cpython/Lib/test/test_with.py
Amaury Forgeot d'Arc 10b24e87e5 Merged revisions 67688 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk

........
  r67688 | amaury.forgeotdarc | 2008-12-11 00:22:49 +0100 (jeu., 11 déc. 2008) | 6 lines

  #4559: When a context manager's __exit__() method returns an object whose
  conversion to bool raises an exception, 'with' loses that exception.

  Reviewed by Jeffrey Yasskin.
  Already ported to 2.5, will port to 2.6 and 3.0
........
2008-12-10 23:49:33 +00:00

669 lines
23 KiB
Python

#!/usr/bin/env python
"""Unit tests for the with statement specified in PEP 343."""
__author__ = "Mike Bland"
__email__ = "mbland at acm dot org"
import sys
import unittest
from collections import deque
from contextlib import GeneratorContextManager, contextmanager
from test.support import run_unittest
class MockContextManager(GeneratorContextManager):
def __init__(self, gen):
GeneratorContextManager.__init__(self, gen)
self.enter_called = False
self.exit_called = False
self.exit_args = None
def __enter__(self):
self.enter_called = True
return GeneratorContextManager.__enter__(self)
def __exit__(self, type, value, traceback):
self.exit_called = True
self.exit_args = (type, value, traceback)
return GeneratorContextManager.__exit__(self, type,
value, traceback)
def mock_contextmanager(func):
def helper(*args, **kwds):
return MockContextManager(func(*args, **kwds))
return helper
class MockResource(object):
def __init__(self):
self.yielded = False
self.stopped = False
@mock_contextmanager
def mock_contextmanager_generator():
mock = MockResource()
try:
mock.yielded = True
yield mock
finally:
mock.stopped = True
class Nested(object):
def __init__(self, *managers):
self.managers = managers
self.entered = None
def __enter__(self):
if self.entered is not None:
raise RuntimeError("Context is not reentrant")
self.entered = deque()
vars = []
try:
for mgr in self.managers:
vars.append(mgr.__enter__())
self.entered.appendleft(mgr)
except:
if not self.__exit__(*sys.exc_info()):
raise
return vars
def __exit__(self, *exc_info):
# Behave like nested with statements
# first in, last out
# New exceptions override old ones
ex = exc_info
for mgr in self.entered:
try:
if mgr.__exit__(*ex):
ex = (None, None, None)
except:
ex = sys.exc_info()
self.entered = None
if ex is not exc_info:
raise ex[0](ex[1]).with_traceback(ex[2])
class MockNested(Nested):
def __init__(self, *managers):
Nested.__init__(self, *managers)
self.enter_called = False
self.exit_called = False
self.exit_args = None
def __enter__(self):
self.enter_called = True
return Nested.__enter__(self)
def __exit__(self, *exc_info):
self.exit_called = True
self.exit_args = exc_info
return Nested.__exit__(self, *exc_info)
class FailureTestCase(unittest.TestCase):
def testNameError(self):
def fooNotDeclared():
with foo: pass
self.assertRaises(NameError, fooNotDeclared)
def testEnterAttributeError(self):
class LacksEnter(object):
def __exit__(self, type, value, traceback):
pass
def fooLacksEnter():
foo = LacksEnter()
with foo: pass
self.assertRaises(AttributeError, fooLacksEnter)
def testExitAttributeError(self):
class LacksExit(object):
def __enter__(self):
pass
def fooLacksExit():
foo = LacksExit()
with foo: pass
self.assertRaises(AttributeError, fooLacksExit)
def assertRaisesSyntaxError(self, codestr):
def shouldRaiseSyntaxError(s):
compile(s, '', 'single')
self.assertRaises(SyntaxError, shouldRaiseSyntaxError, codestr)
def testAssignmentToNoneError(self):
self.assertRaisesSyntaxError('with mock as None:\n pass')
self.assertRaisesSyntaxError(
'with mock as (None):\n'
' pass')
def testAssignmentToEmptyTupleError(self):
self.assertRaisesSyntaxError(
'with mock as ():\n'
' pass')
def testAssignmentToTupleOnlyContainingNoneError(self):
self.assertRaisesSyntaxError('with mock as None,:\n pass')
self.assertRaisesSyntaxError(
'with mock as (None,):\n'
' pass')
def testAssignmentToTupleContainingNoneError(self):
self.assertRaisesSyntaxError(
'with mock as (foo, None, bar):\n'
' pass')
def testEnterThrows(self):
class EnterThrows(object):
def __enter__(self):
raise RuntimeError("Enter threw")
def __exit__(self, *args):
pass
def shouldThrow():
ct = EnterThrows()
self.foo = None
with ct as self.foo:
