Support maps in NanoPrinter.

javanano/src/main/java/com/google/protobuf/nano/MessageNanoPrinter.java

@@ -35,6 +35,7 @@ import java.lang.reflect.Field;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
+import java.util.Map;
 
 /**
  * Static helper methods for printing nano protos.
@@ -170,6 +171,19 @@ public final class MessageNanoPrinter {
                 indentBuf.setLength(origIndentBufLength);
                 buf.append(indentBuf).append(">\n");
             }
+        } else if (object instanceof Map) {
+          Map<?,?> map = (Map<?,?>) object;
+          identifier = deCamelCaseify(identifier);
+
+          for (Map.Entry<?,?> entry : map.entrySet()) {
+            buf.append(indentBuf).append(identifier).append(" <\n");
+            int origIndentBufLength = indentBuf.length();
+            indentBuf.append(INDENT);
+            print("key", entry.getKey(), indentBuf, buf);
+            print("value", entry.getValue(), indentBuf, buf);
+            indentBuf.setLength(origIndentBufLength);
+            buf.append(indentBuf).append(">\n");
+          }
         } else {
             // Non-null primitive value
             identifier = deCamelCaseify(identifier);

javanano/src/test/java/com/google/protobuf/nano/NanoTest.java

@@ -2731,6 +2731,45 @@ public class NanoTest extends TestCase {
     assertTrue(protoPrint.contains("id: 33"));
   }
 
+  public void testMessageNanoPrinterForMaps() throws Exception {
+    TestMap msg = new TestMap();
+    MessageValue msgValues[] = new MessageValue[] {
+      new MessageValue(), new MessageValue()
+    };
+    msgValues[0].value = 1;
+    msgValues[1].value = 2;
+    msg.int32ToBytesField = new HashMap<Integer, byte[]>();
+    msg.int32ToBytesField.put(1, new byte[] {'"', '\0'});
+    msg.int32ToBytesField.put(2, new byte[] {1, 8});
+    msg.stringToInt32Field = new HashMap<String, Integer>();
+    msg.stringToInt32Field.put("hello", 1);
+    msg.stringToInt32Field.put("world", 2);
+    msg.int32ToMessageField = new HashMap<Integer, MapTestProto.TestMap.MessageValue>();
+    msg.int32ToMessageField.put(0, msgValues[0]);
+    msg.int32ToMessageField.put(1, msgValues[1]);
+    msg.int32ToEnumField = new HashMap<Integer, Integer>();
+    msg.int32ToEnumField.put(1, 2);
+    msg.int32ToEnumField.put(2, 3);
+    String protoPrint = msg.toString();
+
+    assertTrue(protoPrint.contains(
+        "int32_to_bytes_field <\n  key: 1\n  value: \"\\\"\\000\"\n>"));
+    assertTrue(protoPrint.contains(
+        "int32_to_bytes_field <\n  key: 2\n  value: \"\\001\\010\"\n>"));
+    assertTrue(protoPrint.contains(
+        "string_to_int32_field <\n  key: \"hello\"\n  value: 1\n>"));
+    assertTrue(protoPrint.contains(
+        "string_to_int32_field <\n  key: \"world\"\n  value: 2\n>"));
+    assertTrue(protoPrint.contains(
+        "int32_to_message_field <\n  key: 0\n  value <\n    value: 1\n"));
+    assertTrue(protoPrint.contains(
+        "int32_to_message_field <\n  key: 1\n  value <\n    value: 2\n"));
+    assertTrue(protoPrint.contains(
+        "int32_to_enum_field <\n  key: 1\n  value: 2\n>"));
+    assertTrue(protoPrint.contains(
+        "int32_to_enum_field <\n  key: 2\n  value: 3\n>"));
+  }
+
   public void testExtensions() throws Exception {
     Extensions.ExtendableMessage message = new Extensions.ExtendableMessage();
     message.field = 5;