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bpo-30028: make test.support.temp_cwd() fork-safe #1066

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Merged
merged 8 commits into from
Feb 23, 2018
Merged

bpo-30028: make test.support.temp_cwd() fork-safe #1066

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22e032a
bpo-30028: make test.support.temp_cwd() fork-safe
Apr 9, 2017
7b96cf7
Update test_regrtest.py
Apr 10, 2017
9ca9665
bpo-30028: Add comments, move the test to test_support.py
Apr 10, 2017
1a0364d
bpo-30028: Run the fork test as an external script.
Apr 10, 2017
0f480d9
bpo-30028: replace assert by if ...: raise AssertionError
Apr 15, 2017
8cebac8
bpo-30028: improve the test case
Apr 22, 2017
1b78826
Merge branch 'master' into tempcwd_fork_fix
serhiy-storchaka Feb 21, 2018
ee34a5b
bpo-30028: Add name to Misc/ACKS
Feb 22, 2018
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6 changes: 5 additions & 1 deletion Lib/test/support/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -960,10 +960,14 @@ def temp_dir(path=None, quiet=False):
warnings.warn(f'tests may fail, unable to create '
f'temporary directory {path!r}: {exc}',
RuntimeWarning, stacklevel=3)
if dir_created:
pid = os.getpid()
try:
yield path
finally:
if dir_created:
# In case the process forks, let only the parent remove the
# directory. The child has a diffent process id. (bpo-30028)
if dir_created and pid == os.getpid():
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The test is non obvious, can you please add a short comment explaining why you test the pid?

I guess that it's test to avoid that two processes try to remove the directory if the parent uses fork()?

Add bpo-30028 in the comment.

rmtree(path)

@contextlib.contextmanager
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18 changes: 18 additions & 0 deletions Lib/test/test_support.py
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Expand Up @@ -7,7 +7,9 @@
import socket
import tempfile
import errno
import textwrap
from test import support
from test.support import script_helper

TESTFN = support.TESTFN

Expand Down Expand Up @@ -161,6 +163,22 @@ def test_temp_dir__existing_dir__quiet_true(self):
f'temporary directory {path!r}: '),
warn)

@unittest.skipUnless(hasattr(os, "fork"), "test requires os.fork")
def test_temp_dir__forked_child(self):
"""Test that a forked child process does not remove the directory."""
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Please add a reference to the issue: bpo-30028

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No other doc string in this file contains a reference to bpo. Therefore I added the reference as a comment.

# Run the test as an external script, because it uses fork.
script_helper.assert_python_ok("-c", textwrap.dedent("""
import os
from test import support
with support.temp_cwd() as temp_path:
pid = os.fork()
if pid != 0:
# parent process
os.waitpid(pid, 0) # wait for the child to terminate
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Please test that the child didn't fail.

# make sure that temp_path is still present
assert os.path.isdir(temp_path), "Child removed temp_path."
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I would avoid assert keyword which might be removed depending on the Python option, but use an explicit if + raise Exception(...). But maybe it's ok, I don't know :-)

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Since this is a subprocess, explicit os.exit() can be more appropriate.

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I'm currently on a business trip and can't access my Linux box. I'll update the pull request on Thursday. But could you please agree on either raising AssertionError or a print() and explicit os.exit(). In the end it makes no difference.

"""))
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Please add a comment explaining that the child exits without removing the temporary directory.

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Isn't the comment above enough?


# Tests for change_cwd()

def test_change_cwd(self):
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