From 5193e3115d8a9dabef3b7b6cd423b8df5eaaca1b Mon Sep 17 00:00:00 2001
From: Marvin Wichmann <marvin.wichmann@unic.com>
Date: Fri, 22 Oct 2021 20:52:41 +0200
Subject: [PATCH] Restore the previous state of a KNX binary sensor (#57891)

---
 homeassistant/components/knx/binary_sensor.py | 19 ++++-
 tests/components/knx/test_binary_sensor.py    | 69 ++++++++++++++++++-
 2 files changed, 85 insertions(+), 3 deletions(-)

diff --git a/homeassistant/components/knx/binary_sensor.py b/homeassistant/components/knx/binary_sensor.py
index 9a9c9627670..7a3de7e1ec0 100644
--- a/homeassistant/components/knx/binary_sensor.py
+++ b/homeassistant/components/knx/binary_sensor.py
@@ -7,9 +7,16 @@ from xknx import XKNX
 from xknx.devices import BinarySensor as XknxBinarySensor
 
 from homeassistant.components.binary_sensor import BinarySensorEntity
-from homeassistant.const import CONF_DEVICE_CLASS, CONF_NAME
+from homeassistant.const import (
+    CONF_DEVICE_CLASS,
+    CONF_NAME,
+    STATE_ON,
+    STATE_UNAVAILABLE,
+    STATE_UNKNOWN,
+)
 from homeassistant.core import HomeAssistant
 from homeassistant.helpers.entity_platform import AddEntitiesCallback
+from homeassistant.helpers.restore_state import RestoreEntity
 from homeassistant.helpers.typing import ConfigType, DiscoveryInfoType
 from homeassistant.util import dt
 
@@ -36,7 +43,7 @@ async def async_setup_platform(
     )
 
 
-class KNXBinarySensor(KnxEntity, BinarySensorEntity):
+class KNXBinarySensor(KnxEntity, BinarySensorEntity, RestoreEntity):
     """Representation of a KNX binary sensor."""
 
     _device: XknxBinarySensor
@@ -61,6 +68,14 @@ class KNXBinarySensor(KnxEntity, BinarySensorEntity):
         self._attr_force_update = self._device.ignore_internal_state
         self._attr_unique_id = str(self._device.remote_value.group_address_state)
 
+    async def async_added_to_hass(self) -> None:
+        """Restore last state."""
+        await super().async_added_to_hass()
+        if (
+            last_state := await self.async_get_last_state()
+        ) and last_state.state not in (STATE_UNKNOWN, STATE_UNAVAILABLE):
+            await self._device.remote_value.update_value(last_state.state == STATE_ON)
+
     @property
     def is_on(self) -> bool:
         """Return true if the binary sensor is on."""
diff --git a/tests/components/knx/test_binary_sensor.py b/tests/components/knx/test_binary_sensor.py
index 1cb9f14e61f..811c8ab1341 100644
--- a/tests/components/knx/test_binary_sensor.py
+++ b/tests/components/knx/test_binary_sensor.py
@@ -1,10 +1,11 @@
 """Test KNX binary sensor."""
 from datetime import timedelta
+from unittest.mock import patch
 
 from homeassistant.components.knx.const import CONF_STATE_ADDRESS, CONF_SYNC_STATE
 from homeassistant.components.knx.schema import BinarySensorSchema
 from homeassistant.const import CONF_NAME, STATE_OFF, STATE_ON
-from homeassistant.core import HomeAssistant
+from homeassistant.core import HomeAssistant, State
 from homeassistant.util import dt
 
 from .conftest import KNXTestKit
@@ -213,3 +214,69 @@ async def test_binary_sensor_reset(hass: HomeAssistant, knx: KNXTestKit):
     # state reset after after timeout
     state = hass.states.get("binary_sensor.test")
     assert state.state is STATE_OFF
+
+
+async def test_binary_sensor_restore_and_respond(hass, knx):
+    """Test restoring KNX binary sensor state and respond to read."""
+    _ADDRESS = "2/2/2"
+    fake_state = State("binary_sensor.test", STATE_ON)
+
+    with patch(
+        "homeassistant.helpers.restore_state.RestoreEntity.async_get_last_state",
+        return_value=fake_state,
+    ):
+        await knx.setup_integration(
+            {
+                BinarySensorSchema.PLATFORM_NAME: [
+                    {
+                        CONF_NAME: "test",
+                        CONF_STATE_ADDRESS: _ADDRESS,
+                        CONF_SYNC_STATE: False,
+                    },
+                ]
+            }
+        )
+
+    # restored state - doesn't send telegram
+    state = hass.states.get("binary_sensor.test")
+    assert state.state == STATE_ON
+    await knx.assert_telegram_count(0)
+
+    await knx.receive_write(_ADDRESS, False)
+    await hass.async_block_till_done()
+    state = hass.states.get("binary_sensor.test")
+    assert state.state is STATE_OFF
+
+
+async def test_binary_sensor_restore_invert(hass, knx):
+    """Test restoring KNX binary sensor state with invert."""
+    _ADDRESS = "2/2/2"
+    fake_state = State("binary_sensor.test", STATE_ON)
+
+    with patch(
+        "homeassistant.helpers.restore_state.RestoreEntity.async_get_last_state",
+        return_value=fake_state,
+    ):
+        await knx.setup_integration(
+            {
+                BinarySensorSchema.PLATFORM_NAME: [
+                    {
+                        CONF_NAME: "test",
+                        CONF_STATE_ADDRESS: _ADDRESS,
+                        BinarySensorSchema.CONF_INVERT: True,
+                        CONF_SYNC_STATE: False,
+                    },
+                ]
+            }
+        )
+
+    # restored state - doesn't send telegram
+    state = hass.states.get("binary_sensor.test")
+    assert state.state == STATE_ON
+    await knx.assert_telegram_count(0)
+
+    # inverted is on, make sure the state is off after it
+    await knx.receive_write(_ADDRESS, True)
+    await hass.async_block_till_done()
+    state = hass.states.get("binary_sensor.test")
+    assert state.state is STATE_OFF