bug#66993: [PATCH] project.el: avoid asking user about project-list-file lock

[Spencer Baugh]

Eli Zaretskii <eliz@gnu.org> writes:
>> Date: Wed, 8 Nov 2023 15:56:11 +0200
>> Cc: sbaugh@janestreet.com, 66993@debbugs.gnu.org
>> From: Dmitry Gutov <dmitry@gutov.dev>
>> 
>> On 08/11/2023 15:50, Eli Zaretskii wrote:
>> > Why do you need an error when you can use file-locked-p to check up
>> > front that the file is locked?
>> 
>> IIUC the problem comes due to concurrent writes from concurrent writes 
>> from parallel Emacs instances.
>> 
>> Simply checking whether the file is locked before writing, without 
>> trying to obtain the lock, is unlikely to be a reliable solution 
>> (another instance might lock it right after we checked).
>> 
>> Anyway, these writes must be very fast and relatively infrequent. So I'm 
>> surprised that this has came up, personally.
>
> If that's the case, just catch the error and retry, several times,
> perhaps with variable delays.

Perhaps, but it would be nice to do that by catching specifically
file-locked rather than catching all errors.  Which is something which
can't be done right now, other than with the cl-flet approach in my
original approach.