Bump attrs from 19.3.0 to 20.1.0

[dependabot-preview]

Bumps attrs from 19.3.0 to 20.1.0.

Release notes

Sourced from attrs's releases.

20.1.0

Backward-incompatible Changes

• Python 3.4 is not supported anymore. It has been unsupported by the Python core team for a while now, its PyPI downloads are negligible, and our CI provider removed it as a supported option.

  It's very unlikely that attrs will break under 3.4 anytime soon, which is why we do not block its installation on Python 3.4. But we don't test it anymore and will block it once someone reports breakage. #608

Deprecations

• Less of a deprecation and more of a heads up: the next release of attrs will introduce an attrs namespace. That means that you'll finally be able to run import attrs with new functions that aren't cute abbreviations and that will carry better defaults.

  This should not break any of your code, because project-local packages have priority before installed ones. If this is a problem for you for some reason, please report it to our bug tracker and we'll figure something out.

  The old attr namespace isn't going anywhere and its defaults are not changing -- this is a purely additive measure. Please check out the linked issue for more details.

  These new APIs have been added provisionally as part of #666 so you can try them out today and provide feedback. Learn more in the API docs. #408

Changes

• Added attr.resolve_types(). It ensures that all forward-references and types in string form are resolved into concrete types.

  You need this only if you need concrete types at runtime. That means that if you only use types for static type checking, you do not need this function. #288, #302

• Added @attr.s(collect_by_mro=False) argument that if set to True fixes the collection of attributes from base classes.

  It's only necessary for certain cases of multiple-inheritance but is kept off for now for backward-compatibility reasons. It will be turned on by default in the future.

  As a side-effect, attr.Attribute now always has an inherited attribute indicating whether an attribute on a class was directly defined or inherited. #428, #635

• On Python 3, all generated methods now have a docstring explaining that they have been created by attrs. #506

• It is now possible to prevent attrs from auto-generating the __setstate__ and __getstate__ methods that are required for pickling of slotted classes.

  Either pass @attr.s(getstate_setstate=False) or pass @attr.s(auto_detect=True) and implement them yourself: if attrs finds either of the two methods directly on the decorated class, it assumes implicitly getstate_setstate=False (and implements neither).

  This option works with dict classes but should never be necessary. #512, #513, #642

• Fixed a ValueError: Cell is empty bug that could happen in some rare edge cases. #590

• attrs can now automatically detect your own implementations and infer init=False, repr=False, eq=False, order=False, and hash=False if you set @attr.s(auto_detect=True). attrs will ignore inherited methods. If the argument implies more than one method (e.g. eq=True creates both __eq__ and __ne__), it's enough for one of them to exist and attrs will create neither.

  This feature requires Python 3. #607

• Added attr.converters.pipe(). The feature allows combining multiple conversion callbacks into one by piping the value through all of them, and retuning the last result.

  As part of this feature, we had to relax the type information for converter callables. #618

Changelog

Sourced from attrs's changelog.

20.1.0 (2020-08-20)

Backward-incompatible Changes

• Python 3.4 is not supported anymore. It has been unsupported by the Python core team for a while now, its PyPI downloads are negligible, and our CI provider removed it as a supported option.

  It's very unlikely that attrs will break under 3.4 anytime soon, which is why we do not block its installation on Python 3.4. But we don't test it anymore and will block it once someone reports breakage. #608

Deprecations

• Less of a deprecation and more of a heads up: the next release of attrs will introduce an attrs namespace. That means that you'll finally be able to run import attrs with new functions that aren't cute abbreviations and that will carry better defaults.

  This should not break any of your code, because project-local packages have priority before installed ones. If this is a problem for you for some reason, please report it to our bug tracker and we'll figure something out.

  The old attr namespace isn't going anywhere and its defaults are not changing – this is a purely additive measure. Please check out the linked issue for more details.

  These new APIs have been added provisionally as part of #666 so you can try them out today and provide feedback. Learn more in the API docs. #408

Changes

• Added attr.resolve_types(). It ensures that all forward-references and types in string form are resolved into concrete types.

  You need this only if you need concrete types at runtime. That means that if you only use types for static type checking, you do not need this function. #288, #302

• Added @attr.s(collect_by_mro=False) argument that if set to True fixes the collection of attributes from base classes.

  It's only necessary for certain cases of multiple-inheritance but is kept off for now for backward-compatibility reasons. It will be turned on by default in the future.

  As a side-effect, attr.Attribute now always has an inherited attribute indicating whether an attribute on a class was directly defined or inherited. #428, #635

• On Python 3, all generated methods now have a docstring explaining that they have been created by attrs. #506

• It is now possible to prevent attrs from auto-generating the __setstate__ and __getstate__ methods that are required for pickling of slotted classes.

  Either pass @attr.s(getstate_setstate=False) or pass @attr.s(auto_detect=True) and implement them yourself: if attrs finds either of the two methods directly on the decorated class, it assumes implicitly getstate_setstate=False (and implements neither).

  This option works with dict classes but should never be necessary. #512, #513, #642

• Fixed a ValueError: Cell is empty bug that could happen in some rare edge cases. #590

• attrs can now automatically detect your own implementations and infer init=False, repr=False, eq=False, order=False, and hash=False if you set @attr.s(auto_detect=True). attrs will ignore inherited methods. If the argument implies more than one method (e.g. eq=True creates both __eq__ and __ne__), it's enough for one of them to exist and attrs will create neither.

  This feature requires Python 3. #607

• Added attr.converters.pipe(). The feature allows combining multiple conversion callbacks into one by piping the value through all of them, and retuning the last result.

  As part of this feature, we had to relax the type information for converter callables. #618

• Fixed serialization behavior of non-slots classes with cache_hash=True. The hash cache will be cleared on operations which make "deep copies" of instances of classes with hash caching, though the cache will not be cleared with shallow copies like those made by copy.copy().

  Previously, copy.deepcopy() or serialization and deserialization with pickle would result in an un-initialized object.

  This change also allows the creation of cache_hash=True classes with a custom __setstate__, which was previously forbidden (#494). #620

Commits

• 90386b6 Prepare 20.1.0
• d523371 Prevent reST getting upset by multiple links to #666
• fda437c Add attr.field (#669)
• c67a649 Explain that slotted classes don't support multiple inheritance
• b02335f Add attr.define/mutable/frozen (#666)
• 131d147 Fix doc
• aea6d6f Announce import attrs
• d59b154 Clean up api docs a bit
• d4150f2 Run CI against 3.9 pre-release (#664)
• 106c33c Clear setattr if it was inherited && written by us (#663)
• Additional commits viewable in compare view

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