Allow removing devices that are no longer on the gateway

README.md

@@ -136,3 +136,15 @@ _The DPWS service configuration_
  2. Depending on where you added your PowerTags, press _ADD DEVICE_ or _ADD_SOLAR_PRODUCTION_.
  3. Select the PowerTag entity you want to add (ends with _'total energy'_)
  4. _SAVE_
+
+### Removing old devices
+
+When a wireless device is removed from the gateway or replaced by another one
+(e.g. a faulty PowerTag swapped for a new unit), its old device stays behind in Home Assistant.
+
+ 1. Remove it from the gateway first, then reload the integration.
+ 2. Open the old device (_Settings_ > _Devices & Services_ > _PowerTag Link Gateway_).
+ 3. _⋮_ > _Delete_
+
+Deleting is only allowed for devices that the gateway no longer reports: a device that is still
+present on the gateway would simply be re-created on the next reload.

custom_components/powertag_gateway/__init__.py

@@ -8,11 +8,13 @@
 from homeassistant.const import Platform, CONF_HOST, CONF_PORT, CONF_INTERNAL_URL
 from homeassistant.core import HomeAssistant
 from homeassistant.exceptions import ConfigEntryNotReady
+from homeassistant.helpers import device_registry as dr
 from pymodbus.exceptions import ConnectionException
 
 from .const import (
     CONF_CLIENT,
     CONF_SETUP_LOCK,
+    CONF_PRESENT_DEVICES,
     DOMAIN,
     CONF_TYPE_OF_GATEWAY,
     CONF_DEVICE_UNIQUE_ID_VERSION,
@@ -60,13 +62,34 @@ async def async_setup_entry(hass: HomeAssistant, entry: ConfigEntry) -> bool:
         CONF_DEVICE_UNIQUE_ID_VERSION: unique_id_version,
         # Platforms scan the gateway one after another, see async_setup_entities.
         CONF_SETUP_LOCK: asyncio.Lock(),
+        # Identifiers of the devices found on the gateway during the last scan,
+        # see async_remove_config_entry_device.
+        CONF_PRESENT_DEVICES: set(),
     }
 
     await hass.config_entries.async_forward_entry_setups(entry, PLATFORMS)
 
     return True
 
 
+async def async_remove_config_entry_device(
+    hass: HomeAssistant, entry: ConfigEntry, device_entry: dr.DeviceEntry
+) -> bool:
+    """Allow removing a device from the UI once it is no longer on the gateway.
+
+    Devices that were removed or replaced in the gateway (e.g. a faulty PowerTag
+    swapped for a new one) otherwise stay behind in the device registry forever.
+    A device that the gateway still reports is refused, as it would simply be
+    re-created on the next reload.
+    """
+    data = hass.data.get(DOMAIN, {}).get(entry.entry_id)
+    if data is None:
+        # Entry not loaded: we cannot tell what is on the gateway, be safe.
+        return False
+    present = data[CONF_PRESENT_DEVICES]
+    return not any(identifier in present for identifier in device_entry.identifiers)
+
+
 async def async_unload_entry(hass: HomeAssistant, entry: ConfigEntry) -> bool:
     data = hass.data.get(DOMAIN, {}).get(entry.entry_id)
     if data is None:

custom_components/powertag_gateway/const.py

@@ -18,3 +18,4 @@
 DPWS_FRIENDLY_NAME = 'FriendlyName'
 DPWS_SERIAL_NUMBER = 'SerialNumber'
 CONF_SETUP_LOCK = 'setup_lock'
+CONF_PRESENT_DEVICES = 'present_devices'

custom_components/powertag_gateway/entity_base.py

@@ -10,7 +10,13 @@
 from homeassistant.helpers import device_registry as dr
 
 from . import UniqueIdVersion
-from .const import CONF_CLIENT, DOMAIN, CONF_DEVICE_UNIQUE_ID_VERSION, CONF_SETUP_LOCK
+from .const import (
+    CONF_CLIENT,
+    DOMAIN,
+    CONF_DEVICE_UNIQUE_ID_VERSION,
+    CONF_SETUP_LOCK,
+    CONF_PRESENT_DEVICES,
+)
 from .const import GATEWAY_DOMAIN, TAG_DOMAIN
 from .device_features import (
     FeatureClass,
@@ -281,6 +287,7 @@ async def _async_setup_entities(
     client = data[CONF_CLIENT]
     presentation_url = data[CONF_INTERNAL_URL]
     device_unique_id_version = data[CONF_DEVICE_UNIQUE_ID_VERSION]
+    present_devices: set = data[CONF_PRESENT_DEVICES]
 
     entities = []
     gateway_device = await gateway_device_info(client, presentation_url)
@@ -296,6 +303,7 @@ async def _async_setup_entities(
         configuration_url=gateway_device.get("configuration_url"),
         serial_number=gateway_device.get("serial_number"),
     )
+    present_devices.update(gateway_device["identifiers"])
 
     _LOGGER.debug("Starting to scan for devices...")
     for i in range(1, 100):
@@ -366,6 +374,7 @@ async def _async_setup_entities(
         )
         if tag_device is None:
             continue
+        present_devices.update(tag_device["identifiers"])
 
         device_name = tag_device["name"]