Add recent context (#15989)

* Add recent context

* Add async_set_context to components not using new services

homeassistant/helpers/entity.py

@@ -1,5 +1,6 @@
 """An abstract class for entities."""
 import asyncio
+from datetime import timedelta
 import logging
 import functools as ft
 from timeit import default_timer as timer
@@ -16,6 +17,7 @@ from homeassistant.config import DATA_CUSTOMIZE
 from homeassistant.exceptions import NoEntitySpecifiedError
 from homeassistant.util import ensure_unique_string, slugify
 from homeassistant.util.async_ import run_callback_threadsafe
+from homeassistant.util import dt as dt_util
 
 _LOGGER = logging.getLogger(__name__)
 SLOW_UPDATE_WARNING = 10
@@ -85,6 +87,10 @@ class Entity:
     # Hold list for functions to call on remove.
     _on_remove = None
 
+    # Context
+    _context = None
+    _context_set = None
+
     @property
     def should_poll(self) -> bool:
         """Return True if entity has to be polled for state.
@@ -173,13 +179,24 @@ class Entity:
         """Flag supported features."""
         return None
 
+    @property
+    def context_recent_time(self):
+        """Time that a context is considered recent."""
+        return timedelta(seconds=5)
+
     # DO NOT OVERWRITE
     # These properties and methods are either managed by Home Assistant or they
     # are used to perform a very specific function. Overwriting these may
     # produce undesirable effects in the entity's operation.
 
+    @callback
+    def async_set_context(self, context):
+        """Set the context the entity currently operates under."""
+        self._context = context
+        self._context_set = dt_util.utcnow()
+
     @asyncio.coroutine
-    def async_update_ha_state(self, force_refresh=False, context=None):
+    def async_update_ha_state(self, force_refresh=False):
         """Update Home Assistant with current state of entity.
 
         If force_refresh == True will update entity before setting state.
@@ -278,8 +295,14 @@ class Entity:
             # Could not convert state to float
             pass
 
+        if (self._context is not None and
+                dt_util.utcnow() - self._context_set >
+                self.context_recent_time):
+            self._context = None
+            self._context_set = None
+
         self.hass.states.async_set(
-            self.entity_id, state, attr, self.force_update, context)
+            self.entity_id, state, attr, self.force_update, self._context)
 
     def schedule_update_ha_state(self, force_refresh=False):
         """Schedule an update ha state change task.