Anyio

- Added the ``maybe_async()`` and ``maybe_async_cm()`` functions to facilitate forward
compatibility with AnyIO 3
- Fixed socket stream bug on asyncio where receiving a half-close from the peer would
shut down the entire connection
- Fixed native task names not being set on asyncio on Python 3.8+
- Fixed ``TLSStream.send_eof()`` raising ``ValueError`` instead of the expected
``NotImplementedError``
- Fixed ``open_signal_receiver()`` on asyncio and curio hanging if the cancel scope was
cancelled before the function could run
- Fixed Trio test runner causing unwarranted test errors on ``BaseException``
(PR by Matthias Urlichs)
- Fixed formatted output of ``ExceptionGroup`` containing too many newlines

- Added the ``spawn_task()`` and ``wrap_async_context_manager()`` methods to
``BlockingPortal``
- Added the ``handshake_timeout`` and ``error_handler`` parameters to ``TLSListener``
- Fixed ``Event`` objects on the trio backend not inheriting from ``anyio.abc.Event``
- Fixed ``run_sync_in_worker_thread()`` raising ``UnboundLocalError`` on asyncio when
cancelled
- Fixed ``send()`` on socket streams not raising any exception on asyncio, and an
unwrapped ``BrokenPipeError`` on trio and curio when the peer has disconnected
- Fixed ``MemoryObjectSendStream.send()`` raising ``BrokenResourceError`` when the last
receiver is closed right after receiving the item
- Fixed ``ValueError: Invalid file descriptor: -1`` when closing a ``SocketListener`` on
asyncio

- Fixed one more case of
``AttributeError: 'async_generator_asend' object has no attribute 'cr_await'`` on
asyncio

- Fixed broken ``MultiListener.extra()`` (PR by daa)
- Fixed ``TLSStream`` returning an empty bytes object instead of raising ``EndOfStream``
when trying to receive from the stream after a closing handshake
- Fixed ``AttributeError`` when cancelling a task group's scope inside an async test
fixture on asyncio
- Fixed ``wait_all_tasks_blocked()`` raising ``AttributeError`` on asyncio if a native
task is waiting on an async generator's ``asend()`` method

- General new features:

- Added support for subprocesses
- Added support for "blocking portals" which allow running functions in the event loop
thread from external threads
- Added the ``anyio.aclose_forcefully()`` function for closing asynchronous resources
as quickly as possible

- General changes/fixes:

- **BACKWARDS INCOMPATIBLE** Some functions have been renamed or removed (see further
below for socket/fileio API changes):

- ``finalize()`` → (removed; use ``contextlib.aclosing()`` instead)
- ``receive_signals()`` → ``open_signal_receiver()``
- ``run_in_thread()`` → ``run_sync_in_worker_thread()``
- ``current_default_thread_limiter()`` → ``current_default_worker_thread_limiter()``
- ``ResourceBusyError`` → ``BusyResourceError``
- **BACKWARDS INCOMPATIBLE** Exception classes were moved to the top level package
- Dropped support for Python 3.5
- Bumped minimum versions of trio and curio to v0.16 and v1.4, respectively
- Changed the ``repr()`` of ``ExceptionGroup`` to match trio's ``MultiError``

- Backend specific changes and fixes:

- ``asyncio``: Added support for ``ProactorEventLoop``. This allows asyncio
applications to use AnyIO on Windows even without using AnyIO as the entry point.
- ``asyncio``: The asyncio backend now uses ``asyncio.run()`` behind the scenes which
properly shuts down async generators and cancels any leftover native tasks
- ``curio``: Worked around the limitation where a task can only be cancelled twice
(any cancellations beyond that were ignored)
- ``asyncio`` + ``curio``: a cancellation check now calls ``sleep(0)``, allowing the
scheduler to switch to a different task
- ``asyncio`` + ``curio``: Host name resolution now uses `IDNA 2008`_ (with UTS 46
compatibility mapping, just like trio)
- ``asyncio`` + ``curio``: Fixed a bug where a task group would abandon its subtasks
if its own cancel scope was cancelled while it was waiting for subtasks to finish
- ``asyncio`` + ``curio``: Fixed recursive tracebacks when a single exception from an
inner task group is reraised in an outer task group

