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"""
Error-handling utility code.
"""
from inspect import getmro
class ErrorExtraction(object):
"""
Extract fields from exceptions for failed-action messages.
@ivar registry: Map exception class to function that extracts fields.
"""
def __init__(self):
self.registry = {}
def register_exception_extractor(self, exception_class, extractor):
"""
Register a function that converts exceptions to fields.
@param exception_class: Class to register for.
@param extractor: Single-argument callable that takes an exception
of the given class (or a subclass) and returns a dictionary,
fields to include in a failed action message.
"""
self.registry[exception_class] = extractor
def get_fields_for_exception(self, logger, exception):
"""
Given an exception instance, return fields to add to the failed action
message.
@param logger: ``ILogger`` currently being used.
@param exception: An exception instance.
@return: Dictionary with fields to include.
"""
for klass in getmro(exception.__class__):
if klass in self.registry:
extractor = self.registry[klass]
try:
return extractor(exception)
except:
from ._traceback import write_traceback
write_traceback(logger)
return {}
return {}
_error_extraction = ErrorExtraction()
register_exception_extractor = _error_extraction.register_exception_extractor
get_fields_for_exception = _error_extraction.get_fields_for_exception
# Default handler for OSError and IOError by registered EnvironmentError:
register_exception_extractor(EnvironmentError, lambda e: {"errno": e.errno})
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