Error Handlers | Core-Lib Documentation

Core-Lib error handlers contain decorator and function which can raise exceptions for various scenarios.

StatusCodeException

core_lib.error_handling.status_code_exception.StatusCodeException [source]

StatusCodeException is the primary and single exception used by any Core-Lib.

It serves three primary purposes:

Unified way to handle errors while using Core-Lib.
Reflect any error with a numeric status code.
Bridge between library errors and HTTP Status code.

class StatusCodeException(Exception):
    def __init__(self, status_code: int, *args, **kwargs):
        self.status_code = status_code
        super(StatusCodeException, self).__init__(*args, **kwargs)

Arguments

status_code (int): Status code error to be raised.
*args, **kwargs: The extracted args and kwargs given to the class.

Example

from http import HTTPStatus
from core_lib.error_handling.status_code_exception import StatusCodeException

raise StatusCodeException(HTTPStatus.BAD_REQUEST, 'Input parameter is invalid')

NotFoundErrorHandler Decorator

core_lib.error_handling.not_found_decorator.NotFoundErrorHandler [source]

NotFoundErrorHandler decorator will raise StatusCodeException when the decorated function is not returning anything.
For e.g., if a function is returning an empty string "", tuple (), list [], dict {} set() or None StatusCodeException will be raised.

Example

from core_lib.error_handling.not_found_decorator import NotFoundErrorHandler

@NotFoundErrorHandler()
def raise_expection():
    pass

raise_expection() # will raise a StatusCodeException for parameter NOT_FOUND

StatusCodeAssert Function

core_lib.error_handling.status_code_assert.StatusCodeAssert [source]

Using StatusCodeAssert along with the with statement will capture any AssertionError and raise StatusCodeException with the status and message relevant to the application needs.

Example

from core_lib.error_handling.status_code_assert import StatusCodeAssert

user_status = 'inactive'
with StatusCodeAssert(status_code=500, message="User must be active"):
    assert user_status == 'active' # will raise an AssertionError because the status is inactive.

CoreLibInitException Function

core_lib.error_handling.core_lib_init_exception.CoreLibInitException [source]

CoreLibInitException decorator handles any exception raised while initialization of core-lib.

Example

class CoreLibInitException(Exception):
    pass

DuplicateErrorHandler Function

core_lib.error_handling.duplicate_error_handler.DuplicateErrorHandler [source]

DuplicateErrorHandler decorator will raise StatusCodeException when the decorated function adds the same value in the column of the database table which accepts unique values only.

Example

import logging
from functools import wraps
from http import HTTPStatus

from sqlalchemy import exc

from core_lib.error_handling.status_code_exception import StatusCodeException
from core_lib.helpers.func_utils import build_function_key

logger = logging.getLogger(__name__)


class DuplicateErrorHandler(object):
    def __init__(self, message: str = None):
        self.message = message

    def __call__(self, func, *args, **kwargs):
        @wraps(func)
        def _wrapper(*args, **kwargs):
            try:
                return func(*args, **kwargs)
            except exc.IntegrityError as e:
                logger.debug(f'DuplicateErrorHandler for function `{func.__qualname__}`.')
                exception_message = build_function_key(self.message, func, *args, **kwargs) if self.message else None
                raise StatusCodeException(HTTPStatus.CONFLICT, exception_message)

        return _wrapper