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from __future__ import annotations
import functools
import operator
# from jaraco.context 6.1
class ExceptionTrap:
"""
A context manager that will catch certain exceptions and provide an
indication they occurred.
>>> with ExceptionTrap() as trap:
... raise Exception()
>>> bool(trap)
True
>>> with ExceptionTrap() as trap:
... pass
>>> bool(trap)
False
>>> with ExceptionTrap(ValueError) as trap:
... raise ValueError("1 + 1 is not 3")
>>> bool(trap)
True
>>> trap.value
ValueError('1 + 1 is not 3')
>>> trap.tb
<traceback object at ...>
>>> with ExceptionTrap(ValueError) as trap:
... raise Exception()
Traceback (most recent call last):
...
Exception
>>> bool(trap)
False
"""
exc_info = None, None, None
def __init__(self, exceptions=(Exception,)):
self.exceptions = exceptions
def __enter__(self):
return self
@property
def type(self):
return self.exc_info[0]
@property
def value(self):
return self.exc_info[1]
@property
def tb(self):
return self.exc_info[2]
def __exit__(self, *exc_info):
type = exc_info[0]
matches = type and issubclass(type, self.exceptions)
if matches:
self.exc_info = exc_info
return matches
def __bool__(self):
return bool(self.type)
def raises(self, func, *, _test=bool):
"""
Wrap func and replace the result with the truth
value of the trap (True if an exception occurred).
First, give the decorator an alias to support Python 3.8
Syntax.
>>> raises = ExceptionTrap(ValueError).raises
Now decorate a function that always fails.
>>> @raises
... def fail():
... raise ValueError('failed')
>>> fail()
True
"""
@functools.wraps(func)
def wrapper(*args, **kwargs):
with ExceptionTrap(self.exceptions) as trap:
func(*args, **kwargs)
return _test(trap)
return wrapper
def passes(self, func):
"""
Wrap func and replace the result with the truth
value of the trap (True if no exception).
First, give the decorator an alias to support Python 3.8
Syntax.
>>> passes = ExceptionTrap(ValueError).passes
Now decorate a function that always fails.
>>> @passes
... def fail():
... raise ValueError('failed')
>>> fail()
False
"""
return self.raises(func, _test=operator.not_)
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