cpython/Lib/test/test_contextlib.py

839 lines
26 KiB
Python

"""Unit tests for contextlib.py, and other context managers."""
import io
import sys
import tempfile
import unittest
from contextlib import * # Tests __all__
from test import support
try:
import threading
except ImportError:
threading = None
class ContextManagerTestCase(unittest.TestCase):
def test_contextmanager_plain(self):
state = []
@contextmanager
def woohoo():
state.append(1)
yield 42
state.append(999)
with woohoo() as x:
self.assertEqual(state, [1])
self.assertEqual(x, 42)
state.append(x)
self.assertEqual(state, [1, 42, 999])
def test_contextmanager_finally(self):
state = []
@contextmanager
def woohoo():
state.append(1)
try:
yield 42
finally:
state.append(999)
with self.assertRaises(ZeroDivisionError):
with woohoo() as x:
self.assertEqual(state, [1])
self.assertEqual(x, 42)
state.append(x)
raise ZeroDivisionError()
self.assertEqual(state, [1, 42, 999])
def test_contextmanager_no_reraise(self):
@contextmanager
def whee():
yield
ctx = whee()
ctx.__enter__()
# Calling __exit__ should not result in an exception
self.assertFalse(ctx.__exit__(TypeError, TypeError("foo"), None))
def test_contextmanager_trap_yield_after_throw(self):
@contextmanager
def whoo():
try:
yield
except:
yield
ctx = whoo()
ctx.__enter__()
self.assertRaises(
RuntimeError, ctx.__exit__, TypeError, TypeError("foo"), None
)
def test_contextmanager_except(self):
state = []
@contextmanager
def woohoo():
state.append(1)
try:
yield 42
except ZeroDivisionError as e:
state.append(e.args[0])
self.assertEqual(state, [1, 42, 999])
with woohoo() as x:
self.assertEqual(state, [1])
self.assertEqual(x, 42)
state.append(x)
raise ZeroDivisionError(999)
self.assertEqual(state, [1, 42, 999])
def _create_contextmanager_attribs(self):
def attribs(**kw):
def decorate(func):
for k,v in kw.items():
setattr(func,k,v)
return func
return decorate
@contextmanager
@attribs(foo='bar')
def baz(spam):
"""Whee!"""
return baz
def test_contextmanager_attribs(self):
baz = self._create_contextmanager_attribs()
self.assertEqual(baz.__name__,'baz')
self.assertEqual(baz.foo, 'bar')
@support.requires_docstrings
def test_contextmanager_doc_attrib(self):
baz = self._create_contextmanager_attribs()
self.assertEqual(baz.__doc__, "Whee!")
@support.requires_docstrings
def test_instance_docstring_given_cm_docstring(self):
baz = self._create_contextmanager_attribs()(None)
self.assertEqual(baz.__doc__, "Whee!")
def test_keywords(self):
# Ensure no keyword arguments are inhibited
@contextmanager
def woohoo(self, func, args, kwds):
yield (self, func, args, kwds)
with woohoo(self=11, func=22, args=33, kwds=44) as target:
self.assertEqual(target, (11, 22, 33, 44))
class ClosingTestCase(unittest.TestCase):
@support.requires_docstrings
def test_instance_docs(self):
# Issue 19330: ensure context manager instances have good docstrings
cm_docstring = closing.__doc__
obj = closing(None)
self.assertEqual(obj.__doc__, cm_docstring)
def test_closing(self):
state = []
class C:
def close(self):
state.append(1)
x = C()
self.assertEqual(state, [])
with closing(x) as y:
self.assertEqual(x, y)
self.assertEqual(state, [1])
def test_closing_error(self):
state = []
class C:
def close(self):
state.append(1)
x = C()
self.assertEqual(state, [])
with self.assertRaises(ZeroDivisionError):
with closing(x) as y:
self.assertEqual(x, y)
1 / 0
self.assertEqual(state, [1])
class FileContextTestCase(unittest.TestCase):
def testWithOpen(self):
tfn = tempfile.mktemp()
try:
f = None
with open(tfn, "w") as f:
self.assertFalse(f.closed)
f.write("Booh\n")
self.assertTrue(f.closed)
f = None
with self.assertRaises(ZeroDivisionError):
with open(tfn, "r") as f:
self.assertFalse(f.closed)
self.assertEqual(f.read(), "Booh\n")
1 / 0
self.assertTrue(f.closed)
finally:
support.unlink(tfn)
@unittest.skipUnless(threading, 'Threading required for this test.')
