Snippet

Capturing and Structuring Exceptions in Custom Signal Handlers

Django's `send_robust` allows signal handlers to fail without interrupting execution, returning exception instances instead of raising them immediately. This helper aggregates those raised exceptions into a single structured report.

snippet.py

python

from django.dispatch import Signal
from django.core.exceptions import ValidationError
import logging
 
logger = logging.getLogger(__name__)
user_action_signal = Signal()
 
def safe_signal_dispatch(signal, sender, **kwargs):
    results = signal.send_robust(sender=sender, **kwargs)
    errors = []
    for receiver, response in results:
        if isinstance(response, Exception):
            logger.error(f'Error in {receiver}: {response}')
            errors.append((receiver, response))
    if errors:
        raise ValidationError(f'Signal dispatch completed with {len(errors)} errors.')
    return results

django

Breakdown

user_action_signal = Signal()

Instantiates a custom Django signal dispatcher instance.

results = signal.send_robust(sender=sender, **kwargs)

Executes all registered receivers, catching exceptions per handler and returning pairs of (receiver, response_or_exception).

if isinstance(response, Exception):

Inspects each handler result to identify whether an uncaught exception occurred within the signal receiver.

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Capturing and Structuring Exceptions in Custom Signal Handlers

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