Fix write_registers calling after the upgrade of pymodbus to 3.8.x

homeassistant/components/modbus/modbus.py

@@ -384,6 +384,11 @@ async def low_level_pb_call(
             {ATTR_SLAVE: slave} if slave is not None else {ATTR_SLAVE: 1}
         )
         entry = self._pb_request[use_call]
+
+        if use_call in {"write_registers", "write_coils"}:
+            if not isinstance(value, list):
+                value = [value]
+
         kwargs[entry.value_attr_name] = value
         try:
             result: ModbusPDU = await entry.func(address, **kwargs)

tests/components/modbus/conftest.py

@@ -42,6 +42,7 @@ def __init__(self, register_words) -> None:
         self.registers = register_words
         self.bits = register_words
         self.value = register_words
+        self.count = len(register_words) if register_words is not None else 0
 
     def isError(self):
         """Set error state."""

tests/components/modbus/test_switch.py

@@ -12,6 +12,7 @@
     CALL_TYPE_DISCRETE,
     CALL_TYPE_REGISTER_HOLDING,
     CALL_TYPE_REGISTER_INPUT,
+    CALL_TYPE_X_REGISTER_HOLDINGS,
     CONF_DEVICE_ADDRESS,
     CONF_INPUT_TYPE,
     CONF_STATE_OFF,
@@ -50,6 +51,7 @@
 ENTITY_ID = f"{SWITCH_DOMAIN}.{TEST_ENTITY_NAME}".replace(" ", "_")
 ENTITY_ID2 = f"{ENTITY_ID}_2"
 ENTITY_ID3 = f"{ENTITY_ID}_3"
+ENTITY_ID4 = f"{ENTITY_ID}_4"
 
 
 @pytest.mark.parametrize(
@@ -330,6 +332,13 @@ async def test_restore_state_switch(
                     CONF_SCAN_INTERVAL: 0,
                     CONF_VERIFY: {CONF_STATE_ON: [1, 3]},
                 },
+                {
+                    CONF_NAME: f"{TEST_ENTITY_NAME} 4",
+                    CONF_ADDRESS: 19,
+                    CONF_WRITE_TYPE: CALL_TYPE_X_REGISTER_HOLDINGS,
+                    CONF_SCAN_INTERVAL: 0,
+                    CONF_VERIFY: {CONF_STATE_ON: [1, 3]},
+                },
             ],
         },
     ],
@@ -381,6 +390,20 @@ async def test_switch_service_turn(
     await hass.async_block_till_done()
     assert hass.states.get(ENTITY_ID3).state == STATE_OFF
 
+    mock_modbus.read_holding_registers.return_value = ReadResult([0x03])
+    assert hass.states.get(ENTITY_ID4).state == STATE_OFF
+    await hass.services.async_call(
+        SWITCH_DOMAIN, SERVICE_TURN_ON, service_data={ATTR_ENTITY_ID: ENTITY_ID4}
+    )
+    await hass.async_block_till_done()
+    assert hass.states.get(ENTITY_ID4).state == STATE_ON
+    mock_modbus.read_holding_registers.return_value = ReadResult([0x00])
+    await hass.services.async_call(
+        SWITCH_DOMAIN, SERVICE_TURN_OFF, service_data={ATTR_ENTITY_ID: ENTITY_ID4}
+    )
+    await hass.async_block_till_done()
+    assert hass.states.get(ENTITY_ID4).state == STATE_OFF
+
     mock_modbus.write_register.side_effect = ModbusException("fail write_")
     await hass.services.async_call(
         SWITCH_DOMAIN, SERVICE_TURN_ON, service_data={ATTR_ENTITY_ID: ENTITY_ID2}