class LockContextTestCase(unittest.TestCase):
def boilerPlate(self, lock, locked):
self.assertFalse(locked())
with lock:
self.assertTrue(locked())
self.assertFalse(locked())
with self.assertRaises(ZeroDivisionError):
with lock:
self.assertTrue(locked())
1 / 0
self.assertFalse(locked())
def testWithLock(self):
lock = threading.Lock()
self.boilerPlate(lock, lock.locked)
def testWithRLock(self):
lock = threading.RLock()
self.boilerPlate(lock, lock._is_owned)
def testWithCondition(self):
lock = threading.Condition()
def locked():
return lock._is_owned()
self.boilerPlate(lock, locked)
def testWithSemaphore(self):
lock = threading.Semaphore()
def locked():
if lock.acquire(False):
lock.release()
return False
else:
return True
self.boilerPlate(lock, locked)
def testWithBoundedSemaphore(self):
lock = threading.BoundedSemaphore()
def locked():
if lock.acquire(False):
lock.release()
return False
else:
return True
self.boilerPlate(lock, locked)
class mycontext(ContextDecorator):
"""Example decoration-compatible context manager for testing"""
started = False
exc = None
catch = False
def __enter__(self):
self.started = True
return self
def __exit__(self, *exc):
self.exc = exc
return self.catch
class TestContextDecorator(unittest.TestCase):
@support.requires_docstrings
def test_instance_docs(self):
# Issue 19330: ensure context manager instances have good docstrings
cm_docstring = mycontext.__doc__
obj = mycontext()
self.assertEqual(obj.__doc__, cm_docstring)
def test_contextdecorator(self):
context = mycontext()
with context as result:
self.assertIs(result, context)
self.assertTrue(context.started)
self.assertEqual(context.exc, (None, None, None))
def test_contextdecorator_with_exception(self):
context = mycontext()
with self.assertRaisesRegex(NameError, 'foo'):
with context:
raise NameError('foo')
self.assertIsNotNone(context.exc)
self.assertIs(context.exc[0], NameError)
context = mycontext()
context.catch = True
with context:
raise NameError('foo')
self.assertIsNotNone(context.exc)
self.assertIs(context.exc[0], NameError)
def test_decorator(self):
context = mycontext()
@context
def test():
self.assertIsNone(context.exc)
self.assertTrue(context.started)
test()
self.assertEqual(context.exc, (None, None, None))
def test_decorator_with_exception(self):
context = mycontext()
@context
def test():
self.assertIsNone(context.exc)
self.assertTrue(context.started)
raise NameError('foo')
with self.assertRaisesRegex(NameError, 'foo'):
test()
self.assertIsNotNone(context.exc)
self.assertIs(context.exc[0], NameError)
def test_decorating_method(self):
context = mycontext()
class Test(object):
@context
def method(self, a, b, c=None):
self.a = a
self.b = b
self.c = c
# these tests are for argument passing when used as a decorator
test = Test()
test.method(1, 2)
self.assertEqual(test.a, 1)
self.assertEqual(test.b, 2)
self.assertEqual(test.c, None)
test = Test()
test.method('a', 'b', 'c')
self.assertEqual(test.a, 'a')
self.assertEqual(test.b, 'b')
self.assertEqual(test.c, 'c')
test = Test()
test.method(a=1, b=2)
self.assertEqual(test.a, 1)
self.assertEqual(test.b, 2)
def test_typo_enter(self):
class mycontext(ContextDecorator):
def __unter__(self):
pass
def __exit__(self, *exc):
pass
with self.assertRaises(AttributeError):
with mycontext():
pass
def test_typo_exit(self):
class mycontext(ContextDecorator):
def __enter__(self):
pass
def __uxit__(self, *exc):
pass
with self.assertRaises(AttributeError):
with mycontext():
pass
def test_contextdecorator_as_mixin(self):
class somecontext(object):
started = False
exc = None
def __enter__(self):
self.started = True
return self
def __exit__(self, *exc):
self.exc = exc
class mycontext(somecontext, ContextDecorator):
pass
context = mycontext()
@context
