Fix via_device in fritz linking to itself (#178226)

homeassistant/components/fritz/coordinator.py

@@ -601,6 +601,10 @@ class FritzBoxTools(DataUpdateCoordinator[UpdateCoordinatorDataType]):
             )
             self.mesh_role = MeshRoles.NONE
             for mac, info in hosts.items():
+                # The box lists its own LAN MAC in the Hosts table; skip it so it
+                # is not tracked as a child of itself, as the mesh path does.
+                if dr.format_mac(mac) == self.mac:
+                    continue
                 if self.manage_device_info(info, mac, consider_home):
                     new_device = True
             await self.async_send_signal_device_update(new_device)

tests/components/fritz/test_coordinator.py

@@ -16,6 +16,7 @@ import pytest
 
 from homeassistant.components.fritz.const import (
     CONF_FEATURE_DEVICE_TRACKING,
+    CONF_OLD_DISCOVERY,
     DEFAULT_CONF_FEATURE_DEVICE_TRACKING,
     DEFAULT_SSL,
     DOMAIN,
@@ -695,3 +696,41 @@ async def test_async_trigger_cleanup_preserves_fritz_device(
     )
     assert fritz_device_after is not None
     assert fritz_device_after.id == fritz_device.id
+
+
+async def test_old_discovery_does_not_self_reference_box(
+    hass: HomeAssistant,
+    device_registry: dr.DeviceRegistry,
+    caplog: pytest.LogCaptureFixture,
+    fc_class_mock,
+    fh_class_mock,
+    fs_class_mock,
+) -> None:
+    """Test old discovery does not link the box as its own via device.
+
+    The Hosts table lists the box's own LAN MAC (MOCK_HOST_FRITZBOX). Its MAC
+    connection matches the router device, so tracking it would merge it into the
+    router and resolve via_device_id to itself, which the device registry rejects.
+    """
+    entry = MockConfigEntry(
+        domain=DOMAIN,
+        data=MOCK_USER_DATA,
+        options={CONF_OLD_DISCOVERY: True},
+    )
+    entry.add_to_hass(hass)
+
+    assert await hass.config_entries.async_setup(entry.entry_id)
+    await hass.async_block_till_done(wait_background_tasks=True)
+
+    assert entry.state is ConfigEntryState.LOADED
+
+    router = device_registry.async_get_device(
+        identifiers={(DOMAIN, MOCK_SERIAL_NUMBER)}
+    )
+    assert router is not None
+    assert router.via_device_id is None
+
+    devices = dr.async_entries_for_config_entry(device_registry, entry.entry_id)
+    assert devices
+    for device in devices:
+        assert device.via_device_id != device.id