writeSymbol(valueString);
         } else {
             throw new JsonGenerationException("Can only use EnumAsIonSymbolSerializer with IonGenerator", g);
         }

ion/src/test/java/com/fasterxml/jackson/dataformat/ion/EnumAsIonSymbolSerializationTest.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2014-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at:
+ *
+ *     http://aws.amazon.com/apache2.0/
+ *
+ * or in the "license" file accompanying this file. This file 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.
+ */
+
+package com.fasterxml.jackson.dataformat.ion;
+
+import java.io.IOException;
+import org.junit.Assert;
+import org.junit.Test;
+import com.amazon.ion.IonSystem;
+import com.amazon.ion.system.IonSystemBuilder;
+import com.fasterxml.jackson.databind.SerializationFeature;
+
+public class EnumAsIonSymbolSerializationTest {
+    private static final IonSystem ION_SYSTEM = IonSystemBuilder.standard().build();
+
+    @Test
+    public void testUsingName() throws IOException {
+        final IonObjectMapper mapper = newMapper();
+
+        Assert.assertEquals(
+            ION_SYSTEM.singleValue("SOME_VALUE"),
+            mapper.writeValueAsIonValue(SomeEnum.SOME_VALUE));
+    }
+
+    @Test
+    public void testUsingToString() throws IOException {
+        final IonObjectMapper mapper = newMapper();
+
+        mapper.enable(SerializationFeature.WRITE_ENUMS_USING_TO_STRING);
+
+        Assert.assertEquals(
+            ION_SYSTEM.singleValue("some_value"),
+            mapper.writeValueAsIonValue(SomeEnum.SOME_VALUE));
+    }
+
+    private static IonObjectMapper newMapper() {
+        final IonObjectMapper mapper = new IonObjectMapper(new IonFactory(null, ION_SYSTEM));
+        mapper.registerModule(new EnumAsIonSymbolModule());
+        return mapper;
+    }
+
+    private enum SomeEnum {
+        SOME_VALUE;
+
+        @Override
+        public String toString() {
+            return name().toLowerCase();
+        }
+    }
+}