prejudice

This package helps defining and creating small and reusable components that can serve as guard or validation methods.

Example

Below is an example of a validation on a content item.

from dataclasses import dataclass
from prejudice.errors import ConstraintError
from prejudice.validators import Or


@dataclass
class Document:
    id: str
    body: str = ''
    content_type: str = 'text/plain'


def non_empty_document(item):
    """Implementation of a validator/predicate
    """
    if not item.body:
        raise ConstraintError('Body is empty.')


class ContentType:

    def __init__(self, content_type):
        self.ct = content_type

    def __call__(self, item):
        if item.content_type != self.ct:
            raise ConstraintError(
                f'Expected {self.ct}, got {item.content_type}.')


  validator = Or((
      ContentType('text/plain'),
      Or((ContentType('text/html'), non_empty_document))
  ))
  document = Document(id='test', content_type='application/json')
  validator(document)  # raises ConstraintsErrors