flexfail 1.0.0

Flexible failures collector with different collect strategies.

flexfail

Flexible failures collector with different collecting strategies.

flexfail provides a consistent and reusable way to collect, and handle failures. Useful in data processing, form validation, and other contexts where soft-failing logic is needed.

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Justification

Why? Imagine you're processing a batch of data sent from a user and want to return a meaningful error description if something goes wrong. Suppose the data contains 3 different errors in separate places. In a naive implementation, you might return only one error per request. This would force the user to resubmit the request multiple times to fix everything.

This library aims to make error collection simpler, clearer, and more flexible.

It allows you to collect all errors in the data at once, if needed - or just return the first encountered error. You may even choose to skip invalid values silently. This behavior is controlled by predefined error collection strategies (see examples below).

Moreover, in our example, user may choose what strategy is more suitable for them.

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Installation

pip install flexfail

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Examples

Prerequisites before strategies overview

Below is a simple example of how flexfail can be used to wrap a function and handle failures using different strategies:

from flexfail import ErrorCollector, ErrorCollectorStrategy
from flexfail.exceptions import FlexFailException, FailFastException


# Let's assume, negative values are impossible to process, as the values are checkouts, for instance.
checkouts = [10, 20, -30, -40, 50, 'spam']


def process_check(value: float):
    if not isinstance(value, (float, int)):
        raise FlexFailException(data={'description': 'Checkout value is not a number!', 'value': value})
    if value < 0:
        raise FlexFailException(data={'description': 'Checkout value was below zero!', 'value': value})
    print(f'Check with amount {value}$ was successfully processed!')


def process_all_with_strategy(strategy: ErrorCollectorStrategy):
    error_collector = ErrorCollector(process_check, strategy)
    try:
        for _ in checkouts:
            error_collector.call(_)
    except FailFastException:
        pass
    print(f'Collected errors:')
    for error in error_collector.errors:
        print(error.data)

Please, note, only FlexFailException is safe to raise. If you need any other exception to be collected, just wrap it, using the data. You'll be able to access it later. Example:

raise FlexFailException(data={'my_wrapped_exception': RuntimeError('Some custom error!')})

Strategy skip

Force bypass all the errors and not even collect them.

process_all_with_strategy(ErrorCollectorStrategy.skip)

Results into:

Check with amount 10$ was successfully processed!
Check with amount 20$ was successfully processed!
Check with amount 50$ was successfully processed!
Collected errors:

Strategy fail_fast

Raise on first error occurs and collect only it.

process_all_with_strategy(ErrorCollectorStrategy.fail_fast)

Results into:

Check with amount 10$ was successfully processed!
Check with amount 20$ was successfully processed!
Collected errors:
{'description': 'Checkout value was below zero!', 'value': -30}

Strategy try_all

Collect all the errors.

process_all_with_strategy(ErrorCollectorStrategy.try_all)

Results into:

Collected errors:
{'description': 'Checkout value was below zero!', 'value': -30}
{'description': 'Checkout value was below zero!', 'value': -40}
{'description': 'Checkout value is not a number!', 'value': 'spam'}