Check config before restarting (#5609)

* Check config before restarting.

* Make check_config on restart async

* don't check if notification service exists

* Use .communicate()

* Reduce the number of notifications. Add tests.

homeassistant/core.py

@@ -330,11 +330,40 @@ class HomeAssistant(object):
         self.exit_code = 0
         self.loop.create_task(self.async_stop())
 
+    @asyncio.coroutine
+    def _async_check_config_and_restart(self):
+        """Restart Home Assistant if config is valid.
+
+        This method is a coroutine.
+        """
+        proc = yield from asyncio.create_subprocess_exec(
+            sys.argv[0],
+            '--script',
+            'check_config',
+            stdout=asyncio.subprocess.PIPE)
+        # Wait for the subprocess exit
+        (stdout_data, dummy) = yield from proc.communicate()
+        result = yield from proc.wait()
+        if result:
+            _LOGGER.error("check_config failed. Not restarting.")
+            content = re.sub(r'\033\[[^m]*m', '', str(stdout_data, 'utf-8'))
+            # Put error cleaned from color codes in the error log so it
+            # will be visible at the UI.
+            _LOGGER.error(content)
+            yield from self.services.async_call(
+                'persistent_notification', 'create', {
+                    'message': 'Config error. See dev-info panel for details.',
+                    'title': 'Restarting',
+                    'notification_id': '{}.restart'.format(DOMAIN)})
+            return
+
+        self.exit_code = RESTART_EXIT_CODE
+        yield from self.async_stop()
+
     @callback
     def _async_restart_handler(self, *args):
         """Restart Home Assistant."""
-        self.exit_code = RESTART_EXIT_CODE
-        self.loop.create_task(self.async_stop())
+        self.loop.create_task(self._async_check_config_and_restart())
 
 
 class EventOrigin(enum.Enum):