def test():
self.assertIsNone(context.exc)
self.assertTrue(context.started)
test()
self.assertEqual(context.exc, (None, None, None))
def test_contextmanager_as_decorator(self):
@contextmanager
def woohoo(y):
state.append(y)
yield
state.append(999)
state = []
@woohoo(1)
def test(x):
self.assertEqual(state, [1])
state.append(x)
test('something')
self.assertEqual(state, [1, 'something', 999])
# Issue #11647: Ensure the decorated function is 'reusable'
state = []
test('something else')
self.assertEqual(state, [1, 'something else', 999])
class TestExitStack(unittest.TestCase):
@support.requires_docstrings
def test_instance_docs(self):
# Issue 19330: ensure context manager instances have good docstrings
cm_docstring = ExitStack.__doc__
obj = ExitStack()
self.assertEqual(obj.__doc__, cm_docstring)
def test_no_resources(self):
with ExitStack():
pass
def test_callback(self):
expected = [
((), {}),
((1,), {}),
((1,2), {}),
((), dict(example=1)),
((1,), dict(example=1)),
((1,2), dict(example=1)),
]
result = []
def _exit(*args, **kwds):
"""Test metadata propagation"""
result.append((args, kwds))
with ExitStack() as stack:
for args, kwds in reversed(expected):
if args and kwds:
f = stack.callback(_exit, *args, **kwds)
elif args:
f = stack.callback(_exit, *args)
elif kwds:
f = stack.callback(_exit, **kwds)
else:
f = stack.callback(_exit)
self.assertIs(f, _exit)
for wrapper in stack._exit_callbacks:
self.assertIs(wrapper.__wrapped__, _exit)
self.assertNotEqual(wrapper.__name__, _exit.__name__)
self.assertIsNone(wrapper.__doc__, _exit.__doc__)
self.assertEqual(result, expected)
def test_push(self):
exc_raised = ZeroDivisionError
def _expect_exc(exc_type, exc, exc_tb):
self.assertIs(exc_type, exc_raised)
def _suppress_exc(*exc_details):
return True
def _expect_ok(exc_type, exc, exc_tb):
self.assertIsNone(exc_type)
self.assertIsNone(exc)
self.assertIsNone(exc_tb)
class ExitCM(object):
def __init__(self, check_exc):
self.check_exc = check_exc
def __enter__(self):
self.fail("Should not be called!")
def __exit__(self, *exc_details):
self.check_exc(*exc_details)
with ExitStack() as stack:
stack.push(_expect_ok)
self.assertIs(stack._exit_callbacks[-1], _expect_ok)
cm = ExitCM(_expect_ok)
stack.push(cm)
self.assertIs(stack._exit_callbacks[-1].__self__, cm)
stack.push(_suppress_exc)
self.assertIs(stack._exit_callbacks[-1], _suppress_exc)
cm = ExitCM(_expect_exc)
stack.push(cm)
self.assertIs(stack._exit_callbacks[-1].__self__, cm)
stack.push(_expect_exc)
self.assertIs(stack._exit_callbacks[-1], _expect_exc)
stack.push(_expect_exc)
self.assertIs(stack._exit_callbacks[-1], _expect_exc)
1/0
def test_enter_context(self):
class TestCM(object):
def __enter__(self):
result.append(1)
def __exit__(self, *exc_details):
result.append(3)
result = []
cm = TestCM()
with ExitStack() as stack:
@stack.callback # Registered first => cleaned up last
def _exit():
result.append(4)
self.assertIsNotNone(_exit)
stack.enter_context(cm)
self.assertIs(stack._exit_callbacks[-1].__self__, cm)
result.append(2)
self.assertEqual(result, [1, 2, 3, 4])
def test_close(self):
result = []
with ExitStack() as stack:
@stack.callback
def _exit():
result.append(1)
self.assertIsNotNone(_exit)
stack.close()
result.append(2)
self.assertEqual(result, [1, 2])
def test_pop_all(self):
result = []
with ExitStack() as stack:
@stack.callback
def _exit():
result.append(3)
self.assertIsNotNone(_exit)
new_stack = stack.pop_all()
result.append(1)
result.append(2)
new_stack.close()
self.assertEqual(result, [1, 2, 3])
def test_exit_raise(self):
with self.assertRaises(ZeroDivisionError):
with ExitStack() as stack:
stack.push(lambda *exc: False)
1/0
def test_exit_suppress(self):
with ExitStack() as stack:
stack.push(lambda *exc: True)
1/0
