v23.2.0

23.2.0 (2023-11-17)

Welcome to cattrs 23.2.0! Thanks to all our wonderful contributors, this release happens to have the largest changelog so far.

Here are some of the noteworthy additions, see below for the entire changelog.

More Powerful Unions in preconf

Courtesy of the union passthrough strategy, the following class (and others like it, this is just a complex example) will work out-of-the-box on any preconf converter:

@define
class MyClass:
    my_field: str | Literal[1] | MyOtherClass

The strategy has been preapplied to all preconf converters, but it can be manually applied to any converter.

Default Disambiguation via Literals

When structuring a union of attrs classes, cattrs will default to the default union strategy.

This strategy works by finding required unique fields in the given classes.
It has been enhanced with support for matching on fields annotated as Literals.

from typing import Literal

@define
class ClassA:
    field_one: Literal["one"]

@define
class ClassB:
    field_one: Literal["two"] = "two"

Un/structuring Hooks on Classes

cattrs defaults to having un/structuring hooks separate from the models.
With the use class methods strategy, you are free to defy this design decision and configure a converter to look for hooks on the models themselves.

The Complete Changelog

• Potentially breaking: skip attrs fields marked as init=False by default. This change is potentially breaking for unstructuring.
  See here for instructions on how to restore the old behavior.
  (#40 #395)
• Potentially breaking: cattrs.gen.make_dict_structure_fn and cattrs.gen.typeddicts.make_dict_structure_fn will use the values for the detailed_validation and forbid_extra_keys parameters from the given converter by default now.
  If you're using these functions directly, the old behavior can be restored by passing in the desired values directly.
  (#410 #411)
• Potentially breaking: The default union structuring strategy will also use fields annotated as typing.Literal to help guide structuring.
  See here for instructions on how to restore the old behavior.
  (#391)
• Python 3.12 is now supported. Python 3.7 is no longer supported; use older releases there.
  (#424)
• Implement the union passthrough strategy, enabling much richer union handling for preconfigured converters. Learn more here.
• Introduce the use_class_methods strategy. Learn more here.
  (#405)
• The omit parameter of cattrs.override is now of type bool | None (from bool).
  None is the new default and means to apply default cattrs handling to the attribute, which is to omit the attribute if it's marked as init=False, and keep it otherwise.
• Converters can now be initialized with custom fallback hook factories for un/structuring.
  (#331 #441)
• Add support for date to preconfigured converters.
  (#420)
• Add support for datetime.dates to the PyYAML preconfigured converter.
  (#393)
• Fix format_exception() parameter working for recursive calls to transform_error().
  (#389)
• attrs aliases are now supported, although aliased fields still map to their attribute name instead of their alias by default when un/structuring.
  (#322 #391)
• Fix TypedDicts with periods in their field names.
  (#376 #377)
• Optimize and improve unstructuring of Optional (unions of one type and None).
  (#380 #381)
• Fix format_exception and transform_error type annotations.
• Improve the implementation of cattrs._compat.is_typeddict. The implementation is now simpler, and relies on fewer private implementation details from typing and typing_extensions.
  (#384)
• Improve handling of TypedDicts with forward references.
• Speed up generated attrs and TypedDict structuring functions by changing their signature slightly.
  (#388)
• Fix copying of converters with function hooks.
  (#398 #399)
• Broaden cattrs.preconf.orjson.OrjsonConverter.loads type definition for the preconf orjson converter.
  (#400)
• AttributeValidationNote and IterableValidationNote are now picklable.
  (#408)
• Fix structuring Final lists.
  (#412)
• Fix certain cases of structuring Annotated types.
  (#418)
• Fix the tagged union strategy to work with forbid_extra_keys.
  (#402 #443)
• Use PDM instead of Poetry.
• cattrs is now linted with Ruff.
• Remove some unused lines in the unstructuring code.
  (#416)
• Fix handling classes inheriting from non-generic protocols.
  (#374 #436)
• The documentation Makefile now supports the htmlview and htmllive targets. (#442)
• cattrs is now published using PyPI Trusted Publishers, and main branch commits are automatically deployed to Test PyPI.