cpython/Misc/NEWS.d/3.9.0b2.rst

.. bpo: 40904
.. date: 2020-06-08-01-08-57
.. nonce: 76qQzo
.. release date: 2020-06-08
.. section: Core and Builtins

Fix possible segfault in the new PEG parser when parsing f-string containing
yield statements with no value (:code:`f"{yield}"`). Patch by Pablo Galindo

..

.. bpo: 40903
.. date: 2020-06-07-22-50-10
.. nonce: 7dWejS
.. section: Core and Builtins

Fixed a possible segfault in the new PEG parser when producing error
messages for invalid assignments of the form :code:`p=p=`. Patch by Pablo
Galindo

..

.. bpo: 40880
.. date: 2020-06-06-00-23-19
.. nonce: fjdzSh
.. section: Core and Builtins

Fix invalid memory read in the new parser when checking newlines in string
literals. Patch by Pablo Galindo.

..

.. bpo: 40883
.. date: 2020-06-05-23-25-00
.. nonce: M6sQ-Q
.. section: Core and Builtins

Fix memory leak in when parsing f-strings in the new parser. Patch by Pablo
Galindo

..

.. bpo: 40870
.. date: 2020-06-05-12-48-28
.. nonce: 9cd2sk
.. section: Core and Builtins

Raise :exc:`ValueError` when validating custom AST's where the constants
``True``, ``False`` and ``None`` are used within a :class:`ast.Name` node.

..

.. bpo: 40854
.. date: 2020-06-03-13-53-24
.. nonce: O6vfQU
.. section: Core and Builtins

Allow overriding :data:`sys.platlibdir` via a new :envvar:`PYTHONPLATLIBDIR`
environment variable.

..

.. bpo: 40826
.. date: 2020-06-01-20-31-07
.. nonce: XCI4M2
.. section: Core and Builtins

Fix GIL usage in :c:func:`PyOS_Readline`: lock the GIL to set an exception
and pass the Python thread state when checking if there is a pending signal.

..

.. bpo: 40780
.. date: 2020-05-26-17-43-58
.. nonce: 3Ckdgm
.. section: Core and Builtins

Fix a corner case where g-style string formatting of a float failed to
remove trailing zeros.

..

.. bpo: 38964
.. date: 2020-05-25-21-49-11
.. nonce: lrml90
.. section: Core and Builtins

When there's a :exc:`SyntaxError` in the expression part of an fstring, the
filename attribute of the :exc:`SyntaxError` gets correctly set to the name
of the file the fstring resides in.

..

.. bpo: 40750
.. date: 2020-05-24-02-42-26
.. nonce: ZmO9Ev
.. section: Core and Builtins

Support the "-d" debug flag in the new PEG parser. Patch by Pablo Galindo

..

.. bpo: 40217
.. date: 2020-05-23-01-15-51
.. nonce: jZsHTc
.. section: Core and Builtins

Instances of types created with :c:func:`PyType_FromSpecWithBases` will no
longer automatically visit their class object when traversing references in
the garbage collector. The user is expected to manually visit the object's
class. Patch by Pablo Galindo.

..

.. bpo: 40696
.. date: 2020-05-21-01-54-00
.. nonce: u3n8Wx
.. section: Core and Builtins

Fix a hang that can arise after :meth:`generator.throw` due to a cycle in
the exception context chain.

..

.. bpo: 39791
.. date: 2020-06-05-19-29-10
.. nonce: _CcO3d
.. section: Library

Refresh importlib.metadata from importlib_metadata 1.6.1.

..

.. bpo: 40807
.. date: 2020-06-04-16-25-15
.. nonce: yYyLWx
.. section: Library

Stop codeop._maybe_compile, used by code.InteractiveInterpreter (and IDLE).
from from emitting each warning three times.

..

.. bpo: 39791
.. date: 2020-06-02-02-16-02
.. nonce: StCJlA
.. section: Library

Built-in loaders (SourceFileLoader and ZipImporter) now supply
``TraversableResources`` implementations for ``ResourceReader``, and the
fallback function has been removed.

..