pass
self.assertRaises(RuntimeError, shouldThrow)
self.assertEqual(self.foo, None)
def testExitThrows(self):
class ExitThrows(object):
def __enter__(self):
return
def __exit__(self, *args):
raise RuntimeError(42)
def shouldThrow():
with ExitThrows():
pass
self.assertRaises(RuntimeError, shouldThrow)
class ContextmanagerAssertionMixin(object):
def setUp(self):
self.TEST_EXCEPTION = RuntimeError("test exception")
def assertInWithManagerInvariants(self, mock_manager):
self.assertTrue(mock_manager.enter_called)
self.assertFalse(mock_manager.exit_called)
self.assertEqual(mock_manager.exit_args, None)
def assertAfterWithManagerInvariants(self, mock_manager, exit_args):
self.assertTrue(mock_manager.enter_called)
self.assertTrue(mock_manager.exit_called)
self.assertEqual(mock_manager.exit_args, exit_args)
def assertAfterWithManagerInvariantsNoError(self, mock_manager):
self.assertAfterWithManagerInvariants(mock_manager,
(None, None, None))
def assertInWithGeneratorInvariants(self, mock_generator):
self.assertTrue(mock_generator.yielded)
self.assertFalse(mock_generator.stopped)
def assertAfterWithGeneratorInvariantsNoError(self, mock_generator):
self.assertTrue(mock_generator.yielded)
self.assertTrue(mock_generator.stopped)
def raiseTestException(self):
raise self.TEST_EXCEPTION
def assertAfterWithManagerInvariantsWithError(self, mock_manager):
self.assertTrue(mock_manager.enter_called)
self.assertTrue(mock_manager.exit_called)
self.assertEqual(mock_manager.exit_args[0], RuntimeError)
self.assertEqual(mock_manager.exit_args[1], self.TEST_EXCEPTION)
def assertAfterWithGeneratorInvariantsWithError(self, mock_generator):
self.assertTrue(mock_generator.yielded)
self.assertTrue(mock_generator.stopped)
class NonexceptionalTestCase(unittest.TestCase, ContextmanagerAssertionMixin):
def testInlineGeneratorSyntax(self):
with mock_contextmanager_generator():
pass
def testUnboundGenerator(self):
mock = mock_contextmanager_generator()
with mock:
pass
self.assertAfterWithManagerInvariantsNoError(mock)
def testInlineGeneratorBoundSyntax(self):
with mock_contextmanager_generator() as foo:
self.assertInWithGeneratorInvariants(foo)
# FIXME: In the future, we'll try to keep the bound names from leaking
self.assertAfterWithGeneratorInvariantsNoError(foo)
def testInlineGeneratorBoundToExistingVariable(self):
foo = None
with mock_contextmanager_generator() as foo:
self.assertInWithGeneratorInvariants(foo)
self.assertAfterWithGeneratorInvariantsNoError(foo)
def testInlineGeneratorBoundToDottedVariable(self):
with mock_contextmanager_generator() as self.foo:
self.assertInWithGeneratorInvariants(self.foo)
self.assertAfterWithGeneratorInvariantsNoError(self.foo)
def testBoundGenerator(self):
mock = mock_contextmanager_generator()
with mock as foo:
self.assertInWithGeneratorInvariants(foo)
self.assertInWithManagerInvariants(mock)
self.assertAfterWithGeneratorInvariantsNoError(foo)
self.assertAfterWithManagerInvariantsNoError(mock)
def testNestedSingleStatements(self):
mock_a = mock_contextmanager_generator()
with mock_a as foo:
mock_b = mock_contextmanager_generator()
with mock_b as bar:
self.assertInWithManagerInvariants(mock_a)
self.assertInWithManagerInvariants(mock_b)
self.assertInWithGeneratorInvariants(foo)
self.assertInWithGeneratorInvariants(bar)
self.assertAfterWithManagerInvariantsNoError(mock_b)
self.assertAfterWithGeneratorInvariantsNoError(bar)
self.assertInWithManagerInvariants(mock_a)
self.assertInWithGeneratorInvariants(foo)
self.assertAfterWithManagerInvariantsNoError(mock_a)
self.assertAfterWithGeneratorInvariantsNoError(foo)
class NestedNonexceptionalTestCase(unittest.TestCase,
ContextmanagerAssertionMixin):
def testSingleArgInlineGeneratorSyntax(self):
with Nested(mock_contextmanager_generator()):
pass
def testSingleArgUnbound(self):
mock_contextmanager = mock_contextmanager_generator()
mock_nested = MockNested(mock_contextmanager)
with mock_nested:
self.assertInWithManagerInvariants(mock_contextmanager)
self.assertInWithManagerInvariants(mock_nested)
self.assertAfterWithManagerInvariantsNoError(mock_contextmanager)
self.assertAfterWithManagerInvariantsNoError(mock_nested)
def testSingleArgBoundToNonTuple(self):
m = mock_contextmanager_generator()
