Fix modbus default delay (#33877)

* solve modbus issue #33872

CONF_DELAY was used in a serial connection, which is not
permitted.

Sometimes async_update is called after async_setup is completed,
but before event EVENT_HOMEASSISTANT_START is issued, leading to
a missing object.

* resolve review comment.

Do not wait for start event, but activate pymodbus directly in
async setup.

* review 2

Remark, this does not work, async_setup hangs.

clean start_modbus() from async calls, leaving only the pymodbus
setup.

* review 2a

Moved listen_once back to start_modbus, since it is sync.

homeassistant/components/modbus/__init__.py

@@ -21,7 +21,6 @@ from homeassistant.const import (
     CONF_PORT,
     CONF_TIMEOUT,
     CONF_TYPE,
-    EVENT_HOMEASSISTANT_START,
     EVENT_HOMEASSISTANT_STOP,
 )
 import homeassistant.helpers.config_validation as cv
@@ -106,27 +105,13 @@ async def async_setup(hass, config):
         for client in hub_collect.values():
             del client
 
-    def start_modbus(event):
+    def start_modbus():
         """Start Modbus service."""
         for client in hub_collect.values():
             client.setup()
 
         hass.bus.listen_once(EVENT_HOMEASSISTANT_STOP, stop_modbus)
 
-        # Register services for modbus
-        hass.services.async_register(
-            MODBUS_DOMAIN,
-            SERVICE_WRITE_REGISTER,
-            write_register,
-            schema=SERVICE_WRITE_REGISTER_SCHEMA,
-        )
-        hass.services.async_register(
-            MODBUS_DOMAIN,
-            SERVICE_WRITE_COIL,
-            write_coil,
-            schema=SERVICE_WRITE_COIL_SCHEMA,
-        )
-
     async def write_register(service):
         """Write Modbus registers."""
         unit = int(float(service.data[ATTR_UNIT]))
@@ -150,8 +135,19 @@ async def async_setup(hass, config):
         client_name = service.data[ATTR_HUB]
         await hub_collect[client_name].write_coil(unit, address, state)
 
-    hass.bus.async_listen_once(EVENT_HOMEASSISTANT_START, start_modbus)
+    # do not wait for EVENT_HOMEASSISTANT_START, activate pymodbus now
+    await hass.async_add_executor_job(start_modbus)
 
+    # Register services for modbus
+    hass.services.async_register(
+        MODBUS_DOMAIN,
+        SERVICE_WRITE_REGISTER,
+        write_register,
+        schema=SERVICE_WRITE_REGISTER_SCHEMA,
+    )
+    hass.services.async_register(
+        MODBUS_DOMAIN, SERVICE_WRITE_COIL, write_coil, schema=SERVICE_WRITE_COIL_SCHEMA,
+    )
     return True
 
 
@@ -169,7 +165,7 @@ class ModbusHub:
         self._config_type = client_config[CONF_TYPE]
         self._config_port = client_config[CONF_PORT]
         self._config_timeout = client_config[CONF_TIMEOUT]
-        self._config_delay = client_config[CONF_DELAY]
+        self._config_delay = 0
 
         if self._config_type == "serial":
             # serial configuration
@@ -181,6 +177,7 @@ class ModbusHub:
         else:
             # network configuration
             self._config_host = client_config[CONF_HOST]
+            self._config_delay = client_config[CONF_DELAY]
 
     @property
     def name(self):