- Socket/stream changes:

- **BACKWARDS INCOMPATIBLE** The stream class structure was completely overhauled.
There are now separate abstract base classes for receive and send streams, byte
streams and reliable and unreliable object streams. Stream wrappers are much better
supported by this new ABC structure and a new "typed extra attribute" system that
lets you query the wrapper chain for the attributes you want via ``.extra(...)``.
- **BACKWARDS INCOMPATIBLE** Socket server functionality has been refactored into a
network-agnostic listener system
- **BACKWARDS INCOMPATIBLE** TLS functionality has been split off from
``SocketStream`` and can now work over any bidirectional bytes-based stream – you
can now establish a TLS encrypted communications pathway over UNIX sockets or even
memory object streams. The ``TLSRequired`` exception has also been removed as it is
no longer necessary.
- **BACKWARDS INCOMPATIBLE** Buffering functionality (``receive_until()`` and
``receive_exactly()``) was split off from ``SocketStream`` into a stream wrapper
class (``anyio.streams.buffered.BufferedByteReceiveStream``)
- **BACKWARDS INCOMPATIBLE** IPv6 addresses are now reported as 2-tuples. If original
4-tuple form contains a nonzero scope ID, it is appended to the address with ``%``
as the separator.
- **BACKWARDS INCOMPATIBLE** Byte streams (including socket streams) now raise
``EndOfStream`` instead of returning an empty bytes object when the stream has been
closed from the other end
- **BACKWARDS INCOMPATIBLE** The socket API has changes:

- ``create_tcp_server()`` → ``create_tcp_listener()``
- ``create_unix_server()`` → ``create_unix_listener()``
- ``create_udp_socket()`` had some of its parameters changed:

- ``interface`` → ``local_address``
- ``port`` → ``local_port``
- ``reuse_address`` was replaced with ``reuse_port`` (and sets ``SO_REUSEPORT``
instead of ``SO_REUSEADDR``)
- ``connect_tcp()`` had some of its parameters changed:

- ``address`` → ``remote_address``
- ``port`` → ``remote_port``
- ``bind_host`` → ``local_address``
- ``bind_port`` → (removed)
- ``autostart_tls`` → ``tls``
- ``tls_hostname`` (new parameter, when you want to match the certificate against
against something else than ``remote_address``)
- ``connect_tcp()`` now returns a ``TLSStream`` if TLS was enabled
- ``notify_socket_closing()`` was removed, as it is no longer used by AnyIO
- ``SocketStream`` has changes to its methods and attributes:

- ``address`` → ``.extra(SocketAttribute.local_address)``
- ``alpn_protocol`` → ``.extra(TLSAttribute.alpn_protocol)``
- ``close()`` → ``aclose()``
- ``get_channel_binding`` → ``.extra(TLSAttribute.channel_binding_tls_unique)``
- ``cipher`` → ``.extra(TLSAttribute.cipher)``
- ``getpeercert`` → ``.extra(SocketAttribute.peer_certificate)`` or
``.extra(SocketAttribute.peer_certificate_binary)``
- ``getsockopt()`` → ``.extra(SocketAttribute.raw_socket).getsockopt(...)``
- ``peer_address`` → ``.extra(SocketAttribute.remote_address)``
- ``receive_chunks()`` → (removed; use ``async for`` on the stream instead)
- ``receive_delimited_chunks()`` → (removed)
- ``receive_exactly()`` → ``BufferedReceiveStream.receive_exactly()``
- ``receive_some()`` → ``receive()``
- ``receive_until()`` → ``BufferedReceiveStream.receive_until()``
- ``send_all()`` → ``send()``
- ``setsockopt()`` → ``.extra(SocketAttribute.raw_socket).setsockopt(...)``
- ``shared_ciphers`` → ``.extra(TLSAttribute.shared_ciphers)``
- ``server_side`` → ``.extra(TLSAttribute.server_side)``
- ``start_tls()`` → ``stream = TLSStream.wrap(...)``
- ``tls_version`` → ``.extra(TLSAttribute.tls_version)``
- ``UDPSocket`` has changes to its methods and attributes:

- ``address`` → ``.extra(SocketAttribute.local_address)``
- ``getsockopt()`` → ``.extra(SocketAttribute.raw_socket).getsockopt(...)``
- ``port`` → ``.extra(SocketAttribute.local_port)``
- ``receive()`` no longer takes a maximum bytes argument
- ``receive_packets()`` → (removed; use ``async for`` on the UDP socket instead)
- ``send()`` → requires a tuple for destination now (address, port), for
compatibility with the new ``UnreliableObjectStream`` interface. The
``sendto()`` method works like the old ``send()`` method.
- ``setsockopt()`` → ``.extra(SocketAttribute.raw_socket).setsockopt(...)``
- **BACKWARDS INCOMPATIBLE** Renamed the ``max_size`` parameter to ``max_bytes``
wherever it occurred (this was inconsistently named ``max_bytes`` in some subclasses
before)
- Added memory object streams as a replacement for queues
- Added stream wrappers for encoding/decoding unicode strings
- Support for the ``SO_REUSEPORT`` option (allows binding more than one socket to the
same address/port combination, as long as they all have this option set) has been
added to TCP listeners and UDP sockets
- The ``send_eof()`` method was added to all (bidirectional) streams

- File I/O changes:

- **BACKWARDS INCOMPATIBLE** Asynchronous file I/O functionality now uses a common
code base (``anyio.AsyncFile``) instead of backend-native classes
- **BACKWARDS INCOMPATIBLE** The File I/O API has changes to its functions and
methods:

- ``aopen()`` → ``open_file()``
- ``AsyncFileclose()`` → ``AsyncFileaclose()``

- Task synchronization changes:

- **BACKWARDS INCOMPATIBLE** Queues were replaced by memory object streams
- **BACKWARDS INCOMPATIBLE** Added the ``acquire()`` and ``release()`` methods to the
``Lock``, ``Condition`` and ``Semaphore`` classes
- **BACKWARDS INCOMPATIBLE** Removed the ``Event.clear()`` method. You must now
replace the event object with a new one rather than clear the old one.
- Fixed ``Condition.wait()`` not working on asyncio and curio (PR by Matt Westcott)

- Testing changes:

- **BACKWARDS INCOMPATIBLE** Removed the ``--anyio-backends`` command line option for
the pytest plugin. Use the ``-k`` option to do ad-hoc filtering, and the
``anyio_backend`` fixture to control which backends you wish to run the tests by
default.
- The pytest plugin was refactored to run the test and all its related async fixtures
inside the same event loop, making async fixtures much more useful
- Fixed Hypothesis support in the pytest plugin (it was not actually running the
Hypothesis tests at all)

.. _IDNA 2008: https://tools.ietf.org/html/rfc5895

- Added async name resolution functions (``anyio.getaddrinfo()`` and
``anyio.getnameinfo()``)
- Added the ``family`` and ``reuse_address`` parameters to ``anyio.create_udp_socket()``
(Enables multicast support; test contributed by Matthias Urlichs)
- Fixed ``fail.after(0)`` not raising a timeout error on asyncio and curio
- Fixed ``move_on_after()`` and ``fail_after()`` getting stuck on curio in some
circumstances
- Fixed socket operations not allowing timeouts to cancel the task
- Fixed API documentation on ``Stream.receive_until()`` which claimed that the delimiter
will be included in the returned data when it really isn't
- Harmonized the default task names across all backends
- ``wait_all_tasks_blocked()`` no longer considers tasks waiting on ``sleep(0)`` to be
blocked on asyncio and curio
- Fixed the type of the ``address`` parameter in ``UDPSocket.send()`` to include
``IPAddress`` objects (which were already supported by the backing implementation)
- Fixed ``UDPSocket.send()`` to resolve host names using ``anyio.getaddrinfo()`` before
calling ``socket.sendto()`` to avoid blocking on synchronous name resolution
- Switched to using ``anyio.getaddrinfo()`` for name lookups