# This will bind all the arguments to nested() into a single list
# assigned to foo.
with Nested(m) as foo:
self.assertInWithManagerInvariants(m)
self.assertAfterWithManagerInvariantsNoError(m)
def testSingleArgBoundToSingleElementParenthesizedList(self):
m = mock_contextmanager_generator()
# This will bind all the arguments to nested() into a single list
# assigned to foo.
with Nested(m) as (foo):
self.assertInWithManagerInvariants(m)
self.assertAfterWithManagerInvariantsNoError(m)
def testSingleArgBoundToMultipleElementTupleError(self):
def shouldThrowValueError():
with Nested(mock_contextmanager_generator()) as (foo, bar):
pass
self.assertRaises(ValueError, shouldThrowValueError)
def testSingleArgUnbound(self):
mock_contextmanager = mock_contextmanager_generator()
mock_nested = MockNested(mock_contextmanager)
with mock_nested:
self.assertInWithManagerInvariants(mock_contextmanager)
self.assertInWithManagerInvariants(mock_nested)
self.assertAfterWithManagerInvariantsNoError(mock_contextmanager)
self.assertAfterWithManagerInvariantsNoError(mock_nested)
def testMultipleArgUnbound(self):
m = mock_contextmanager_generator()
n = mock_contextmanager_generator()
o = mock_contextmanager_generator()
mock_nested = MockNested(m, n, o)
with mock_nested:
self.assertInWithManagerInvariants(m)
self.assertInWithManagerInvariants(n)
self.assertInWithManagerInvariants(o)
self.assertInWithManagerInvariants(mock_nested)
self.assertAfterWithManagerInvariantsNoError(m)
self.assertAfterWithManagerInvariantsNoError(n)
self.assertAfterWithManagerInvariantsNoError(o)
self.assertAfterWithManagerInvariantsNoError(mock_nested)
def testMultipleArgBound(self):
mock_nested = MockNested(mock_contextmanager_generator(),
mock_contextmanager_generator(), mock_contextmanager_generator())
with mock_nested as (m, n, o):
self.assertInWithGeneratorInvariants(m)
self.assertInWithGeneratorInvariants(n)
self.assertInWithGeneratorInvariants(o)
self.assertInWithManagerInvariants(mock_nested)
self.assertAfterWithGeneratorInvariantsNoError(m)
self.assertAfterWithGeneratorInvariantsNoError(n)
self.assertAfterWithGeneratorInvariantsNoError(o)
self.assertAfterWithManagerInvariantsNoError(mock_nested)
class ExceptionalTestCase(ContextmanagerAssertionMixin, unittest.TestCase):
def testSingleResource(self):
cm = mock_contextmanager_generator()
def shouldThrow():
with cm as self.resource:
self.assertInWithManagerInvariants(cm)
self.assertInWithGeneratorInvariants(self.resource)
self.raiseTestException()
self.assertRaises(RuntimeError, shouldThrow)
self.assertAfterWithManagerInvariantsWithError(cm)
self.assertAfterWithGeneratorInvariantsWithError(self.resource)
def testNestedSingleStatements(self):
mock_a = mock_contextmanager_generator()
mock_b = mock_contextmanager_generator()
def shouldThrow():
with mock_a as self.foo:
with mock_b as self.bar:
self.assertInWithManagerInvariants(mock_a)
self.assertInWithManagerInvariants(mock_b)
self.assertInWithGeneratorInvariants(self.foo)
self.assertInWithGeneratorInvariants(self.bar)
self.raiseTestException()
self.assertRaises(RuntimeError, shouldThrow)
self.assertAfterWithManagerInvariantsWithError(mock_a)
self.assertAfterWithManagerInvariantsWithError(mock_b)
self.assertAfterWithGeneratorInvariantsWithError(self.foo)
self.assertAfterWithGeneratorInvariantsWithError(self.bar)
def testMultipleResourcesInSingleStatement(self):
