Add multiprocessing.reduction submodule (#7361)

stdlib/multiprocessing/__init__.pyi

@@ -1,7 +1,7 @@
 import sys
 from collections.abc import Callable, Iterable
 from logging import Logger
-from multiprocessing import connection, context, pool, synchronize
+from multiprocessing import connection, context, pool, reduction as reducer, synchronize
 from multiprocessing.context import (
     AuthenticationError as AuthenticationError,
     BaseContext,

stdlib/multiprocessing/reduction.pyi

@@ -0,0 +1,84 @@
+import pickle
+import sys
+from abc import ABCMeta
+from copyreg import _DispatchTableType
+from typing import Any
+from typing_extensions import Literal
+
+if sys.platform == "win32":
+    __all__ = ["send_handle", "recv_handle", "ForkingPickler", "register", "dump", "DupHandle", "duplicate", "steal_handle"]
+else:
+    __all__ = ["send_handle", "recv_handle", "ForkingPickler", "register", "dump", "DupFd", "sendfds", "recvfds"]
+
+class ForkingPickler(pickle.Pickler):
+    dispatch_table: _DispatchTableType
+    def __init__(self, *args) -> None: ...
+    @classmethod
+    def register(cls, type, reduce) -> None: ...
+    @classmethod
+    def dumps(cls, obj, protocol: Any | None = ...): ...
+    loads = pickle.loads
+
+register = ForkingPickler.register
+
+def dump(obj, file, protocol: Any | None = ...) -> None: ...
+
+if sys.platform == "win32":
+    if sys.version_info >= (3, 8):
+        def duplicate(handle, target_process: Any | None = ..., inheritable: bool = ..., *, source_process: Any | None = ...): ...
+    else:
+        def duplicate(handle, target_process: Any | None = ..., inheritable: bool = ...): ...
+
+    def steal_handle(source_pid, handle): ...
+    def send_handle(conn, handle, destination_pid) -> None: ...
+    def recv_handle(conn): ...
+
+    class DupHandle:
+        def __init__(self, handle, access, pid: Any | None = ...) -> None: ...
+        def detach(self): ...
+
+else:
+    if sys.platform == "darwin":
+        ACKNOWLEDGE: Literal[True]
+    else:
+        ACKNOWLEDGE: Literal[False]
+
+    def recvfds(sock, size): ...
+    def send_handle(conn, handle, destination_pid) -> None: ...
+    def recv_handle(conn) -> None: ...
+    def sendfds(sock, fds) -> None: ...
+    def DupFd(fd): ...
+
+# These aliases are to work around pyright complaints.
+# Pyright doesn't like it when a class object is defined as an alias
+# of a global object with the same name.
+_ForkingPickler = ForkingPickler
+_register = register
+_dump = dump
+_send_handle = send_handle
+_recv_handle = recv_handle
+
+if sys.platform == "win32":
+    _steal_handle = steal_handle
+    _duplicate = duplicate
+    _DupHandle = DupHandle
+else:
+    _sendfds = sendfds
+    _recvfds = recvfds
+    _DupFd = DupFd
+
+class AbstractReducer(metaclass=ABCMeta):
+    ForkingPickler = _ForkingPickler
+    register = _register
+    dump = _dump
+    send_handle = _send_handle
+    recv_handle = _recv_handle
+    if sys.platform == "win32":
+        steal_handle = _steal_handle
+        duplicate = _duplicate
+        DupHandle = _DupHandle
+    else:
+        sendfds = _sendfds
+        recvfds = _recvfds
+        DupFd = _DupFd
+    def __init__(self, *args) -> None: ...