Update discover single to handle hostnames (#539)

kasa/discover.py

@@ -1,6 +1,7 @@
 """Discovery module for TP-Link Smart Home devices."""
 import asyncio
 import binascii
+import ipaddress
 import logging
 import socket
 from typing import Awaitable, Callable, Dict, Optional, Type, cast
@@ -273,9 +274,34 @@ class Discover:
         """
         loop = asyncio.get_event_loop()
         event = asyncio.Event()
+
+        try:
+            ipaddress.ip_address(host)
+            ip = host
+        except ValueError:
+            try:
+                adrrinfo = await loop.getaddrinfo(
+                    host,
+                    0,
+                    type=socket.SOCK_DGRAM,
+                    family=socket.AF_INET,
+                )
+                # getaddrinfo returns a list of 5 tuples with the following structure:
+                # (family, type, proto, canonname, sockaddr)
+                # where sockaddr is 2 tuple (ip, port).
+                # hence [0][4][0] is a stable array access because if no socket
+                # address matches the host for SOCK_DGRAM AF_INET the gaierror
+                # would be raised.
+                # https://docs.python.org/3/library/socket.html#socket.getaddrinfo
+                ip = adrrinfo[0][4][0]
+            except socket.gaierror as gex:
+                raise SmartDeviceException(
+                    f"Could not resolve hostname {host}"
+                ) from gex
+
         transport, protocol = await loop.create_datagram_endpoint(
             lambda: _DiscoverProtocol(
-                target=host,
+                target=ip,
                 port=port,
                 discovered_event=event,
                 credentials=credentials,
@@ -297,16 +323,17 @@ class Discover:
         finally:
             transport.close()
 
-        if host in protocol.discovered_devices:
-            dev = protocol.discovered_devices[host]
+        if ip in protocol.discovered_devices:
+            dev = protocol.discovered_devices[ip]
+            dev.host = host
             await dev.update()
             return dev
-        elif host in protocol.unsupported_devices:
+        elif ip in protocol.unsupported_devices:
             raise UnsupportedDeviceException(
-                f"Unsupported device {host}: {protocol.unsupported_devices[host]}"
+                f"Unsupported device {host}: {protocol.unsupported_devices[ip]}"
             )
-        elif host in protocol.invalid_device_exceptions:
-            raise protocol.invalid_device_exceptions[host]
+        elif ip in protocol.invalid_device_exceptions:
+            raise protocol.invalid_device_exceptions[ip]
         else:
             raise SmartDeviceException(f"Unable to get discovery response for {host}")
 

kasa/tests/test_discovery.py

@@ -1,5 +1,6 @@
 # type: ignore
 import re
+import socket
 import sys
 
 import pytest  # type: ignore # https://github.com/pytest-dev/pytest/issues/3342
@@ -74,6 +75,31 @@ async def test_discover_single(discovery_data: dict, mocker, custom_port):
     assert x.port == custom_port or x.port == 9999
 
 
+async def test_discover_single_hostname(discovery_data: dict, mocker):
+    """Make sure that discover_single returns an initialized SmartDevice instance."""
+    host = "foobar"
+    ip = "127.0.0.1"
+
+    def mock_discover(self):
+        self.datagram_received(
+            protocol.TPLinkSmartHomeProtocol.encrypt(json_dumps(discovery_data))[4:],
+            (ip, 9999),
+        )
+
+    mocker.patch.object(_DiscoverProtocol, "do_discover", mock_discover)
+    mocker.patch("kasa.TPLinkSmartHomeProtocol.query", return_value=discovery_data)
+    mocker.patch("socket.getaddrinfo", return_value=[(None, None, None, None, (ip, 0))])
+
+    x = await Discover.discover_single(host)
+    assert issubclass(x.__class__, SmartDevice)
+    assert x._sys_info is not None
+    assert x.host == host
+
+    mocker.patch("socket.getaddrinfo", side_effect=socket.gaierror())
+    with pytest.raises(SmartDeviceException):
+        x = await Discover.discover_single(host)
+
+
 @pytest.mark.parametrize("custom_port", [123, None])
 async def test_connect_single(discovery_data: dict, mocker, custom_port):
     """Make sure that connect_single returns an initialized SmartDevice instance."""