cm_a = mock_contextmanager_generator()
cm_b = mock_contextmanager_generator()
mock_nested = MockNested(cm_a, cm_b)
def shouldThrow():
with mock_nested as (self.resource_a, self.resource_b):
self.assertInWithManagerInvariants(cm_a)
self.assertInWithManagerInvariants(cm_b)
self.assertInWithManagerInvariants(mock_nested)
self.assertInWithGeneratorInvariants(self.resource_a)
self.assertInWithGeneratorInvariants(self.resource_b)
self.raiseTestException()
self.assertRaises(RuntimeError, shouldThrow)
self.assertAfterWithManagerInvariantsWithError(cm_a)
self.assertAfterWithManagerInvariantsWithError(cm_b)
self.assertAfterWithManagerInvariantsWithError(mock_nested)
self.assertAfterWithGeneratorInvariantsWithError(self.resource_a)
self.assertAfterWithGeneratorInvariantsWithError(self.resource_b)
def testNestedExceptionBeforeInnerStatement(self):
mock_a = mock_contextmanager_generator()
mock_b = mock_contextmanager_generator()
self.bar = None
def shouldThrow():
with mock_a as self.foo:
self.assertInWithManagerInvariants(mock_a)
self.assertInWithGeneratorInvariants(self.foo)
self.raiseTestException()
with mock_b as self.bar:
pass
self.assertRaises(RuntimeError, shouldThrow)
self.assertAfterWithManagerInvariantsWithError(mock_a)
self.assertAfterWithGeneratorInvariantsWithError(self.foo)
# The inner statement stuff should never have been touched
self.assertEqual(self.bar, None)
self.assertFalse(mock_b.enter_called)
self.assertFalse(mock_b.exit_called)
self.assertEqual(mock_b.exit_args, None)
def testNestedExceptionAfterInnerStatement(self):
mock_a = mock_contextmanager_generator()
mock_b = mock_contextmanager_generator()
def shouldThrow():
with mock_a as self.foo:
with mock_b as self.bar:
self.assertInWithManagerInvariants(mock_a)
self.assertInWithManagerInvariants(mock_b)
self.assertInWithGeneratorInvariants(self.foo)
self.assertInWithGeneratorInvariants(self.bar)
self.raiseTestException()
self.assertRaises(RuntimeError, shouldThrow)
self.assertAfterWithManagerInvariantsWithError(mock_a)
self.assertAfterWithManagerInvariantsNoError(mock_b)
self.assertAfterWithGeneratorInvariantsWithError(self.foo)
self.assertAfterWithGeneratorInvariantsNoError(self.bar)
def testRaisedStopIteration1(self):
# From bug 1462485
@contextmanager
def cm():
yield
def shouldThrow():
with cm():
raise StopIteration("from with")
self.assertRaises(StopIteration, shouldThrow)
def testRaisedStopIteration2(self):
# From bug 1462485
class cm(object):
def __enter__(self):
pass
def __exit__(self, type, value, traceback):
pass
def shouldThrow():
with cm():
raise StopIteration("from with")
self.assertRaises(StopIteration, shouldThrow)
def testRaisedStopIteration3(self):
# Another variant where the exception hasn't been instantiated
# From bug 1705170
@contextmanager
def cm():
yield
def shouldThrow():
with cm():
raise next(iter([]))
self.assertRaises(StopIteration, shouldThrow)
def testRaisedGeneratorExit1(self):
# From bug 1462485
@contextmanager
def cm():
yield
def shouldThrow():
with cm():
raise GeneratorExit("from with")
self.assertRaises(GeneratorExit, shouldThrow)
def testRaisedGeneratorExit2(self):
# From bug 1462485
class cm (object):
def __enter__(self):
pass
def __exit__(self, type, value, traceback):
pass
def shouldThrow():
with cm():
raise GeneratorExit("from with")
self.assertRaises(GeneratorExit, shouldThrow)
def testErrorsInBool(self):
