Avoid calling await getaddrinfo(...) in exception handler (#812)

docs/versionhistory.rst

@@ -3,6 +3,11 @@ Version history
 
 This library adheres to `Semantic Versioning 2.0 <http://semver.org/>`_.
 
+**UNRELEASED**
+
+- Fixed a misleading ``ValueError`` in the context of DNS failures
+  (`#815 <https://github.com/agronholm/anyio/issues/815>`_; PR by @graingert)
+
 **4.6.2**
 
 - Fixed regression caused by (`#807 <https://github.com/agronholm/anyio/pull/807>`_)

src/anyio/_core/_sockets.py

@@ -186,6 +186,14 @@ async def try_connect(remote_host: str, event: Event) -> None:
     try:
         addr_obj = ip_address(remote_host)
     except ValueError:
+        addr_obj = None
+
+    if addr_obj is not None:
+        if isinstance(addr_obj, IPv6Address):
+            target_addrs = [(socket.AF_INET6, addr_obj.compressed)]
+        else:
+            target_addrs = [(socket.AF_INET, addr_obj.compressed)]
+    else:
         # getaddrinfo() will raise an exception if name resolution fails
         gai_res = await getaddrinfo(
             target_host, remote_port, family=family, type=socket.SOCK_STREAM
@@ -194,7 +202,7 @@ async def try_connect(remote_host: str, event: Event) -> None:
         # Organize the list so that the first address is an IPv6 address (if available)
         # and the second one is an IPv4 addresses. The rest can be in whatever order.
         v6_found = v4_found = False
-        target_addrs: list[tuple[socket.AddressFamily, str]] = []
+        target_addrs = []
         for af, *rest, sa in gai_res:
             if af == socket.AF_INET6 and not v6_found:
                 v6_found = True
@@ -204,11 +212,6 @@ async def try_connect(remote_host: str, event: Event) -> None:
                 target_addrs.insert(1, (af, sa[0]))
             else:
                 target_addrs.append((af, sa[0]))
-    else:
-        if isinstance(addr_obj, IPv6Address):
-            target_addrs = [(socket.AF_INET6, addr_obj.compressed)]
-        else:
-            target_addrs = [(socket.AF_INET, addr_obj.compressed)]
 
     oserrors: list[OSError] = []
     async with create_task_group() as tg:

tests/test_sockets.py

@@ -1838,3 +1838,14 @@ async def test_getnameinfo() -> None:
     expected_result = socket.getnameinfo(("127.0.0.1", 6666), 0)
     result = await getnameinfo(("127.0.0.1", 6666))
     assert result == expected_result
+
+
+async def test_connect_tcp_getaddrinfo_context() -> None:
+    """
+    See https://github.com/agronholm/anyio/issues/815
+    """
+    with pytest.raises(socket.gaierror) as exc_info:
+        async with await connect_tcp("anyio.invalid", 6666):
+            pass
+
+    assert exc_info.value.__context__ is None