attrs_strict documentation
============================

Background
----------

The purpose of the library is to provide runtime validation for attributes specified in
`attrs <https://www.attrs.org/en/stable/>`_ data classes. The types supported are all the builtin
types and most of the ones defined in the typing library. For Python 2, the typing module is
available through the backport found `here <https://pypi.org/project/typing/>`_.

Getting started
---------------

Run :code:`pip install attrs-strict` to install the latest stable version from PyPi.
The source code is hosted on github at `<https://github.com/bloomberg/attrs-strict>`_.
The library currently supports :code:`Python2.7`, :code:`Python3.6` and :code:`Python3.7`.

Usage and examples
------------------
Type enforcement is based on the :code:`type` attribute set on any field specified in an :code:`attrs` dataclass.
If the type argument is not specified no validation takes place.

.. code-block:: python

  from typing import List

  import attr

  from attrs_strict import type_validator, ContainerError

  >>> @attr.s
  ... class SomeClass(object):
  ...     list_of_numbers = attr.ib(
  ...         validator=type_validator(),
  ...         type=List[int]
  ...     )
  ...

  >>> sc = SomeClass([1,2,3,4])
  >>> sc
  SomeClass(list_of_numbers=[1, 2, 3, 4])

  >>> SomeClass([1,2,3,'four'])
  attrs_strict._error.AttributeTypeError(
    "list_of_numbers must be typing.List[int]"
    "(got four that is a <class 'str'>) in [1, 2, 3, 'four']"
  )

Nested type exceptions are validated acordingly, and a backtrace to the initial
container is maintained to ease with debugging. This means that if an exception
occurs because a nested element doesn't have the correct type, the representation
of the exception will contain the path to the specific element that caused the exception.

.. code-block:: python

  from typing import List, Tuple

  import attr

  from attrs_strict import type_validator, ContainerError

  >>> @attr.s
  ... class SomeClass(object):
  ...     names = attr.ib(
  ...        validator=type_validator(), type=List[Tuple[str, str]]
  ...     )

  >>> sc = SomeClass(names=[('Moo', 'Moo'), ('Zoo',123)])
  attrs_strict._error.AttributeTypeError(
    "names must be"
    "typing.List[typing.Tuple[str, str]] (got 123 that is a <class 'int'>) in"
    "('Zoo', 123) in [('Moo', 'Moo'), ('Zoo', 123)]"
  )

What is currently supported ?
-----------------------------

Currently there's support for builtin types and types specified in the :code:`typing`
module: :code:`List`, :code:`Dict`, :code:`DefaultDict`, :code:`Set`, :code:`Union`,
:code:`Tuple` and any combination of them. This means that you can specify nested
types like  :code:`List[List[Dict[int, str]]]` and the validation would check if
attribute has the specific type.

:code:`Callables`, :code:`TypeVars` or :code:`Generics` are not supported yet but
there are plans to support this in the future.

.. toctree::
   :maxdepth: 1

   api