# issue4589: __exit__ return code may raise an exception
# when looking at its truth value.
class cm(object):
def __init__(self, bool_conversion):
class Bool:
def __bool__(self):
return bool_conversion()
self.exit_result = Bool()
def __enter__(self):
return 3
def __exit__(self, a, b, c):
return self.exit_result
def trueAsBool():
with cm(lambda: True):
self.fail("Should NOT see this")
trueAsBool()
def falseAsBool():
with cm(lambda: False):
self.fail("Should raise")
self.assertRaises(AssertionError, falseAsBool)
def failAsBool():
with cm(lambda: 1//0):
self.fail("Should NOT see this")
self.assertRaises(ZeroDivisionError, failAsBool)
class NonLocalFlowControlTestCase(unittest.TestCase):
def testWithBreak(self):
counter = 0
while True:
counter += 1
with mock_contextmanager_generator():
counter += 10
break
counter += 100 # Not reached
self.assertEqual(counter, 11)
def testWithContinue(self):
counter = 0
while True:
counter += 1
if counter > 2:
break
with mock_contextmanager_generator():
counter += 10
continue
counter += 100 # Not reached
self.assertEqual(counter, 12)
def testWithReturn(self):
def foo():
counter = 0
while True:
counter += 1
with mock_contextmanager_generator():
counter += 10
return counter
counter += 100 # Not reached
self.assertEqual(foo(), 11)
def testWithYield(self):
def gen():
with mock_contextmanager_generator():
yield 12
yield 13
x = list(gen())
self.assertEqual(x, [12, 13])
def testWithRaise(self):
counter = 0
try:
counter += 1
with mock_contextmanager_generator():
counter += 10
raise RuntimeError
counter += 100 # Not reached
except RuntimeError:
self.assertEqual(counter, 11)
else:
self.fail("Didn't raise RuntimeError")
class AssignmentTargetTestCase(unittest.TestCase):
def testSingleComplexTarget(self):
targets = {1: [0, 1, 2]}
with mock_contextmanager_generator() as targets[1][0]:
self.assertEqual(list(targets.keys()), [1])
self.assertEqual(targets[1][0].__class__, MockResource)
with mock_contextmanager_generator() as list(targets.values())[0][1]:
self.assertEqual(list(targets.keys()), [1])
self.assertEqual(targets[1][1].__class__, MockResource)
with mock_contextmanager_generator() as targets[2]:
keys = list(targets.keys())
keys.sort()
self.assertEqual(keys, [1, 2])
class C: pass
blah = C()
with mock_contextmanager_generator() as blah.foo:
self.assertEqual(hasattr(blah, "foo"), True)
def testMultipleComplexTargets(self):
class C:
def __enter__(self): return 1, 2, 3
def __exit__(self, t, v, tb): pass
targets = {1: [0, 1, 2]}
with C() as (targets[1][0], targets[1][1], targets[1][2]):
self.assertEqual(targets, {1: [1, 2, 3]})
with C() as (list(targets.values())[0][2], list(targets.values())[0][1], list(targets.values())[0][0]):
self.assertEqual(targets, {1: [3, 2, 1]})
with C() as (targets[1], targets[2], targets[3]):
self.assertEqual(targets, {1: 1, 2: 2, 3: 3})
class B: pass
blah = B()
with C() as (blah.one, blah.two, blah.three):
self.assertEqual(blah.one, 1)
self.assertEqual(blah.two, 2)
self.assertEqual(blah.three, 3)
class ExitSwallowsExceptionTestCase(unittest.TestCase):
def testExitTrueSwallowsException(self):
class AfricanSwallow:
def __enter__(self): pass
def __exit__(self, t, v, tb): return True
try:
with AfricanSwallow():
1/0
except ZeroDivisionError:
self.fail("ZeroDivisionError should have been swallowed")
def testExitFalseDoesntSwallowException(self):
class EuropeanSwallow:
def __enter__(self): pass
def __exit__(self, t, v, tb): return False
try:
with EuropeanSwallow():
1/0
except ZeroDivisionError:
pass
else:
self.fail("ZeroDivisionError should have been raised")
def test_main():
run_unittest(FailureTestCase, NonexceptionalTestCase,
NestedNonexceptionalTestCase, ExceptionalTestCase,
NonLocalFlowControlTestCase,
AssignmentTargetTestCase,
ExitSwallowsExceptionTestCase)
if __name__ == '__main__':
test_main()