PEP 343 -- the with-statement.
This was started by Mike Bland and completed by Guido
(with help from Neal).
This still needs a __future__ statement added;
Thomas is working on Michael's patch for that aspect.
There's a small amount of code cleanup and refactoring
in ast.c, compile.c and ceval.c (I fixed the lltrace
behavior when EXT_POP is used -- however I had to make
lltrace a static global).
diff --git a/Lib/test/test_with.py b/Lib/test/test_with.py
new file mode 100644
index 0000000..9d809ef
--- /dev/null
+++ b/Lib/test/test_with.py
@@ -0,0 +1,560 @@
+#!/usr/bin/env python
+
+"""Unit tests for the with statement specified in PEP 343."""
+
+__author__ = "Mike Bland"
+__email__ = "mbland at acm dot org"
+
+import unittest
+from test.contextmanager import GeneratorContextManager
+from test.nested import nested
+from test.test_support import run_unittest
+
+
+class MockContextManager(GeneratorContextManager):
+ def __init__(self, gen):
+ GeneratorContextManager.__init__(self, gen)
+ self.context_called = False
+ self.enter_called = False
+ self.exit_called = False
+ self.exit_args = None
+
+ def __context__(self):
+ self.context_called = True
+ return GeneratorContextManager.__context__(self)
+
+ 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 MockNested(nested):
+ def __init__(self, *contexts):
+ nested.__init__(self, *contexts)
+ self.context_called = False
+ self.enter_called = False
+ self.exit_called = False
+ self.exit_args = None
+
+ def __context__(self):
+ self.context_called = True
+ return nested.__context__(self)
+
+ 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 testContextAttributeError(self):
+ class LacksContext(object):
+ def __enter__(self):
+ pass
+
+ def __exit__(self, type, value, traceback):
+ pass
+
+ def fooLacksContext():
+ foo = LacksContext()
+ with foo: pass
+ self.assertRaises(AttributeError, fooLacksContext)
+
+ def testEnterAttributeError(self):
+ class LacksEnter(object):
+ def __context__(self):
+ pass
+
+ 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 __context__(self):
+ pass
+
+ 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 testContextThrows(self):
+ class ContextThrows(object):
+ def __context__(self):
+ raise RuntimeError("Context threw")
+
+ def shouldThrow():
+ ct = ContextThrows()
+ self.foo = None
+ with ct as self.foo:
+ pass
+ self.assertRaises(RuntimeError, shouldThrow)
+ self.assertEqual(self.foo, None)
+
+ def testEnterThrows(self):
+ class EnterThrows(object):
+ def __context__(self):
+ return self
+
+ def __enter__(self):
+ raise RuntimeError("Context 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 __context__(self):
+ return self
+ def __enter__(self):
+ return
+ def __exit__(self, *args):
+ raise RuntimeError(42)
+ def shouldThrow():
+ with ExitThrows():
+ pass
+ self.assertRaises(RuntimeError, shouldThrow)
+
+class ContextmanagerAssertionMixin(object):
+ TEST_EXCEPTION = RuntimeError("test exception")
+
+ def assertInWithManagerInvariants(self, mock_manager):
+ self.assertTrue(mock_manager.context_called)
+ 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.context_called)
+ 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.context_called)
+ 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.
+ # FIXME: what should this do: with nested(m) as (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(unittest.TestCase, ContextmanagerAssertionMixin):
+ 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.context_called)
+ 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)
+
+
+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(targets.keys(), [1])
+ self.assertEqual(targets[1][0].__class__, MockResource)
+ with mock_contextmanager_generator() as targets.values()[0][1]:
+ self.assertEqual(targets.keys(), [1])
+ self.assertEqual(targets[1][1].__class__, MockResource)
+ with mock_contextmanager_generator() as targets[2]:
+ keys = 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 __context__(self): return self
+ def __enter__(self): return 1, 2, 3
+ def __exit__(self, *a): 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 (targets.values()[0][2], targets.values()[0][1], 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)
+
+
+def test_main():
+ run_unittest(FailureTestCase, NonexceptionalTestCase,
+ NestedNonexceptionalTestCase, ExceptionalTestCase,
+ NonLocalFlowControlTestCase,
+ AssignmentTargetTestCase)
+
+
+if __name__ == '__main__':
+ test_main()