From 0d74be0b1e676b350f836270a3b309afa5c2133e Mon Sep 17 00:00:00 2001
From: kingosticks <kingosticks@gmail.com>
Date: Mon, 6 Jan 2014 11:54:28 +0000
Subject: [PATCH] Empty MPD commands should return an error instead of OK, just
 like the original MPD server. Includes tests.

---
 docs/changelog.rst                    |  5 +++++
 mopidy/mpd/exceptions.py              |  6 ++++++
 mopidy/mpd/protocol/empty.py          |  5 +++--
 tests/mpd/exception_test.py           | 10 +++++++++-
 tests/mpd/protocol/connection_test.py |  4 ++--
 5 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/docs/changelog.rst b/docs/changelog.rst
index b0e9fa45..e3b4826f 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -7,6 +7,11 @@ This changelog is used to track all major changes to Mopidy.
 v0.18.0 (UNRELEASED)
 ====================
 
+**MPD frontend**
+
+- Empty commands now return a ``ACK [5@0] {} No command given`` error instead
+  of ``OK``. This is consistent with the original MPD server implementation.
+
 **Core API**
 
 - Expose :meth:`mopidy.core.Core.version` for HTTP clients to manage
diff --git a/mopidy/mpd/exceptions.py b/mopidy/mpd/exceptions.py
index db3212d8..07e3a421 100644
--- a/mopidy/mpd/exceptions.py
+++ b/mopidy/mpd/exceptions.py
@@ -62,6 +62,12 @@ class MpdUnknownCommand(MpdAckError):
         self.command = ''
 
 
+class MpdNoCommand(MpdUnknownCommand):
+    def __init__(self, *args, **kwargs):
+        super(MpdNoCommand, self).__init__(*args, **kwargs)
+        self.message = 'No command given'
+
+
 class MpdNoExistError(MpdAckError):
     error_code = MpdAckError.ACK_ERROR_NO_EXIST
 
diff --git a/mopidy/mpd/protocol/empty.py b/mopidy/mpd/protocol/empty.py
index 9b3d6883..9cb0aa6b 100644
--- a/mopidy/mpd/protocol/empty.py
+++ b/mopidy/mpd/protocol/empty.py
@@ -1,9 +1,10 @@
 from __future__ import unicode_literals
 
 from mopidy.mpd.protocol import handle_request
+from mopidy.mpd.exceptions import MpdNoCommand
 
 
 @handle_request(r'[\ ]*$')
 def empty(context):
-    """The original MPD server returns ``OK`` on an empty request."""
-    pass
+    """The original MPD server returns an error on an empty request."""
+    raise MpdNoCommand
diff --git a/tests/mpd/exception_test.py b/tests/mpd/exception_test.py
index ae59253e..df815cfa 100644
--- a/tests/mpd/exception_test.py
+++ b/tests/mpd/exception_test.py
@@ -3,7 +3,7 @@ from __future__ import unicode_literals
 import unittest
 
 from mopidy.mpd.exceptions import (
-    MpdAckError, MpdPermissionError, MpdUnknownCommand, MpdSystemError,
+    MpdAckError, MpdPermissionError, MpdUnknownCommand, MpdNoCommand, MpdSystemError,
     MpdNotImplemented)
 
 
@@ -41,6 +41,14 @@ class MpdExceptionsTest(unittest.TestCase):
                 e.get_mpd_ack(),
                 'ACK [5@0] {} unknown command "play"')
 
+    def test_mpd_no_command(self):
+        try:
+            raise MpdNoCommand
+        except MpdAckError as e:
+            self.assertEqual(
+                e.get_mpd_ack(),
+                'ACK [5@0] {} No command given')
+
     def test_mpd_system_error(self):
         try:
             raise MpdSystemError('foo')
diff --git a/tests/mpd/protocol/connection_test.py b/tests/mpd/protocol/connection_test.py
index 452a2147..34cce6a0 100644
--- a/tests/mpd/protocol/connection_test.py
+++ b/tests/mpd/protocol/connection_test.py
@@ -14,10 +14,10 @@ class ConnectionHandlerTest(protocol.BaseTestCase):
 
     def test_empty_request(self):
         self.sendRequest('')
-        self.assertEqualResponse('OK')
+        self.assertEqualResponse('ACK [5@0] {} No command given')
 
         self.sendRequest('  ')
-        self.assertEqualResponse('OK')
+        self.assertEqualResponse('ACK [5@0] {} No command given')
 
     def test_kill(self):
         self.sendRequest('kill')