Add support for locks in google assistant component (#18233)

* Add support for locks in google assistant component

This is supported by the smarthome API, but there is no documentation
for it. This work is based on an article I found with screenshots of
documentation that was erroneously uploaded:

https://www.androidpolice.com/2018/01/17/google-assistant-home-can-now-natively-control-smart-locks-august-vivint-first-supported/

Google Assistant now supports unlocking certain locks - Nest and August
come to mind - via this API, and this commit allows Home Assistant to
do so as well.

Notably, I've added a config option `allow_unlock` that controls
whether we actually honor requests to unlock a lock via the google
assistant. It defaults to false.

Additionally, we add the functionNotSupported error, which makes a
little more sense when we're unable to execute the desired state
transition.

https://developers.google.com/actions/reference/smarthome/errors-exceptions#exception_list

* Fix linter warnings

* Ensure that certain groups are never exposed to cloud entities

For example, the group.all_locks entity - we should probably never
expose this to third party cloud integrations. It's risky.

This is not configurable, but can be extended by adding to the
cloud.const.NEVER_EXPOSED_ENTITIES array.

It's implemented in a modestly hacky fashion, because we determine
whether or not a entity should be excluded/included in several ways.

Notably, we define this array in the top level const.py, to avoid
circular import problems between the cloud/alexa components.

homeassistant/components/google_assistant/trait.py

@@ -10,6 +10,7 @@ from homeassistant.components import (
     input_boolean,
     media_player,
     light,
+    lock,
     scene,
     script,
     switch,
@@ -19,6 +20,7 @@ from homeassistant.const import (
     ATTR_ENTITY_ID,
     SERVICE_TURN_OFF,
     SERVICE_TURN_ON,
+    STATE_LOCKED,
     STATE_OFF,
     TEMP_CELSIUS,
     TEMP_FAHRENHEIT,
@@ -40,6 +42,7 @@ TRAIT_COLOR_SPECTRUM = PREFIX_TRAITS + 'ColorSpectrum'
 TRAIT_COLOR_TEMP = PREFIX_TRAITS + 'ColorTemperature'
 TRAIT_SCENE = PREFIX_TRAITS + 'Scene'
 TRAIT_TEMPERATURE_SETTING = PREFIX_TRAITS + 'TemperatureSetting'
+TRAIT_LOCKUNLOCK = PREFIX_TRAITS + 'LockUnlock'
 
 PREFIX_COMMANDS = 'action.devices.commands.'
 COMMAND_ONOFF = PREFIX_COMMANDS + 'OnOff'
@@ -54,6 +57,7 @@ COMMAND_THERMOSTAT_TEMPERATURE_SETPOINT = (
 COMMAND_THERMOSTAT_TEMPERATURE_SET_RANGE = (
     PREFIX_COMMANDS + 'ThermostatTemperatureSetRange')
 COMMAND_THERMOSTAT_SET_MODE = PREFIX_COMMANDS + 'ThermostatSetMode'
+COMMAND_LOCKUNLOCK = PREFIX_COMMANDS + 'LockUnlock'
 
 
 TRAITS = []
@@ -77,10 +81,11 @@ class _Trait:
 
     commands = []
 
-    def __init__(self, hass, state):
+    def __init__(self, hass, state, config):
         """Initialize a trait for a state."""
         self.hass = hass
         self.state = state
+        self.config = config
 
     def sync_attributes(self):
         """Return attributes for a sync request."""
@@ -628,3 +633,45 @@ class TemperatureSettingTrait(_Trait):
                     climate.ATTR_OPERATION_MODE:
                         self.google_to_hass[params['thermostatMode']],
                 }, blocking=True)
+
+
+@register_trait
+class LockUnlockTrait(_Trait):
+    """Trait to lock or unlock a lock.
+
+    https://developers.google.com/actions/smarthome/traits/lockunlock
+    """
+
+    name = TRAIT_LOCKUNLOCK
+    commands = [
+        COMMAND_LOCKUNLOCK
+    ]
+
+    @staticmethod
+    def supported(domain, features):
+        """Test if state is supported."""
+        return domain == lock.DOMAIN
+
+    def sync_attributes(self):
+        """Return LockUnlock attributes for a sync request."""
+        return {}
+
+    def query_attributes(self):
+        """Return LockUnlock query attributes."""
+        return {'isLocked': self.state.state == STATE_LOCKED}
+
+    def can_execute(self, command, params):
+        """Test if command can be executed."""
+        allowed_unlock = not params['lock'] and self.config.allow_unlock
+        return params['lock'] or allowed_unlock
+
+    async def execute(self, command, params):
+        """Execute an LockUnlock command."""
+        if params['lock']:
+            service = lock.SERVICE_LOCK
+        else:
+            service = lock.SERVICE_UNLOCK
+
+        await self.hass.services.async_call(lock.DOMAIN, service, {
+            ATTR_ENTITY_ID: self.state.entity_id
+        }, blocking=True)