def test_exit_exception_chaining_reference(self):
# Sanity check to make sure that ExitStack chaining matches
# actual nested with statements
class RaiseExc:
def __init__(self, exc):
self.exc = exc
def __enter__(self):
return self
def __exit__(self, *exc_details):
raise self.exc
class RaiseExcWithContext:
def __init__(self, outer, inner):
self.outer = outer
self.inner = inner
def __enter__(self):
return self
def __exit__(self, *exc_details):
try:
raise self.inner
except:
raise self.outer
class SuppressExc:
def __enter__(self):
return self
def __exit__(self, *exc_details):
type(self).saved_details = exc_details
return True
try:
with RaiseExc(IndexError):
with RaiseExcWithContext(KeyError, AttributeError):
with SuppressExc():
with RaiseExc(ValueError):
1 / 0
except IndexError as exc:
self.assertIsInstance(exc.__context__, KeyError)
self.assertIsInstance(exc.__context__.__context__, AttributeError)
# Inner exceptions were suppressed
self.assertIsNone(exc.__context__.__context__.__context__)
else:
self.fail("Expected IndexError, but no exception was raised")
# Check the inner exceptions
inner_exc = SuppressExc.saved_details[1]
self.assertIsInstance(inner_exc, ValueError)
self.assertIsInstance(inner_exc.__context__, ZeroDivisionError)
def test_exit_exception_chaining(self):
# Ensure exception chaining matches the reference behaviour
def raise_exc(exc):
raise exc
saved_details = None
def suppress_exc(*exc_details):
nonlocal saved_details
saved_details = exc_details
return True
try:
with ExitStack() as stack:
stack.callback(raise_exc, IndexError)
stack.callback(raise_exc, KeyError)
stack.callback(raise_exc, AttributeError)
stack.push(suppress_exc)
stack.callback(raise_exc, ValueError)
1 / 0
except IndexError as exc:
self.assertIsInstance(exc.__context__, KeyError)
self.assertIsInstance(exc.__context__.__context__, AttributeError)
# Inner exceptions were suppressed
self.assertIsNone(exc.__context__.__context__.__context__)
else:
self.fail("Expected IndexError, but no exception was raised")
# Check the inner exceptions
inner_exc = saved_details[1]
self.assertIsInstance(inner_exc, ValueError)
self.assertIsInstance(inner_exc.__context__, ZeroDivisionError)
def test_exit_exception_non_suppressing(self):
# http://bugs.python.org/issue19092
def raise_exc(exc):
raise exc
def suppress_exc(*exc_details):
return True
try:
with ExitStack() as stack:
stack.callback(lambda: None)
stack.callback(raise_exc, IndexError)
except Exception as exc:
self.assertIsInstance(exc, IndexError)
else:
self.fail("Expected IndexError, but no exception was raised")
try:
with ExitStack() as stack:
stack.callback(raise_exc, KeyError)
stack.push(suppress_exc)
stack.callback(raise_exc, IndexError)
except Exception as exc:
self.assertIsInstance(exc, KeyError)
else:
self.fail("Expected KeyError, but no exception was raised")
def test_exit_exception_with_correct_context(self):
# http://bugs.python.org/issue20317
@contextmanager
def gets_the_context_right(exc):
try:
yield
finally:
raise exc
exc1 = Exception(1)
exc2 = Exception(2)
exc3 = Exception(3)
exc4 = Exception(4)
# The contextmanager already fixes the context, so prior to the
# fix, ExitStack would try to fix it *again* and get into an
# infinite self-referential loop
try:
with ExitStack() as stack:
stack.enter_context(gets_the_context_right(exc4))
stack.enter_context(gets_the_context_right(exc3))
stack.enter_context(gets_the_context_right(exc2))
raise exc1
except Exception as exc:
self.assertIs(exc, exc4)
self.assertIs(exc.__context__, exc3)
self.assertIs(exc.__context__.__context__, exc2)
self.assertIs(exc.__context__.__context__.__context__, exc1)
self.assertIsNone(
exc.__context__.__context__.__context__.__context__)
def test_exit_exception_with_existing_context(self):
