Add extension superclass and exception

mopidy/exceptions.py

@@ -22,3 +22,7 @@ class SettingsError(MopidyException):
 
 class OptionalDependencyError(MopidyException):
     pass
+
+
+class ExtensionError(MopidyException):
+    pass

mopidy/ext.py

@@ -0,0 +1,27 @@
+from __future__ import unicode_literals
+
+
+class Extension(object):
+
+    name = None
+    version = None
+
+    def get_default_config(self):
+        raise NotImplementedError(
+            'Add at least a config section with "enabled = true"')
+
+    def validate_config(self, config):
+        raise NotImplementedError(
+            'You must explicitly pass config validation if not needed')
+
+    def validate_environment(self):
+        pass
+
+    def get_frontend_class(self):
+        pass
+
+    def get_backend_class(self):
+        pass
+
+    def register_gstreamer_elements(self):
+        pass

tests/exceptions_test.py

@@ -0,0 +1,25 @@
+from __future__ import unicode_literals
+
+from mopidy import exceptions
+
+from tests import unittest
+
+
+class ExceptionsTest(unittest.TestCase):
+    def test_exception_can_include_message_string(self):
+        exc = exceptions.MopidyException('foo')
+
+        self.assertEqual(exc.message, 'foo')
+        self.assertEqual(str(exc), 'foo')
+
+    def test_settings_error_is_a_mopidy_exception(self):
+        self.assert_(issubclass(
+            exceptions.SettingsError, exceptions.MopidyException))
+
+    def test_optional_dependency_error_is_a_mopidy_exception(self):
+        self.assert_(issubclass(
+            exceptions.OptionalDependencyError, exceptions.MopidyException))
+
+    def test_extension_error_is_a_mopidy_exception(self):
+        self.assert_(issubclass(
+            exceptions.ExtensionError, exceptions.MopidyException))

tests/ext_test.py

@@ -0,0 +1,34 @@
+from __future__ import unicode_literals
+
+from mopidy.ext import Extension
+
+from tests import unittest
+
+
+class ExtensionTest(unittest.TestCase):
+    def setUp(self):
+        self.ext = Extension()
+
+    def test_name_is_none(self):
+        self.assertIsNone(self.ext.name)
+
+    def test_version_is_none(self):
+        self.assertIsNone(self.ext.version)
+
+    def test_get_default_config_raises_not_implemented(self):
+        self.assertRaises(NotImplementedError, self.ext.get_default_config)
+
+    def test_validate_config_raises_not_implemented(self):
+        self.assertRaises(NotImplementedError, self.ext.validate_config, None)
+
+    def test_validate_environment_does_nothing_by_default(self):
+        self.assertIsNone(self.ext.validate_environment())
+
+    def test_get_frontend_class_returns_none_by_default(self):
+        self.assertIsNone(self.ext.get_frontend_class())
+
+    def test_get_backend_class_returns_none_by_default(self):
+        self.assertIsNone(self.ext.get_backend_class())
+
+    def test_register_gstreamer_elements_does_nothing_by_default(self):
+        self.assertIsNone(self.ext.register_gstreamer_elements())