config: Deserialize Secret to unicode (fix #473)

MPD, Scrobbler, and Spotify extensions have been reviewed for need for changes
due to this, without anything being found.

docs/changelog.rst

@@ -64,6 +64,11 @@ v0.15.0 (UNRELEASED)
   The methods are still not implemented, but now the commands are accepted as
   valid.
 
+**Extension support**
+
+- :class:`~mopidy.config.Secret` is now deserialized to unicode strings instead
+  of bytestrings. This may require modifications to extensions.
+
 
 v0.14.2 (2013-07-01)
 ====================

mopidy/config/types.py

@@ -82,30 +82,22 @@ class String(ConfigValue):
         return encode(value)
 
 
-class Secret(ConfigValue):
-    """Secret value.
+class Secret(String):
+    """Secret string value.
 
-    Should be used for passwords, auth tokens etc. Deserializing will not
-    convert to unicode. Will mask value when being displayed.
+    Is decoded as utf-8 and \\n \\t escapes should work and be preserved.
+
+    Should be used for passwords, auth tokens etc. Will mask value when being
+    displayed.
     """
     def __init__(self, optional=False, choices=None):
         self._required = not optional
-
-    def deserialize(self, value):
-        value = value.strip()
-        validators.validate_required(value, self._required)
-        if not value:
-            return None
-        return value
+        self._choices = None  # Choices doesn't make sense for secrets
 
     def serialize(self, value, display=False):
-        if isinstance(value, unicode):
-            value = value.encode('utf-8')
-        if value is None:
-            return b''
-        elif display:
+        if value is not None and display:
             return b'********'
-        return value
+        return super(Secret, self).serialize(value, display)
 
 
 class Integer(ConfigValue):

tests/config/types_test.py

@@ -105,11 +105,11 @@ class StringTest(unittest.TestCase):
 
 
 class SecretTest(unittest.TestCase):
-    def test_deserialize_passes_through(self):
+    def test_deserialize_decodes_utf8(self):
         value = types.Secret()
-        result = value.deserialize(b'foo')
-        self.assertIsInstance(result, bytes)
-        self.assertEqual(b'foo', result)
+        result = value.deserialize('æøå'.encode('utf-8'))
+        self.assertIsInstance(result, unicode)
+        self.assertEqual('æøå', result)
 
     def test_deserialize_enforces_required(self):
         value = types.Secret()