Sync pre-release CPython main branch from GitHub (2026-06-04)

Summary:
Imported python/cpython `3.16.0a0` from upstream rev [`e28a2f4`](https://www.github.com/python/cpython/commit/e28a2f493044ecfc0f76fe78ff6dde8e395504a9) (committed 2026-06-04 20:37:18+00:00).

# Commit Info

- Base: (`3.16.0a0`) - [`57d4446`](https://www.github.com/python/cpython/commit/57d444612d9c8a0eab66543d5bf8539103a59b47) (commit date: 2026-06-04 00:00:51+00:00)
- Imported: (`3.16.0a0`) - [`e28a2f4`](https://www.github.com/python/cpython/commit/e28a2f493044ecfc0f76fe78ff6dde8e395504a9) (commit date: 2026-06-04 20:37:18+00:00)

# Noteworthy file changes

- Low-signal files (8 added) (NEWS.d, docs, .github)

Complete list of added/removed files: https://www.internalfb.com/intern/everpaste/?color=0&handle=GPQGPShGeRXJEqEEAJilEKcc3pYXbr0LAAAz

Differential Revision: D107613581

fbshipit-source-id: dbe62ccba45e6870d04eaacb6c0e11695f861b10

Author: generatedunixname1734921407115435

Doc/c-api/complex.rst

@@ -130,7 +130,7 @@ rather than dereferencing them through pointers.
 
 Please note, that these functions are :term:`soft deprecated` since Python
 3.15.  Avoid using this API in a new code to do complex arithmetic: either use
-the `Number Protocol <number>`_ API or use native complex types, like
+the :ref:`Number Protocol <number>` API or use native complex types, like
 :c:expr:`double complex`.
 
 

Doc/extending/first-extension-module.rst

@@ -164,7 +164,7 @@ Then, create ``meson.build`` containing the following:
 
 .. note::
 
-   See `meson-python documentation <meson-python>`_ for details on
+   See the `meson-python documentation <meson-python_>`_ for details on
    configuration.
 
 Now, build install the *project in the current directory* (``.``) via ``pip``:

Doc/library/shlex.rst

@@ -44,12 +44,15 @@ The :mod:`!shlex` module defines the following functions:
    .. versionadded:: 3.8
 
 
-.. function:: quote(s)
+.. function:: quote(s, *, force=False)
 
    Return a shell-escaped version of the string *s*.  The returned value is a
    string that can safely be used as one token in a shell command line, for
    cases where you cannot use a list.
 
+   If *force* is :const:`True`, then *s* is unconditionally quoted,
+   even if it is already safe for a shell without being quoted.
+
    .. _shlex-quote-warning:
 
    .. warning::
@@ -91,8 +94,23 @@ The :mod:`!shlex` module defines the following functions:
       >>> command
       ['ls', '-l', 'somefile; rm -rf ~']
 
+   The *force* keyword can be used to produce consistent behavior when
+   escaping multiple strings:
+
+      >>> from shlex import quote
+      >>> filenames = ['my first file', 'file2', 'file 3']
+      >>> filenames_some_escaped = [quote(f) for f in filenames]
+      >>> filenames_some_escaped
+      ["'my first file'", 'file2', "'file 3'"]
+      >>> filenames_all_escaped = [quote(f, force=True) for f in filenames]
+      >>> filenames_all_escaped
+      ["'my first file'", "'file2'", "'file 3'"]
+
    .. versionadded:: 3.3
 
+   .. versionchanged:: next
+      The *force* keyword was added.
+
 The :mod:`!shlex` module defines the following class:
 
 

Doc/library/stdtypes.rst

@@ -2616,7 +2616,9 @@ expression support in the :mod:`re` module).
    :func:`re.split`). Splitting an empty string with a specified separator
    returns ``['']``.
 
-   For example::
+   For example:
+
+   .. doctest::
 
       >>> '1,2,3'.split(',')
       ['1', '2', '3']
@@ -2634,7 +2636,9 @@ expression support in the :mod:`re` module).
    string or a string consisting of just whitespace with a ``None`` separator
    returns ``[]``.
 
-   For example::
+   For example:
+
+   .. doctest::
 
       >>> '1 2 3'.split()
       ['1', '2', '3']
@@ -2646,7 +2650,9 @@ expression support in the :mod:`re` module).
    If *sep* is not specified or is ``None`` and  *maxsplit* is ``0``, only
    leading runs of consecutive whitespace are considered.
 
-   For example::
+   For example:
+
+   .. doctest::
 
       >>> "".split(None, 0)
       []
@@ -2655,7 +2661,7 @@ expression support in the :mod:`re` module).
       >>> "   foo   ".split(maxsplit=0)
       ['foo   ']
 
-   See also :meth:`join`.
+   See also :meth:`join` and :meth:`rsplit`.
 
 
 .. index::

Doc/using/windows.rst

@@ -455,6 +455,12 @@ customization.
        Python runtimes, or false to prevent it.
        By default, true.
 
+   * - ``shebang_templates``
+     - (none)
+     - Mapping from shebang line template to alternative command, such as
+       ``py -V:<tag>`` or a substitute string.
+       See :ref:`pymanager-shebang` for more details.
+
    * - ``log_level``
      - ``PYMANAGER_VERBOSE``, ``PYMANAGER_DEBUG``
      - Set the default level of output (0-50).
@@ -568,6 +574,30 @@ which the path to the script and any additional arguments will be appended.
 This functionality may be disabled by the ``shebang_can_run_anything``
 configuration option.
 
