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Description:

attrsstrict 1.0.1

attrs runtime validation
attrs-strict is a Python package which contains runtime validation for
attrs data classes based on the types existing in the typing module.
Rationale
The purpose of the library is to provide runtime validation for attributes specified in
attrs 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.
Quick Start
Type enforcement is based on the type attribute set on any field specified in an attrs dataclass. If the type
argument is not specified, no validation takes place.
pip install attrs-strict
from typing import List
import attr
from attrs_strict import type_validator

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

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

try:
SomeClass([1, 2, 3, "four"])
except ValueError as exception:
print(repr(exception))

SomeClass(list_of_numbers=[1, 2, 3, 4])
<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 accordingly, 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.
from typing import List, Tuple
import attr
from attrs_strict import type_validator

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

try:
SomeClass(names=[("Moo", "Moo"), ("Zoo", 123)])
except ValueError as exception:
print(exception)

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 simple types and types specified in the typing module: List, Dict, DefaultDict,
Set, Union, Tuple, NewType Callable, Literal and any combination of them. This means that you can specify
nested types like List[List[Dict[int, str]]] and the validation would check if attribute has the specific type.
Callable will validate if the callable function's annotation matches the type definition. If type does not specify any
annotations then all callables will pass the validation against it. Support for Callable is not available for
python2.
Literal only allows using instances of int, str, bool, Enum or valid Literal types. Type checking Literal
with any other type as argument raises attrs_strict._error.UnsupportedLiteralError.
def fully_annotated_function(self, a: int, b: int) -> str:
...

def un_annonated_function(a, b):
...

@attr.s
class Something(object):
a = attr.ib(
validator=type_validator(), type=typing.Callable
) # Will work for any callable
b = attr.ib(validator=type_validator(), type=typing.Callable[[int, int], str])

Something(a=un_annonated_function, b=fully_annotated_function)

TypeVars or Generics are not supported yet but there are plans to support this in the future.
Building
For development, the project uses tox in order to install dependencies, run tests and
generate documentation. In order to be able to do this, you need tox pip install tox and after that invoke tox in
the root of the project.
Installation
Run pip install attrs-strict to install the latest stable version from PyPi.
Documentation is hosted on readthedocs.
For the latest version, on github pip install git+https://github.com/bloomberg/attrs-strict.