From d25f45a957327a94489f697c96b2425b2d5def55 Mon Sep 17 00:00:00 2001
From: jan iversen <jancasacondor@gmail.com>
Date: Sat, 16 Sep 2023 09:57:55 +0200
Subject: [PATCH] Harden modbus against lib errors (#100469)

---
 homeassistant/components/modbus/modbus.py | 6 ++++++
 tests/components/modbus/conftest.py       | 9 +++++++++
 tests/components/modbus/test_fan.py       | 5 ++++-
 tests/components/modbus/test_light.py     | 5 ++++-
 tests/components/modbus/test_switch.py    | 9 +++++++--
 5 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/homeassistant/components/modbus/modbus.py b/homeassistant/components/modbus/modbus.py
index a503b71593c..31179a23583 100644
--- a/homeassistant/components/modbus/modbus.py
+++ b/homeassistant/components/modbus/modbus.py
@@ -419,9 +419,15 @@ class ModbusHub:
         except ModbusException as exception_error:
             self._log_error(str(exception_error))
             return None
+        if not result:
+            self._log_error("Error: pymodbus returned None")
+            return None
         if not hasattr(result, entry.attr):
             self._log_error(str(result))
             return None
+        if result.isError():  # type: ignore[no-untyped-call]
+            self._log_error("Error: pymodbus returned isError True")
+            return None
         self._in_error = False
         return result
 
diff --git a/tests/components/modbus/conftest.py b/tests/components/modbus/conftest.py
index a08743b7e6c..460b1eb5dd3 100644
--- a/tests/components/modbus/conftest.py
+++ b/tests/components/modbus/conftest.py
@@ -32,6 +32,11 @@ class ReadResult:
         """Init."""
         self.registers = register_words
         self.bits = register_words
+        self.value = register_words
+
+    def isError(self):
+        """Set error state."""
+        return False
 
 
 @pytest.fixture(name="mock_pymodbus")
@@ -136,6 +141,10 @@ async def mock_pymodbus_return_fixture(hass, register_words, mock_modbus):
     mock_modbus.read_discrete_inputs.return_value = read_result
     mock_modbus.read_input_registers.return_value = read_result
     mock_modbus.read_holding_registers.return_value = read_result
+    mock_modbus.write_register.return_value = read_result
+    mock_modbus.write_registers.return_value = read_result
+    mock_modbus.write_coil.return_value = read_result
+    mock_modbus.write_coils.return_value = read_result
 
 
 @pytest.fixture(name="mock_do_cycle")
diff --git a/tests/components/modbus/test_fan.py b/tests/components/modbus/test_fan.py
index e47ed5c2371..932e07b2d1a 100644
--- a/tests/components/modbus/test_fan.py
+++ b/tests/components/modbus/test_fan.py
@@ -261,7 +261,10 @@ async def test_restore_state_fan(
     ],
 )
 async def test_fan_service_turn(
-    hass: HomeAssistant, caplog: pytest.LogCaptureFixture, mock_modbus
+    hass: HomeAssistant,
+    caplog: pytest.LogCaptureFixture,
+    mock_modbus,
+    mock_pymodbus_return,
 ) -> None:
     """Run test for service turn_on/turn_off."""
 
diff --git a/tests/components/modbus/test_light.py b/tests/components/modbus/test_light.py
index a5871bdbd67..1d6963aaa12 100644
--- a/tests/components/modbus/test_light.py
+++ b/tests/components/modbus/test_light.py
@@ -260,7 +260,10 @@ async def test_restore_state_light(
     ],
 )
 async def test_light_service_turn(
-    hass: HomeAssistant, caplog: pytest.LogCaptureFixture, mock_modbus
+    hass: HomeAssistant,
+    caplog: pytest.LogCaptureFixture,
+    mock_modbus,
+    mock_pymodbus_return,
 ) -> None:
     """Run test for service turn_on/turn_off."""
 
diff --git a/tests/components/modbus/test_switch.py b/tests/components/modbus/test_switch.py
index ff7d6860f3b..0eb40d2c082 100644
--- a/tests/components/modbus/test_switch.py
+++ b/tests/components/modbus/test_switch.py
@@ -316,7 +316,10 @@ async def test_restore_state_switch(
     ],
 )
 async def test_switch_service_turn(
-    hass: HomeAssistant, caplog: pytest.LogCaptureFixture, mock_modbus
+    hass: HomeAssistant,
+    caplog: pytest.LogCaptureFixture,
+    mock_modbus,
+    mock_pymodbus_return,
 ) -> None:
     """Run test for service turn_on/turn_off."""
     assert MODBUS_DOMAIN in hass.config.components
@@ -407,7 +410,9 @@ async def test_service_switch_update(hass: HomeAssistant, mock_modbus, mock_ha)
         },
     ],
 )
-async def test_delay_switch(hass: HomeAssistant, mock_modbus) -> None:
+async def test_delay_switch(
+    hass: HomeAssistant, mock_modbus, mock_pymodbus_return
+) -> None:
     """Run test for switch verify delay."""
     mock_modbus.read_holding_registers.return_value = ReadResult([0x01])
     now = dt_util.utcnow()