.. bpo: 17005
.. date: 2020-05-31-23-32-36
.. nonce: JlRUGB
.. section: Library

The topological sort functionality that was introduced initially in the
:mod:`functools` module has been moved to a new :mod:`graphlib` module to
better accommodate the new tools and keep the original scope of the
:mod:`functools` module. Patch by Pablo Galindo

..

.. bpo: 40777
.. date: 2020-05-28-17-32-29
.. nonce: 1kJU6N
.. section: Library

Initialize PyDateTime_IsoCalendarDateType.tp_base at run-time to avoid
errors on some compilers.

..

.. bpo: 40767
.. date: 2020-05-27-21-27-01
.. nonce: L5MnVV
.. section: Library

:mod:`webbrowser` now properly finds the default browser in pure Wayland
systems by checking the WAYLAND_DISPLAY environment variable. Patch
contributed by Jérémy Attali.

..

.. bpo: 40791
.. date: 2020-05-27-18-04-52
.. nonce: IzpNor
.. section: Library

:func:`hashlib.compare_digest` uses OpenSSL's ``CRYPTO_memcmp()`` function
when OpenSSL is available.

..

.. bpo: 40795
.. date: 2020-05-27-17-00-18
.. nonce: eZSnHA
.. section: Library

:mod:`ctypes` module: If ctypes fails to convert the result of a callback or
if a ctypes callback function raises an exception, sys.unraisablehook is now
called with an exception set. Previously, the error was logged into stderr
by :c:func:`PyErr_Print`.

..

.. bpo: 30008
.. date: 2020-05-25-22-18-38
.. nonce: CKC3td
.. section: Library

Fix :mod:`ssl` code to be compatible with OpenSSL 1.1.x builds that use
``no-deprecated`` and ``--api=1.1.0``.

..

.. bpo: 30064
.. date: 2020-05-25-11-52-23
.. nonce: 6CICsH
.. section: Library

Fix asyncio ``loop.sock_*`` race condition issue

..

.. bpo: 40759
.. date: 2020-05-24-23-52-35
.. nonce: DdZdaw
.. section: Library

Deprecate the :mod:`symbol` module.

..

.. bpo: 40737
.. date: 2020-05-23-00-22-11
.. nonce: iph-CM
.. section: Library

Fix possible reference leak for :mod:`sqlite3` initialization.

..

.. bpo: 40698
.. date: 2020-05-20-14-38-04
.. nonce: zwl5Hc
.. section: Library

:mod:`distutils` upload creates SHA2-256 and Blake2b-256 digests. MD5
digests is skipped if platform blocks MD5.

..

.. bpo: 40695
.. date: 2020-05-20-13-03-28
.. nonce: lr4aIS
.. section: Library

:mod:`hashlib` no longer falls back to builtin hash implementations when
OpenSSL provides a hash digest and the algorithm is blocked by security
policy.

..

.. bpo: 9216
.. date: 2020-05-20-12-53-20
.. nonce: ps7Yf1
.. section: Library

func:`hashlib.new` passed ``usedforsecurity`` to OpenSSL EVP constructor
``_hashlib.new()``. test_hashlib and test_smtplib handle strict security
policy better.

..

.. bpo: 40614
.. date: 2020-05-18-22-41-02
.. nonce: 8j3kmq
.. section: Library

:func:`ast.parse` will not parse self documenting expressions in f-strings
when passed ``feature_version`` is less than ``(3, 8)``.

..

.. bpo: 40671
.. date: 2020-05-18-15-26-31
.. nonce: NeZ9Cy
.. section: Library

Prepare ``_hashlib`` for :pep:`489` and use :c:func:`PyModule_AddType`.

..

.. bpo: 32309
.. date: 2020-05-17-02-03-09
.. nonce: KM9psl
.. section: Library

Added a new :term:`coroutine` :func:`asyncio.to_thread`. It is mainly used
for running IO-bound functions in a separate thread to avoid blocking the
event loop, and essentially works as a high-level version of
:meth:`~asyncio.loop.run_in_executor` that can directly take keyword
arguments.

..

