Accept group without entities in configuration. (#1768)

* Accept group without entities in configuration.

People seem to use these as placeholders for future expansion of their
home automation dreams, and we used to accept them.  We still have to
specify at least one of 'name', 'view' or 'icon' so that the group is
parsed as a dictionary.

* Also accept empty entities: key in a group.

* Additional fix for empty entities value in a group config.

homeassistant/components/group.py

@@ -39,7 +39,7 @@ def _conf_preprocess(value):
     return value
 
 _SINGLE_GROUP_CONFIG = vol.Schema(vol.All(_conf_preprocess, {
-    vol.Required(CONF_ENTITIES): cv.entity_ids,
+    vol.Optional(CONF_ENTITIES): vol.Any(None, cv.entity_ids),
     CONF_VIEW: bool,
     CONF_NAME: str,
     CONF_ICON: cv.icon,
@@ -145,7 +145,7 @@ def setup(hass, config):
     """Setup all groups found definded in the configuration."""
     for object_id, conf in config.get(DOMAIN, {}).items():
         name = conf.get(CONF_NAME, object_id)
-        entity_ids = conf[CONF_ENTITIES]
+        entity_ids = conf.get(CONF_ENTITIES) or []
         icon = conf.get(CONF_ICON)
         view = conf.get(CONF_VIEW)
 

tests/components/test_group.py

@@ -226,6 +226,7 @@ class TestComponentsGroup(unittest.TestCase):
                         'view': True,
                     },
                     'test_group': 'hello.world,sensor.happy',
+                    'empty_group': {'name': 'Empty Group', 'entities': None},
                 }
             })