bpo-30197: Enhance functions swap_attr() and swap_item() in test.support. (#1341)

* bpo-30197: Enhance functions swap_attr() and swap_item() in test.support.

They now work when delete replaced attribute or item inside the with
statement.  The old value of the attribute or item (or None if it doesn't
exist) now will be assigned to the target of the "as" clause, if there is
one.

* Update docstrings.
This commit is contained in:
Serhiy Storchaka 2017-04-28 19:17:26 +03:00 committed by Victor Stinner
parent 80a3da4d4a
commit d1a1def7bf
4 changed files with 43 additions and 13 deletions

View File

@ -2119,12 +2119,15 @@ def swap_attr(obj, attr, new_val):
restoring the old value at the end of the block. If `attr` doesn't
exist on `obj`, it will be created and then deleted at the end of the
block.
The old value (or None if it doesn't exist) will be assigned to the
target of the "as" clause, if there is one.
"""
if hasattr(obj, attr):
real_val = getattr(obj, attr)
setattr(obj, attr, new_val)
try:
yield
yield real_val
finally:
setattr(obj, attr, real_val)
else:
@ -2132,7 +2135,8 @@ def swap_attr(obj, attr, new_val):
try:
yield
finally:
delattr(obj, attr)
if hasattr(obj, attr):
delattr(obj, attr)
@contextlib.contextmanager
def swap_item(obj, item, new_val):
@ -2146,12 +2150,15 @@ def swap_item(obj, item, new_val):
restoring the old value at the end of the block. If `item` doesn't
exist on `obj`, it will be created and then deleted at the end of the
block.
The old value (or None if it doesn't exist) will be assigned to the
target of the "as" clause, if there is one.
"""
if item in obj:
real_val = obj[item]
obj[item] = new_val
try:
yield
yield real_val
finally:
obj[item] = real_val
else:
@ -2159,7 +2166,8 @@ def swap_item(obj, item, new_val):
try:
yield
finally:
del obj[item]
if item in obj:
del obj[item]
def strip_python_stderr(stderr):
"""Strip the stderr of a Python process from potential debug output

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@ -295,17 +295,34 @@ class TestSupport(unittest.TestCase):
def test_swap_attr(self):
class Obj:
x = 1
pass
obj = Obj()
with support.swap_attr(obj, "x", 5):
obj.x = 1
with support.swap_attr(obj, "x", 5) as x:
self.assertEqual(obj.x, 5)
self.assertEqual(x, 1)
self.assertEqual(obj.x, 1)
with support.swap_attr(obj, "y", 5) as y:
self.assertEqual(obj.y, 5)
self.assertIsNone(y)
self.assertFalse(hasattr(obj, 'y'))
with support.swap_attr(obj, "y", 5):
del obj.y
self.assertFalse(hasattr(obj, 'y'))
def test_swap_item(self):
D = {"item":1}
with support.swap_item(D, "item", 5):
self.assertEqual(D["item"], 5)
self.assertEqual(D["item"], 1)
D = {"x":1}
with support.swap_item(D, "x", 5) as x:
self.assertEqual(D["x"], 5)
self.assertEqual(x, 1)
self.assertEqual(D["x"], 1)
with support.swap_item(D, "y", 5) as y:
self.assertEqual(D["y"], 5)
self.assertIsNone(y)
self.assertNotIn("y", D)
with support.swap_item(D, "y", 5):
del D["y"]
self.assertNotIn("y", D)
class RefClass:
attribute1 = None

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@ -273,13 +273,12 @@ class TestGetDefaultTempdir(BaseTestCase):
tempfile._get_default_tempdir()
self.assertEqual(os.listdir(our_temp_directory), [])
open = io.open
def bad_writer(*args, **kwargs):
fp = open(*args, **kwargs)
fp = orig_open(*args, **kwargs)
fp.write = raise_OSError
return fp
with support.swap_attr(io, "open", bad_writer):
with support.swap_attr(io, "open", bad_writer) as orig_open:
# test again with failing write()
with self.assertRaises(FileNotFoundError):
tempfile._get_default_tempdir()

View File

@ -1107,6 +1107,12 @@ Tools/Demos
Tests
-----
- bpo-30197: Enhanced functions swap_attr() and swap_item() in the
test.support module. They now work when delete replaced attribute or item
inside the with statement. The old value of the attribute or item (or None
if it doesn't exist) now will be assigned to the target of the "as" clause,
if there is one.
- Issue #24932: Use proper command line parsing in _testembed
- Issue #28950: Disallow -j0 to be combined with -T/-l in regrtest