Merge branch 'main' into typewatch

* main:
  Minor edits to the Descriptor HowTo Guide (pythonGH-24901)
  Fix link to Lifecycle of a Pull Request in CONTRIBUTING (python#98102)
  pythonGH-94597: deprecate `SafeChildWatcher`, `FastChildWatcher` and `MultiLoopChildWatcher` child watchers  (python#98089)
  Auto-cancel old builds when new commit pushed to branch (python#98009)
  pythongh-95011: Migrate syslog module to Argument Clinic (pythonGH-95012)

.github/CONTRIBUTING.rst

@@ -38,7 +38,7 @@ also suggestions on how you can most effectively help the project.
 
 Please be aware that our workflow does deviate slightly from the typical GitHub
 project. Details on how to properly submit a pull request are covered in
-`Lifecycle of a Pull Request <https://devguide.python.org/pullrequest/>`_.
+`Lifecycle of a Pull Request <https://devguide.python.org/getting-started/pull-request-lifecycle.html>`_.
 We utilize various bots and status checks to help with this, so do follow the
 comments they leave and their "Details" links, respectively. The key points of
 our workflow that are not covered by a bot or status check are:

.github/workflows/build.yml

@@ -25,6 +25,10 @@ on:
 permissions:
   contents: read
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
 jobs:
   check_source:
     name: 'Check for source changes'

.github/workflows/build_msi.yml

@@ -18,6 +18,10 @@ on:
 permissions:
   contents: read
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
 jobs:
   build:
     name: Windows Installer

.github/workflows/doc.yml

@@ -28,6 +28,10 @@ on:
 permissions:
   contents: read
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
 jobs:
   build_doc:
     name: 'Docs'

.github/workflows/verify-ensurepip-wheels.yml

@@ -16,6 +16,10 @@ on:
 permissions:
   contents: read
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
 jobs:
   verify:
     runs-on: ubuntu-latest

Doc/howto/descriptor.rst

@@ -847,7 +847,7 @@ afterwards, :meth:`__set_name__` will need to be called manually.
 ORM example
 -----------
 
-The following code is simplified skeleton showing how data descriptors could
+The following code is a simplified skeleton showing how data descriptors could
 be used to implement an `object relational mapping
 <https://en.wikipedia.org/wiki/Object%E2%80%93relational_mapping>`_.
 
@@ -1535,6 +1535,8 @@ by member descriptors:
         def __get__(self, obj, objtype=None):
             'Emulate member_get() in Objects/descrobject.c'
             # Also see PyMember_GetOne() in Python/structmember.c
+            if obj is None:
+                return self
             value = obj._slotvalues[self.offset]
             if value is null:
                 raise AttributeError(self.name)
@@ -1563,13 +1565,13 @@ variables:
     class Type(type):
         'Simulate how the type metaclass adds member objects for slots'
 
-        def __new__(mcls, clsname, bases, mapping):
+        def __new__(mcls, clsname, bases, mapping, **kwargs):
             'Emulate type_new() in Objects/typeobject.c'
             # type_new() calls PyTypeReady() which calls add_methods()
             slot_names = mapping.get('slot_names', [])
             for offset, name in enumerate(slot_names):
                 mapping[name] = Member(name, clsname, offset)
-            return type.__new__(mcls, clsname, bases, mapping)
+            return type.__new__(mcls, clsname, bases, mapping, **kwargs)
 
 The :meth:`object.__new__` method takes care of creating instances that have
 slots instead of an instance dictionary.  Here is a rough simulation in pure
@@ -1580,7 +1582,7 @@ Python:
     class Object:
         'Simulate how object.__new__() allocates memory for __slots__'
 
-        def __new__(cls, *args):
+        def __new__(cls, *args, **kwargs):
             'Emulate object_new() in Objects/typeobject.c'
             inst = super().__new__(cls)
             if hasattr(cls, 'slot_names'):
@@ -1593,7 +1595,7 @@ Python:
             cls = type(self)
             if hasattr(cls, 'slot_names') and name not in cls.slot_names:
                 raise AttributeError(
-                    f'{type(self).__name__!r} object has no attribute {name!r}'
+                    f'{cls.__name__!r} object has no attribute {name!r}'
                 )
             super().__setattr__(name, value)
 
@@ -1602,7 +1604,7 @@ Python:
             cls = type(self)
             if hasattr(cls, 'slot_names') and name not in cls.slot_names:
                 raise AttributeError(
-                    f'{type(self).__name__!r} object has no attribute {name!r}'
+                    f'{cls.__name__!r} object has no attribute {name!r}'
                 )
             super().__delattr__(name)
 

Doc/whatsnew/3.12.rst

@@ -109,6 +109,24 @@ New Modules
 Improved Modules
 ================
 
+asyncio
+-------
+
+* On Linux, :mod:`asyncio` uses :class:`~asyncio.PidfdChildWatcher` by default
+  if :func:`os.pidfd_open` is available and functional instead of
+  :class:`~asyncio.ThreadedChildWatcher`.
+  (Contributed by Kumar Aditya in :gh:`98024`.)
+
+* The child watcher classes :class:`~asyncio.MultiLoopChildWatcher`,
+  :class:`~asyncio.FastChildWatcher` and
+  :class:`~asyncio.SafeChildWatcher` are deprecated and
+  will be removed in Python 3.14. It is recommended to not manually
+  configure a child watcher as the event loop now uses the best available
+  child watcher for each platform (:class:`~asyncio.PidfdChildWatcher`
+  if supported and :class:`~asyncio.ThreadedChildWatcher` otherwise).
+  (Contributed by Kumar Aditya in :gh:`94597`.)
+
+
 pathlib
 -------
 

