Add optimistic mode to template switch

homeassistant/components/template/switch.py

@@ -24,6 +24,7 @@
 import homeassistant.helpers.config_validation as cv
 from homeassistant.helpers.entity import async_generate_entity_id
 from homeassistant.helpers.event import async_track_state_change
+from homeassistant.helpers.restore_state import RestoreEntity
 from homeassistant.helpers.script import Script
 
 from . import extract_entities, initialise_templates
@@ -37,7 +38,7 @@
 
 SWITCH_SCHEMA = vol.Schema(
     {
-        vol.Required(CONF_VALUE_TEMPLATE): cv.template,
+        vol.Optional(CONF_VALUE_TEMPLATE): cv.template,
         vol.Optional(CONF_ICON_TEMPLATE): cv.template,
         vol.Optional(CONF_ENTITY_PICTURE_TEMPLATE): cv.template,
         vol.Optional(CONF_AVAILABILITY_TEMPLATE): cv.template,
@@ -59,7 +60,7 @@ async def async_setup_platform(hass, config, async_add_entities, discovery_info=
 
     for device, device_config in config[CONF_SWITCHES].items():
         friendly_name = device_config.get(ATTR_FRIENDLY_NAME, device)
-        state_template = device_config[CONF_VALUE_TEMPLATE]
+        state_template = device_config.get(CONF_VALUE_TEMPLATE)
         icon_template = device_config.get(CONF_ICON_TEMPLATE)
         entity_picture_template = device_config.get(CONF_ENTITY_PICTURE_TEMPLATE)
         availability_template = device_config.get(CONF_AVAILABILITY_TEMPLATE)
@@ -96,7 +97,7 @@ async def async_setup_platform(hass, config, async_add_entities, discovery_info=
     async_add_entities(switches)
 
 
-class SwitchTemplate(SwitchEntity):
+class SwitchTemplate(SwitchEntity, RestoreEntity):
     """Representation of a Template switch."""
 
     def __init__(
@@ -133,6 +134,18 @@ def __init__(
     async def async_added_to_hass(self):
         """Register callbacks."""
 
+        if self._template is None:
+
+            # restore state after startup
+            await super().async_added_to_hass()
+            state = await self.async_get_last_state()
+            if state:
+                self._state = state.state == STATE_ON
+
+            # no need to listen for events
+            return
+
+        # set up event listening
         @callback
         def template_switch_state_listener(entity, old_state, new_state):
             """Handle target device state changes."""
@@ -184,13 +197,21 @@ def available(self) -> bool:
     async def async_turn_on(self, **kwargs):
         """Fire the on action."""
         await self._on_script.async_run(context=self._context)
+        if self._template is None:
+            self._state = True
+            self.async_write_ha_state()
 
     async def async_turn_off(self, **kwargs):
         """Fire the off action."""
         await self._off_script.async_run(context=self._context)
+        if self._template is None:
+            self._state = False
+            self.async_write_ha_state()
 
     async def async_update(self):
         """Update the state from the template."""
+        if self._template is None:
+            return
         try:
             state = self._template.async_render().lower()
 
@@ -243,3 +264,8 @@ async def async_update(self):
                         self._name,
                         ex,
                     )
+
+    @property
+    def assumed_state(self):
+        """State is assumed, if no template given."""
+        return self._template is None