From e7a4f5fd2773c3cec0dbdb61325a60ed58131cc2 Mon Sep 17 00:00:00 2001
From: Claudio Ruggeri - CR-Tech <41435902+crug80@users.noreply.github.com>
Date: Thu, 23 Jan 2025 22:12:02 +0100
Subject: [PATCH] Fix slave id equal to 0 (#136263)

Co-authored-by: J. Nick Koston <nick@koston.org>
---
 homeassistant/components/modbus/entity.py |  5 ++-
 homeassistant/components/modbus/modbus.py |  4 +-
 tests/components/modbus/test_init.py      | 53 +++++++++++++++++++++++
 3 files changed, 60 insertions(+), 2 deletions(-)

diff --git a/homeassistant/components/modbus/entity.py b/homeassistant/components/modbus/entity.py
index 90833516e59..d252528f6d4 100644
--- a/homeassistant/components/modbus/entity.py
+++ b/homeassistant/components/modbus/entity.py
@@ -79,7 +79,10 @@ class BasePlatform(Entity):
         """Initialize the Modbus binary sensor."""
 
         self._hub = hub
-        self._slave = entry.get(CONF_SLAVE) or entry.get(CONF_DEVICE_ADDRESS, 0)
+        if (conf_slave := entry.get(CONF_SLAVE)) is not None:
+            self._slave = conf_slave
+        else:
+            self._slave = entry.get(CONF_DEVICE_ADDRESS, 1)
         self._address = int(entry[CONF_ADDRESS])
         self._input_type = entry[CONF_INPUT_TYPE]
         self._value: str | None = None
diff --git a/homeassistant/components/modbus/modbus.py b/homeassistant/components/modbus/modbus.py
index 8c8a879ead6..fce831e9cd4 100644
--- a/homeassistant/components/modbus/modbus.py
+++ b/homeassistant/components/modbus/modbus.py
@@ -368,7 +368,9 @@ class ModbusHub:
         self, slave: int | None, address: int, value: int | list[int], use_call: str
     ) -> ModbusPDU | None:
         """Call sync. pymodbus."""
-        kwargs = {"slave": slave} if slave else {}
+        kwargs: dict[str, Any] = (
+            {ATTR_SLAVE: slave} if slave is not None else {ATTR_SLAVE: 1}
+        )
         entry = self._pb_request[use_call]
         try:
             result: ModbusPDU = await entry.func(address, value, **kwargs)
diff --git a/tests/components/modbus/test_init.py b/tests/components/modbus/test_init.py
index 5dd3f6e9033..d37f55ede94 100644
--- a/tests/components/modbus/test_init.py
+++ b/tests/components/modbus/test_init.py
@@ -1265,3 +1265,56 @@ async def test_no_entities(hass: HomeAssistant) -> None:
         ]
     }
     assert await async_setup_component(hass, DOMAIN, config) is False
+
+
+@pytest.mark.parametrize(
+    ("do_config", "expected_slave_value"),
+    [
+        (
+            {
+                CONF_SENSORS: [
+                    {
+                        CONF_NAME: "dummy",
+                        CONF_ADDRESS: 1234,
+                    },
+                ],
+            },
+            1,
+        ),
+        (
+            {
+                CONF_SENSORS: [
+                    {
+                        CONF_NAME: "dummy",
+                        CONF_ADDRESS: 1234,
+                        CONF_SLAVE: 0,
+                    },
+                ],
+            },
+            0,
+        ),
+        (
+            {
+                CONF_SENSORS: [
+                    {
+                        CONF_NAME: "dummy",
+                        CONF_ADDRESS: 1234,
+                        CONF_DEVICE_ADDRESS: 6,
+                    },
+                ],
+            },
+            6,
+        ),
+    ],
+)
+async def test_check_default_slave(
+    hass: HomeAssistant,
+    mock_modbus,
+    do_config,
+    mock_do_cycle,
+    expected_slave_value: int,
+) -> None:
+    """Test default slave."""
+    assert mock_modbus.read_holding_registers.mock_calls
+    first_call = mock_modbus.read_holding_registers.mock_calls[0]
+    assert first_call.kwargs["slave"] == expected_slave_value