Include/internal/pycore_global_strings.h

@@ -350,6 +350,7 @@ struct _Py_global_strings {
         STRUCT_FOR_ID(exception)
         STRUCT_FOR_ID(exp)
         STRUCT_FOR_ID(extend)
+        STRUCT_FOR_ID(facility)
         STRUCT_FOR_ID(factory)
         STRUCT_FOR_ID(family)
         STRUCT_FOR_ID(fanout)
@@ -392,6 +393,7 @@ struct _Py_global_strings {
         STRUCT_FOR_ID(hi)
         STRUCT_FOR_ID(hook)
         STRUCT_FOR_ID(id)
+        STRUCT_FOR_ID(ident)
         STRUCT_FOR_ID(ignore)
         STRUCT_FOR_ID(imag)
         STRUCT_FOR_ID(importlib)
@@ -447,6 +449,7 @@ struct _Py_global_strings {
         STRUCT_FOR_ID(lo)
         STRUCT_FOR_ID(locale)
         STRUCT_FOR_ID(locals)
+        STRUCT_FOR_ID(logoption)
         STRUCT_FOR_ID(loop)
         STRUCT_FOR_ID(mapping)
         STRUCT_FOR_ID(match)

Lib/asyncio/unix_events.py

@@ -1022,6 +1022,13 @@ class SafeChildWatcher(BaseChildWatcher):
     big number of children (O(n) each time SIGCHLD is raised)
     """
 
+    def __init__(self):
+        super().__init__()
+        warnings._deprecated("SafeChildWatcher",
+                             "{name!r} is deprecated as of Python 3.12 and will be "
+                             "removed in Python {remove}.",
+                              remove=(3, 14))
+
     def close(self):
         self._callbacks.clear()
         super().close()
@@ -1100,6 +1107,10 @@ def __init__(self):
         self._lock = threading.Lock()
         self._zombies = {}
         self._forks = 0
+        warnings._deprecated("FastChildWatcher",
+                             "{name!r} is deprecated as of Python 3.12 and will be "
+                             "removed in Python {remove}.",
+                              remove=(3, 14))
 
     def close(self):
         self._callbacks.clear()
@@ -1212,6 +1223,10 @@ class MultiLoopChildWatcher(AbstractChildWatcher):
     def __init__(self):
         self._callbacks = {}
         self._saved_sighandler = None
+        warnings._deprecated("MultiLoopChildWatcher",
+                             "{name!r} is deprecated as of Python 3.12 and will be "
+                             "removed in Python {remove}.",
+                              remove=(3, 14))
 
     def is_active(self):
         return self._saved_sighandler is not None

Lib/test/test_asyncio/test_events.py

@@ -22,7 +22,7 @@
 import unittest
 from unittest import mock
 import weakref
-
+import warnings
 if sys.platform not in ('win32', 'vxworks'):
     import tty
 
@@ -2055,7 +2055,9 @@ def test_remove_fds_after_closing(self):
     class UnixEventLoopTestsMixin(EventLoopTestsMixin):
         def setUp(self):
             super().setUp()
-            watcher = asyncio.SafeChildWatcher()
+            with warnings.catch_warnings():
+                warnings.simplefilter('ignore', DeprecationWarning)
+                watcher = asyncio.SafeChildWatcher()
             watcher.attach_loop(self.loop)
             asyncio.set_child_watcher(watcher)
 
@@ -2652,7 +2654,9 @@ def setUp(self):
         asyncio.set_event_loop(self.loop)
 
         if sys.platform != 'win32':
-            watcher = asyncio.SafeChildWatcher()
+            with warnings.catch_warnings():
+                warnings.simplefilter('ignore', DeprecationWarning)
+                watcher = asyncio.SafeChildWatcher()
             watcher.attach_loop(self.loop)
             asyncio.set_child_watcher(watcher)
 

Lib/test/test_asyncio/test_streams.py

@@ -9,6 +9,7 @@
 import threading
 import unittest
 from unittest import mock
+import warnings
 from test.support import socket_helper
 try:
     import ssl
@@ -791,8 +792,9 @@ def test_read_all_from_pipe_reader(self):
         protocol = asyncio.StreamReaderProtocol(reader, loop=self.loop)
         transport, _ = self.loop.run_until_complete(
             self.loop.connect_read_pipe(lambda: protocol, pipe))
-
-        watcher = asyncio.SafeChildWatcher()
+        with warnings.catch_warnings():
+            warnings.simplefilter('ignore', DeprecationWarning)
+            watcher = asyncio.SafeChildWatcher()
         watcher.attach_loop(self.loop)
         try:
             asyncio.set_child_watcher(watcher)