Restored ability to connect IPv6-only host.

CHANGES/6195.bugfix

@@ -0,0 +1 @@
+Restored ability to connect IPv6-only host.

aiohttp/resolver.py

@@ -40,17 +40,23 @@ async def resolve(
         hosts = []
         for family, _, proto, _, address in infos:
             if family == socket.AF_INET6:
-                if not (socket.has_ipv6 and address[3]):  # type: ignore[misc]
+                if len(address) < 3:
+                    # IPv6 is not supported by Python build,
+                    # or IPv6 is not enabled in the host
                     continue
-                # This is essential for link-local IPv6 addresses.
-                # LL IPv6 is a VERY rare case. Strictly speaking, we should use
-                # getnameinfo() unconditionally, but performance makes sense.
-                host, _port = socket.getnameinfo(
-                    address, socket.NI_NUMERICHOST | socket.NI_NUMERICSERV
-                )
-                port = int(_port)
-            else:
-                host, port = address[:2]
+                if address[3]:  # type: ignore[misc]
+                    # This is essential for link-local IPv6 addresses.
+                    # LL IPv6 is a VERY rare case. Strictly speaking, we should use
+                    # getnameinfo() unconditionally, but performance makes sense.
+                    host, _port = socket.getnameinfo(
+                        address, socket.NI_NUMERICHOST | socket.NI_NUMERICSERV
+                    )
+                    port = int(_port)
+                else:
+                    host, port = address[:2]
+            else:  # IPv4
+                assert family == socket.AF_INET
+                host, port = address  # type: ignore[misc]
             hosts.append(
                 {
                     "hostname": hostname,

tests/test_resolver.py

@@ -44,7 +44,7 @@ async def fake(*args: Any, **kwargs: Any) -> List[Any]:
         if not hosts:
             raise socket.gaierror
 
-        return [(None, None, None, None, [h, 0]) for h in hosts]
+        return [(socket.AF_INET, None, socket.SOCK_STREAM, None, [h, 0]) for h in hosts]
 
     return fake