Update attrs to 21.4.0

[pyup-bot]

This PR updates attrs from 21.2.0 to 21.4.0.

Changelog

21.4.0

-------------------

Changes
^^^^^^^

- Fixed the test suite on PyPy3.8 where ``cloudpickle`` does not work.
`892 <https://github.com/python-attrs/attrs/issues/892>`_
- Fixed ``coverage report`` for projects that use ``attrs`` and don't set a ``--source``.
`895 <https://github.com/python-attrs/attrs/issues/895>`_,
`896 <https://github.com/python-attrs/attrs/issues/896>`_


----

21.3.0

-------------------

Backward-incompatible Changes
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

- When using ``define``, converters are now run by default when setting an attribute on an instance -- additionally to validators.
I.e. the new default is ``on_setattr=[attrs.setters.convert, attrs.setters.validate]``.

This is unfortunately a breaking change, but it was an oversight, impossible to raise a ``DeprecationWarning`` about, and it's better to fix it now while the APIs are very fresh with few users.
`835 <https://github.com/python-attrs/attrs/issues/835>`_,
`886 <https://github.com/python-attrs/attrs/issues/886>`_
- ``import attrs`` has finally landed!
As of this release, you can finally import ``attrs`` using its proper name.

Not all names from the ``attr`` namespace have been transferred; most notably ``attr.s`` and ``attr.ib`` are missing.
See ``attrs.define`` and ``attrs.field`` if you haven't seen our next-generation APIs yet.
A more elaborate explanation can be found `On The Core API Names <https://www.attrs.org/en/latest/names.html>`_

This feature is at least for one release **provisional**.
We don't *plan* on changing anything, but such a big change is unlikely to go perfectly on the first strike.

The API docs have been mostly updated, but it will be an ongoing effort to change everything to the new APIs.
Please note that we have **not** moved -- or even removed -- anything from ``attr``!

Please do report any bugs or documentation inconsistencies!
`887 <https://github.com/python-attrs/attrs/issues/887>`_


Changes
^^^^^^^

- ``attr.asdict(retain_collection_types=False)`` (default) dumps collection-esque keys as tuples.
`646 <https://github.com/python-attrs/attrs/issues/646>`_,
`888 <https://github.com/python-attrs/attrs/issues/888>`_
- ``__match_args__`` are now generated to support Python 3.10's
`Structural Pattern Matching <https://docs.python.org/3.10/whatsnew/3.10.html#pep-634-structural-pattern-matching>`_.
This can be controlled by the ``match_args`` argument to the class decorators on Python 3.10 and later.
On older versions, it is never added and the argument is ignored.
`815 <https://github.com/python-attrs/attrs/issues/815>`_
- If the class-level *on_setattr* is set to ``attrs.setters.validate`` (default in ``define`` and ``mutable``) but no field defines a validator, pretend that it's not set.
`817 <https://github.com/python-attrs/attrs/issues/817>`_
- The generated ``__repr__`` is significantly faster on Pythons with f-strings.
`819 <https://github.com/python-attrs/attrs/issues/819>`_
- Attributes transformed via ``field_transformer`` are wrapped with ``AttrsClass`` again.
`824 <https://github.com/python-attrs/attrs/issues/824>`_
- Generated source code is now cached more efficiently for identical classes.
`828 <https://github.com/python-attrs/attrs/issues/828>`_
- Added ``attrs.converters.to_bool()``.
`830 <https://github.com/python-attrs/attrs/issues/830>`_
- ``attrs.resolve_types()`` now resolves types of subclasses after the parents are resolved.
`842 <https://github.com/python-attrs/attrs/issues/842>`_
`843 <https://github.com/python-attrs/attrs/issues/843>`_
- Added new validators: ``lt(val)`` (< val), ``le(va)`` (≤ val), ``ge(val)`` (≥ val), ``gt(val)`` (> val), and ``maxlen(n)``.
`845 <https://github.com/python-attrs/attrs/issues/845>`_
- ``attrs`` classes are now fully compatible with `cloudpickle <https://github.com/cloudpipe/cloudpickle>`_ (no need to disable ``repr`` anymore).
`857 <https://github.com/python-attrs/attrs/issues/857>`_
- Added new context manager ``attrs.validators.disabled()`` and functions ``attrs.validators.(set|get)_disabled()``.
They deprecate ``attrs.(set|get)_run_validators()``.
All functions are interoperable and modify the same internal state.
They are not – and never were – thread-safe, though.
`859 <https://github.com/python-attrs/attrs/issues/859>`_
- ``attrs.validators.matches_re()`` now accepts pre-compiled regular expressions in addition to pattern strings.
`877 <https://github.com/python-attrs/attrs/issues/877>`_


----

Links

• PyPI: https://pypi.org/project/attrs
• Changelog: https://pyup.io/changelogs/attrs/
• Homepage: https://www.attrs.org/