+Since version 26.3 of the Python install manager, custom shebang templates may
+be added to your configuration file. Add the ``shebang_templates`` object with
+one member for each template (the string to match) and the command to use when
+the template is matched. Most commands should be ``py -V:<tag>`` (or ``pyw``) to
+launch one of your installed runtimes. The ``py -3.<version>`` form is also
+allowed, as is a plain ``py`` to launch the default. No other arguments are
+supported.
+
+.. code:: json5
+
+   {
+       "shebang_templates": {
+           "/usr/bin/python": "py",
+           "/usr/bin/my_custom_python": "py -V:MyCustomPython/3"
+       }
+   }
+
+If the substitute command is not ``py`` or ``pyw``, it will be written back into
+the shebang and regular handling continues. If launching arbitrary executables
+is permitted, then providing a full path will allow you to redirect from Python
+to any executable. The template should match either the entire line (ignoring
+leading and trailing whitespace), or up to the first space in the shebang line.
+
+
 .. note::
 
    The behaviour of shebangs in the Python install manager is subtly different

Doc/whatsnew/3.16.rst

@@ -109,6 +109,13 @@ os
   process via a pidfd.  Available on Linux 5.6+.
   (Contributed by Maurycy Pawłowski-Wieroński in :gh:`149464`.)
 
+shlex
+-----
+
+* Add keyword-only parameter *force* to :func:`shlex.quote` to force quoting
+  a string, even if it is already safe for a shell without being quoted.
+  (Contributed by Jay Berry in :gh:`148846`.)
+
 xml
 ---
 

Lib/enum.py

@@ -1620,32 +1620,38 @@ def __or__(self, other):
         if other_value is NotImplemented:
             return NotImplemented
 
-        for flag in self, other:
-            if self._get_value(flag) is None:
-                raise TypeError(f"'{flag}' cannot be combined with other flags with |")
         value = self._value_
+        # _get_value(self) is self._value_ and _get_value(other) is
+        # other_value, so only walk the operands (to raise on the offending
+        # flag) when one of those values is actually None.
+        if value is None or other_value is None:
+            for flag in self, other:
+                if self._get_value(flag) is None:
+                    raise TypeError(f"'{flag}' cannot be combined with other flags with |")
         return self.__class__(value | other_value)
 
     def __and__(self, other):
         other_value = self._get_value(other)
         if other_value is NotImplemented:
             return NotImplemented
 
-        for flag in self, other:
-            if self._get_value(flag) is None:
-                raise TypeError(f"'{flag}' cannot be combined with other flags with &")
         value = self._value_
+        if value is None or other_value is None:
+            for flag in self, other:
+                if self._get_value(flag) is None:
+                    raise TypeError(f"'{flag}' cannot be combined with other flags with &")
         return self.__class__(value & other_value)
 
     def __xor__(self, other):
         other_value = self._get_value(other)
         if other_value is NotImplemented:
             return NotImplemented
 
-        for flag in self, other:
-            if self._get_value(flag) is None:
-                raise TypeError(f"'{flag}' cannot be combined with other flags with ^")
         value = self._value_
+        if value is None or other_value is None:
+            for flag in self, other:
+                if self._get_value(flag) is None:
+                    raise TypeError(f"'{flag}' cannot be combined with other flags with ^")
         return self.__class__(value ^ other_value)
 
     def __invert__(self):

Lib/importlib/_bootstrap.py

@@ -20,12 +20,6 @@
 # reference any injected objects! This includes not only global code but also
 # anything specified at the class level.
 
-def _object_name(obj):
-    try:
-        return obj.__qualname__
-    except AttributeError:
-        return type(obj).__qualname__
-
 # Bootstrap-related code ######################################################
 
 # Modules injected manually by _setup()

Lib/logging/__init__.py

@@ -1373,9 +1373,16 @@ def getLogger(self, name):
         logger and fix up the parent/child references which pointed to the
         placeholder to now point to the logger.
         """
-        rv = None
         if not isinstance(name, str):
             raise TypeError('A logger name must be a string')
+        # Fast path: an already-registered, non-placeholder logger can be
+        # returned without taking the lock. dict.get() is atomic under both
+        # the GIL and free threading, and a Logger is fully initialised before
+        # being inserted into loggerDict under the lock, so this never sees a
+        # partially-constructed object.
+        rv = self.loggerDict.get(name)
+        if rv is not None and not isinstance(rv, PlaceHolder):
+            return rv
         with _lock:
             if name in self.loggerDict:
                 rv = self.loggerDict[name]

Lib/logging/handlers.py

@@ -282,7 +282,16 @@ def __init__(self, filename, when='h', interval=1, backupCount=0,
         # path object (see Issue #27493), but self.baseFilename will be a string
         filename = self.baseFilename
         if os.path.exists(filename):
-            t = int(os.stat(filename).st_mtime)
+            # Use the minimum of file creation and modification time as
+            # the base of the rollover calculation
+            stat_result = os.stat(filename)
+            # Use st_birthtime whenever it is available or use st_ctime
+            # instead otherwise
+            try:
+                creation_time = stat_result.st_birthtime
+            except AttributeError:
+                creation_time = stat_result.st_ctime
+            t = int(min(creation_time, stat_result.st_mtime))
         else:
             t = int(time.time())
         self.rolloverAt = self.computeRollover(t)