LockFile.acquire() argument docs are incorrect

[Kirk Strauser]

According to http://pythonhosted.org/lockfile/lockfile.html#lockfile.LockFile.acquire:

> If the timeout is zero or a negative number the AlreadyLocked exception will be raised if the file is currently locked by another process or thread.

I have two Python shells open. In one, I've run:

>>> import lockfile
>>> a = lockfile.LockFile('/tmp/locker')
>>> a.acquire()

In the other, I run:

>>> import lockfile
>>> a = lockfile.LockFile('/tmp/locker')
>>> a.acquire(0) # Hangs until I ctrl-C interrupt it
>>> a.acquire(-1)
Traceback (most recent call last):
[...]
lockfile.AlreadyLocked: /tmp/locker is already locked

The docs incorrectly state that a.acquire(0) and a.acquire(-1) should have the same behavior.

[Michael Komitee (mkomitee)]

I just opened https://bugs.launchpad.net/pylockfile/+bug/1468124 before I realized it was more or less a duplicate of this issue.

I would add that this was noted and the current code looks like an attempt to fix the bug:

>>> % git show 58c3832d --pretty=full
>>> commit 58c3832
>>> Author: Skip Montanaro <email address hidden>
>>> Commit: Skip Montanaro <email address hidden>
>>>
>>> fix for timeout=0
>>>
>>> diff --git a/lockfile/linklockfile.py b/lockfile/linklockfile.py
>>> index a906568..9c50673 100644
>>> --- a/lockfile/linklockfile.py
>>> +++ b/lockfile/linklockfile.py
>>> @@ -19,7 +19,7 @@ class LinkLockFile(LockBase):
>>> except IOError:
>>> raise LockFailed("failed to create %s" % self.unique_name)
>>>
>>> - timeout = timeout or self.timeout
>>> + timeout = timeout is not None and timeout or self.timeout
>>> end_time = time.time()
>>> if timeout is not None and timeout > 0:
>>> end_time += timeout
>>> *SNIP*

I'd also mention that this is a regression introduced by ecd17a7, and so it would probably be better to fix the code than the docs.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/221100
Committed: https://git.openstack.org/cgit/openstack/pylockfile/commit/?id=333cbd39a50e5908136f9270a354ff5d1f6b6956
Submitter: Jenkins
Branch: master

commit 333cbd39a50e5908136f9270a354ff5d1f6b6956
Author: Davanum Srinivas <email address hidden>
Date: Mon Sep 7 16:05:56 2015 -0400

    lockfile.acquire doesn't accept a timeout of 0

    Docs indicates that lock.acquire(timeout=0) would not block, but it
    does (for linklockfile) because 0 is not truthy, and the line:

       timeout = timeout is not None and timeout or self.timeout

    when timeout is 0 causes it to default to self.timeout, which by default is None.

    So rewrite the condition better to take into account that timeout may
    be set to 0.

    Closes-Bug: #1468124
    Closes-Bug: #1419127
    Change-Id: Idf0d00977e79661e1eafd695d6e148e5f27e1840