# Addresses a lack of test coverage discovered after checking in a
# fix for issue 20317 that still contained debugging code.
def raise_nested(inner_exc, outer_exc):
try:
raise inner_exc
finally:
raise outer_exc
exc1 = Exception(1)
exc2 = Exception(2)
exc3 = Exception(3)
exc4 = Exception(4)
exc5 = Exception(5)
try:
with ExitStack() as stack:
stack.callback(raise_nested, exc4, exc5)
stack.callback(raise_nested, exc2, exc3)
raise exc1
except Exception as exc:
self.assertIs(exc, exc5)
self.assertIs(exc.__context__, exc4)
self.assertIs(exc.__context__.__context__, exc3)
self.assertIs(exc.__context__.__context__.__context__, exc2)
self.assertIs(
exc.__context__.__context__.__context__.__context__, exc1)
self.assertIsNone(
exc.__context__.__context__.__context__.__context__.__context__)
def test_body_exception_suppress(self):
def suppress_exc(*exc_details):
return True
try:
with ExitStack() as stack:
stack.push(suppress_exc)
1/0
except IndexError as exc:
self.fail("Expected no exception, got IndexError")
def test_exit_exception_chaining_suppress(self):
with ExitStack() as stack:
stack.push(lambda *exc: True)
stack.push(lambda *exc: 1/0)
stack.push(lambda *exc: {}[1])
def test_excessive_nesting(self):
# The original implementation would die with RecursionError here
with ExitStack() as stack:
for i in range(10000):
stack.callback(int)
def test_instance_bypass(self):
class Example(object): pass
cm = Example()
cm.__exit__ = object()
stack = ExitStack()
self.assertRaises(AttributeError, stack.enter_context, cm)
stack.push(cm)
self.assertIs(stack._exit_callbacks[-1], cm)
class TestRedirectStdout(unittest.TestCase):
@support.requires_docstrings
def test_instance_docs(self):
# Issue 19330: ensure context manager instances have good docstrings
cm_docstring = redirect_stdout.__doc__
obj = redirect_stdout(None)
self.assertEqual(obj.__doc__, cm_docstring)
def test_no_redirect_in_init(self):
orig_stdout = sys.stdout
redirect_stdout(None)
self.assertIs(sys.stdout, orig_stdout)
def test_redirect_to_string_io(self):
f = io.StringIO()
msg = "Consider an API like help(), which prints directly to stdout"
orig_stdout = sys.stdout
with redirect_stdout(f):
print(msg)
self.assertIs(sys.stdout, orig_stdout)
s = f.getvalue().strip()
self.assertEqual(s, msg)
def test_enter_result_is_target(self):
f = io.StringIO()
with redirect_stdout(f) as enter_result:
self.assertIs(enter_result, f)
def test_cm_is_reusable(self):
f = io.StringIO()
write_to_f = redirect_stdout(f)
orig_stdout = sys.stdout
with write_to_f:
print("Hello", end=" ")
with write_to_f:
print("World!")
self.assertIs(sys.stdout, orig_stdout)
s = f.getvalue()
self.assertEqual(s, "Hello World!\n")
def test_cm_is_reentrant(self):
f = io.StringIO()
write_to_f = redirect_stdout(f)
orig_stdout = sys.stdout
with write_to_f:
print("Hello", end=" ")
with write_to_f:
print("World!")
self.assertIs(sys.stdout, orig_stdout)
s = f.getvalue()
self.assertEqual(s, "Hello World!\n")
class TestSuppress(unittest.TestCase):
@support.requires_docstrings
def test_instance_docs(self):
# Issue 19330: ensure context manager instances have good docstrings
cm_docstring = suppress.__doc__
obj = suppress()
self.assertEqual(obj.__doc__, cm_docstring)
def test_no_result_from_enter(self):
with suppress(ValueError) as enter_result:
self.assertIsNone(enter_result)
def test_no_exception(self):
with suppress(ValueError):
self.assertEqual(pow(2, 5), 32)
def test_exact_exception(self):
with suppress(TypeError):
len(5)
def test_exception_hierarchy(self):
with suppress(LookupError):
'Hello'[50]
def test_other_exception(self):
with self.assertRaises(ZeroDivisionError):
with suppress(TypeError):
1/0
def test_no_args(self):
with self.assertRaises(ZeroDivisionError):
with suppress():
1/0
def test_multiple_exception_args(self):
with suppress(ZeroDivisionError, TypeError):
1/0
with suppress(ZeroDivisionError, TypeError):
len(5)
def test_cm_is_reentrant(self):
ignore_exceptions = suppress(Exception)
with ignore_exceptions:
pass
with ignore_exceptions:
len(5)
with ignore_exceptions:
with ignore_exceptions: # Check nested usage
len(5)
outer_continued = True
1/0
self.assertTrue(outer_continued)
if __name__ == "__main__":
unittest.main()