Exception Helper

delfick_project provides a custom error class for making working with exceptions a little nicer.

Usage looks like:

from delfick_project.errors import DelfickError

class MyError(DelfickError):
    desc = "something went wrong"

raise MyError("Computer says no", arg1=True, arg2=3)

DelfickError instances have the following properties:

• Instantiation takes a message and arbitrary keyword arguments. if one of the arguments is _errors then this will be treated specially when presenting the error as a string, and will be available on the instance as error.errors

  All other keyword arguments are available under error.kwargs

• __str__ takes into account desc on the class, the message given to the instance, any _errors on the instance and the rest of the keyword arguments.

• error.as_dict() returns the error as a dictionary. a “message” key will combine desc on the class and the message given to the instance. “errors” will be a list of the _errors list as dictionaries (or string for errors that have no as_dict method. And the rest of error.kwargs in the dictionary.

• Instances can be used as keys in a dictionary. It matches on a tuple of (error_kls, messages, kwargs_as_tuple, errors_as_tuple)

• Instances can be used in an equality check based off the same information used to make it hashable

• Instances are sortable

This module also provides:

class delfick_project.errors.ProgrammerError

A non DelfickError exception for when the programmer should have prevented something happening

class delfick_project.errors.UserQuit(message='', **kwargs)

Raise this if the user quit the application

class delfick_project.errors.DelfickErrorTestMixin

A mixin for use with unittest.TestCase that provides the ability to test for DelfickError exceptions.

from delfick_project.errors import DelfickErrorTestMixin

from unittest import TestCase

class TestThings(TestCase, DelfickErrorTestMixin):
    def test_something(self):
        error1 = DelfickError("something bad happend")
        with self.fuzzyAssertRaisesError(MyError, "nope", arg1=2, _errors=[error1]):
            raise MyError("nope", arg1=2, arg2=3, _errors=[error1])

fuzzyAssertRaisesError(expected_kls, expected_msg_regex=<class 'delfick_project.errors.Empty'>, **values)

Assert that something raises a particular type of error.

The error raised must be a subclass of the expected_kls Have a message that matches the specified regex.

And have atleast the values specified in it’s kwargs.

delfick_project.errors_pytest.assertRaises(expected_kls, expected_msg_regex=<class 'delfick_project.errors_pytest.Empty'>, **values)

Assert that something raises a particular type of error.

The error raised must be a subclass of the expected_kls Have a message that matches the specified regex.

And have atleast the values specified in it’s kwargs.

This is the same as fuzzyAssertRaisesError in DelfickErrorTestMixin but more suitable to use in pytest.

from delficK-project.errors_pytest import assertRaises

def test_something():
    error1 = DelfickError("something bad happend")
    with assertRaises(MyError, "nope", arg1=2, _errors=[error1]):
        raise MyError("nope", arg1=2, arg2=3, _errors=[error1])