Fixes an issue where Chromecast audio groups were not properly discovered (#3630)

* Fixes an issue where Chromecast audio groups were not properly discovered

* Forgot to commit the main fix

* Removes unused variable

* Doesn't use a protected API anymore

* PR remarks

* Fixes tests, adds comment

* Restores line as it was in the original commit, rephrases comment

* Should fix lint issues

* Trailing whitespace

* Some more lint

homeassistant/components/media_player/cast.py

@@ -68,12 +68,19 @@ def setup_platform(hass, config, add_devices, discovery_info=None):
 
     casts = []
 
+    # get_chromecasts() returns Chromecast objects
+    # with the correct friendly name for grouped devices
+    all_chromecasts = pychromecast.get_chromecasts()
+
     for host in hosts:
-        try:
-            casts.append(CastDevice(*host))
-            KNOWN_HOSTS.append(host)
-        except pychromecast.ChromecastConnectionError:
-            pass
+        found = [device for device in all_chromecasts
+                 if (device.host, device.port) == host]
+        if found:
+            try:
+                casts.append(CastDevice(found[0]))
+                KNOWN_HOSTS.append(host)
+            except pychromecast.ChromecastConnectionError:
+                pass
 
     add_devices(casts)
 
@@ -83,10 +90,9 @@ class CastDevice(MediaPlayerDevice):
 
     # pylint: disable=abstract-method
     # pylint: disable=too-many-public-methods
-    def __init__(self, host, port):
+    def __init__(self, chromecast):
         """Initialize the Cast device."""
-        import pychromecast
-        self.cast = pychromecast.Chromecast(host, port)
+        self.cast = chromecast
 
         self.cast.socket_client.receiver_controller.register_status_listener(
             self)

tests/components/media_player/test_cast.py

@@ -6,12 +6,25 @@ from unittest.mock import patch
 from homeassistant.components.media_player import cast
 
 
+class FakeChromeCast(object):
+    def __init__(self, host, port):
+        self.host = host
+        self.port = port
+
+
 class TestCastMediaPlayer(unittest.TestCase):
     """Test the media_player module."""
 
     @patch('homeassistant.components.media_player.cast.CastDevice')
-    def test_filter_duplicates(self, mock_device):
+    @patch('pychromecast.get_chromecasts')
+    def test_filter_duplicates(self, mock_get_chromecasts, mock_device):
         """Test filtering of duplicates."""
+
+        mock_get_chromecasts.return_value = [
+            FakeChromeCast('some_host', cast.DEFAULT_PORT)
+        ]
+
+        # Test chromecasts as if they were hardcoded in configuration.yaml
         cast.setup_platform(None, {
             'host': 'some_host'
         }, lambda _: _)
@@ -21,6 +34,7 @@ class TestCastMediaPlayer(unittest.TestCase):
         mock_device.reset_mock()
         assert not mock_device.called
 
+        # Test chromecasts as if they were automatically discovered
         cast.setup_platform(None, {}, lambda _: _, ('some_host',
                                                     cast.DEFAULT_PORT))
         assert not mock_device.called