ext: Support multiple frontends/backends in an extension

docs/extensiondev.rst

@@ -265,13 +265,13 @@ meaningful defaults blank, like ``username`` and ``password``.
         # You will typically only implement one of the next three methods
         # in a single extension.
 
-        def get_frontend_class(self):
+        def get_frontend_classes(self):
             from .frontend import SoundspotFrontend
-            return SoundspotFrontend
+            return [SoundspotFrontend]
 
-        def get_backend_class(self):
+        def get_backend_classes(self):
             from .backend import SoundspotBackend
-            return SoundspotBackend
+            return [SoundspotBackend]
 
         def register_gstreamer_elements(self):
             from .mixer import SoundspotMixer

mopidy/ext.py

@@ -17,11 +17,11 @@ class Extension(object):
     def validate_environment(self):
         pass
 
-    def get_frontend_class(self):
-        pass
+    def get_frontend_classes(self):
+        return []
 
-    def get_backend_class(self):
-        pass
+    def get_backend_classes(self):
+        return []
 
     def register_gstreamer_elements(self):
         pass

tests/ext_test.py

@@ -24,11 +24,11 @@ class ExtensionTest(unittest.TestCase):
     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_frontend_classes_returns_an_empty_list(self):
+        self.assertListEqual(self.ext.get_frontend_classes(), [])
 
-    def test_get_backend_class_returns_none_by_default(self):
-        self.assertIsNone(self.ext.get_backend_class())
+    def test_get_backend_classes_returns_an_empty_list(self):
+        self.assertListEqual(self.ext.get_backend_classes(), [])
 
     def test_register_gstreamer_elements_does_nothing_by_default(self):
         self.assertIsNone(self.ext.register_gstreamer_elements())