Fix writing network settings with missing TX power

bellows/zigbee/application.py

@@ -73,6 +73,8 @@
     "54:EF:44": 0x115F,  # Lumi
 }
 
+DEFAULT_TX_POWER = 8  # dBm
+
 LIB_VERSION = importlib.metadata.version("bellows")
 LOGGER = logging.getLogger(__name__)
 
@@ -522,7 +524,11 @@ async def write_network_info(
         parameters = t.EmberNetworkParameters()
         parameters.panId = t.EmberPanId(network_info.pan_id)
         parameters.extendedPanId = t.EUI64(network_info.extended_pan_id)
-        parameters.radioTxPower = t.uint8_t(network_info.tx_power)
+        parameters.radioTxPower = (
+            t.uint8_t(network_info.tx_power)
+            if network_info.tx_power is not None
+            else DEFAULT_TX_POWER
+        )
         parameters.radioChannel = t.uint8_t(network_info.channel)
         parameters.joinMethod = t.EmberJoinMethod.USE_MAC_ASSOCIATION
         parameters.nwkManagerId = t.EmberNodeId(network_info.nwk_manager_id)

tests/test_application.py

@@ -28,7 +28,7 @@
 import bellows.types.struct
 import bellows.uart as uart
 import bellows.zigbee.application
-from bellows.zigbee.application import ControllerApplication
+from bellows.zigbee.application import DEFAULT_TX_POWER, ControllerApplication
 import bellows.zigbee.device
 from bellows.zigbee.device import EZSPEndpoint, EZSPGroupEndpoint
 from bellows.zigbee.util import map_rssi_to_energy
@@ -2251,6 +2251,37 @@ async def test_write_network_info(
     ]
 
 
+async def test_write_network_info_with_none_tx_power(
+    app: ControllerApplication,
+    ieee: zigpy_t.EUI64,
+    zigpy_backup: zigpy.backups.NetworkBackup,
+) -> None:
+    """Test that write_network_info uses DEFAULT_TX_POWER when tx_power is None."""
+    network_info = zigpy_backup.network_info.replace(tx_power=None)
+
+    with patch.object(app, "_reset"):
+        await app.write_network_info(
+            node_info=zigpy_backup.node_info,
+            network_info=network_info,
+        )
+
+    # Verify formNetwork was called with DEFAULT_TX_POWER instead of None
+    assert app._ezsp._protocol.formNetwork.mock_calls == [
+        call(
+            parameters=t.EmberNetworkParameters(
+                panId=network_info.pan_id,
+                extendedPanId=network_info.extended_pan_id,
+                radioTxPower=DEFAULT_TX_POWER,
+                radioChannel=network_info.channel,
+                joinMethod=t.EmberJoinMethod.USE_MAC_ASSOCIATION,
+                nwkManagerId=t.EmberNodeId(0x0000),
+                nwkUpdateId=network_info.nwk_update_id,
+                channels=network_info.channel_mask,
+            )
+        )
+    ]
+
+
 async def test_write_network_info_restores_route_table(
     app: ControllerApplication,
     ieee: zigpy_t.EUI64,