asyncio: allow port=None in create_server when a host is given

create_server passes port straight to getaddrinfo, which accepts None,
so create_server(proto, "localhost", None) works at runtime but the stub
rejected it because the non-sock overload declared port: int.

Widen that parameter to int | None in the six create_server overloads
(three version gates each in base_events.pyi and events.pyi) and add
test cases covering the host/port/sock combinations.

create_connection also has port: int = ..., but it is left alone here:
its port is not optional in the same way.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: ekanshul

stdlib/@tests/test_cases/asyncio/check_create_server.py

@@ -0,0 +1,30 @@
+from __future__ import annotations
+
+import asyncio
+import socket
+from typing_extensions import assert_type
+
+
+async def check_create_server(loop: asyncio.AbstractEventLoop, base_loop: asyncio.BaseEventLoop) -> None:
+    # `port` is optional whenever a host is given: the runtime passes it straight
+    # to getaddrinfo, which treats None as "any port".
+    assert_type(await loop.create_server(asyncio.Protocol, "localhost"), asyncio.Server)
+    assert_type(await loop.create_server(asyncio.Protocol, "localhost", 8080), asyncio.Server)
+    assert_type(await loop.create_server(asyncio.Protocol, "localhost", None), asyncio.Server)
+    assert_type(await loop.create_server(asyncio.Protocol, ["localhost", "127.0.0.1"], 8080), asyncio.Server)
+
+    # A port with no host binds every interface.
+    assert_type(await loop.create_server(asyncio.Protocol, None, 8080), asyncio.Server)
+    assert_type(await loop.create_server(asyncio.Protocol, port=8080), asyncio.Server)
+
+    assert_type(await base_loop.create_server(asyncio.Protocol, "localhost", None), asyncio.Server)
+    assert_type(await base_loop.create_server(asyncio.Protocol, port=8080), asyncio.Server)
+
+
+async def check_create_server_sock(loop: asyncio.AbstractEventLoop, sock: socket.socket) -> None:
+    assert_type(await loop.create_server(asyncio.Protocol, sock=sock), asyncio.Server)
+
+    # The runtime rejects host/port together with sock:
+    # ValueError: host/port and sock can not be specified at the same time
+    await loop.create_server(asyncio.Protocol, "localhost", sock=sock)  # type: ignore
+    await loop.create_server(asyncio.Protocol, None, 8080, sock=sock)  # type: ignore

stdlib/asyncio/base_events.pyi

@@ -244,7 +244,7 @@ class BaseEventLoop(AbstractEventLoop):
             self,
             protocol_factory: _ProtocolFactory,
             host: str | Sequence[str] | None = None,
-            port: int = ...,
+            port: int | None = None,
             *,
             family: int = 0,
             flags: int = 1,
@@ -283,7 +283,7 @@ class BaseEventLoop(AbstractEventLoop):
             self,
             protocol_factory: _ProtocolFactory,
             host: str | Sequence[str] | None = None,
-            port: int = ...,
+            port: int | None = None,
             *,
             family: int = AddressFamily.AF_UNSPEC,
             flags: int = AddressInfo.AI_PASSIVE,
@@ -320,7 +320,7 @@ class BaseEventLoop(AbstractEventLoop):
             self,
             protocol_factory: _ProtocolFactory,
             host: str | Sequence[str] | None = None,
-            port: int = ...,
+            port: int | None = None,
             *,
             family: int = AddressFamily.AF_UNSPEC,
             flags: int = AddressInfo.AI_PASSIVE,

stdlib/asyncio/events.pyi

@@ -299,7 +299,7 @@ class AbstractEventLoop:
             self,
             protocol_factory: _ProtocolFactory,
             host: str | Sequence[str] | None = None,
-            port: int = ...,
+            port: int | None = None,
             *,
             family: int = AddressFamily.AF_UNSPEC,
             flags: int = AddressInfo.AI_PASSIVE,
@@ -340,7 +340,7 @@ class AbstractEventLoop:
             self,
             protocol_factory: _ProtocolFactory,
             host: str | Sequence[str] | None = None,
-            port: int = ...,
+            port: int | None = None,
             *,
             family: int = AddressFamily.AF_UNSPEC,
             flags: int = AddressInfo.AI_PASSIVE,
@@ -379,7 +379,7 @@ class AbstractEventLoop:
             self,
             protocol_factory: _ProtocolFactory,
             host: str | Sequence[str] | None = None,
-            port: int = ...,
+            port: int | None = None,
             *,
             family: int = AddressFamily.AF_UNSPEC,
             flags: int = AddressInfo.AI_PASSIVE,