.. bpo: 40630
.. date: 2020-05-15-13-40-15
.. nonce: YXEX_M
.. section: Library

Added :func:`tracemalloc.reset_peak` to set the peak size of traced memory
blocks to the current size, to measure the peak of specific pieces of code.

..

.. bpo: 13097
.. date: 2020-05-06-02-01-25
.. nonce: Wh5xSK
.. section: Library

``ctypes`` now raises an ``ArgumentError`` when a callback is invoked with
more than 1024 arguments.

..

.. bpo: 23082
.. date: 2020-04-20-22-08-36
.. nonce: iX90Id
.. section: Library

Updated the error message and docs of PurePath.relative_to() to better
reflect the function behaviour.

..

.. bpo: 39244
.. date: 2020-02-23-15-09-47
.. nonce: aBK5IM
.. section: Library

Fixed :class:`multiprocessing.context.get_all_start_methods` to properly
return the default method first on macOS.

..

.. bpo: 39040
.. date: 2019-12-15-18-47-20
.. nonce: tKa0Qs
.. section: Library

Fix parsing of invalid mime headers parameters by collapsing whitespace
between encoded words in a bare-quote-string.

..

.. bpo: 35714
.. date: 2019-10-25-23-45-49
.. nonce: fw3xb7
.. section: Library

:exc:`struct.error` is now raised if there is a null character in a
:mod:`struct` format string.

..

.. bpo: 36290
.. date: 2019-03-17-19-01-53
.. nonce: 7VXo_K
.. section: Library

AST nodes are now raising :exc:`TypeError` on conflicting keyword arguments.
Patch contributed by Rémi Lapeyre.

..

.. bpo: 17258
.. date: 2020-05-26-07-53-31
.. nonce: X_IKTQ
.. section: Tests

Skip some :mod:`multiprocessing` tests when MD5 hash digest is blocked.

..

.. bpo: 40514
.. date: 2020-05-19-17-43-38
.. nonce: gW-66U
.. section: Build

Remove ``--with-experimental-isolated-subinterpreters`` configure option in
Python 3.9: the experiment continues in the master branch, but it's no
longer needed in 3.9.

..

.. bpo: 40683
.. date: 2020-05-19-10-54-08
.. nonce: W8JHrr
.. section: Build

Fixed an issue where the :mod:`zoneinfo` module and its tests were not
included when Python is installed with ``make``.

..

.. bpo: 39631
.. date: 2020-05-19-14-43-33
.. nonce: Z5yXam
.. section: Windows

Changes the registered MIME type for ``.py`` files on Windows to
``text/x-python`` instead of ``text/plain``.

..

.. bpo: 40677
.. date: 2020-05-19-04-11-12
.. nonce: qQbLW8
.. section: Windows

Manually define IO_REPARSE_TAG_APPEXECLINK in case some old Windows SDK
doesn't have it.

..

.. bpo: 40741
.. date: 2020-06-07-20-10-56
.. nonce: 80A2BW
.. section: macOS

Update macOS installer to use SQLite 3.32.2.

..

.. bpo: 39885
.. date: 2020-05-29-18-21-58
.. nonce: zB_-bN
.. section: IDLE

Make context menu Cut and Copy work again when right-clicking within a
selection.

..

.. bpo: 40723
.. date: 2020-05-24-06-19-43
.. nonce: AJLd4U
.. section: IDLE

Make test_idle pass when run after import.

..

.. bpo: 40910
.. date: 2020-06-08-15-59-06
.. nonce: L56oI0
.. section: C API

Export explicitly the :c:func:`Py_GetArgcArgv` function to the C API and
document the function. Previously, it was exported implicitly which no
longer works since Python is built with ``-fvisibility=hidden``.

..

.. bpo: 40724
.. date: 2020-06-04-08-01-23
.. nonce: qIIdSi
.. section: C API

Allow defining buffer slots in type specs.

..

.. bpo: 40826
.. date: 2020-06-01-16-12-37
.. nonce: zQzFoK
.. section: C API

:c:func:`PyOS_InterruptOccurred` now fails with a fatal error if it is
called with the GIL released.