Eli Zaretskii <eliz@gnu.org> writes:
>> From: Spencer Baugh <sbaugh@janestreet.com>
>> Cc: dmitry@gutov.dev,  66993@debbugs.gnu.org
>> Date: Thu, 09 Nov 2023 13:01:09 -0500
>> 
>> Eli Zaretskii <eliz@gnu.org> writes:
>> > Please show the result of this change on what Emacs prints in batch
>> > mode when this error is signaled.
>> 
>> Before:
>> 
>> $ ./src/emacs -Q --batch --eval '(write-region "foo" nil "~/file")'
>> /home/sbaugh/file locked by sbaugh@igm-qw... (pid 3781848): (s, q, p, ?)? 
>> 
>> Error: error ("Cannot resolve lock conflict in batch mode")
>>   mapbacktrace(#f(compiled-function (evald func args flags) #<bytecode 0x957865a77aef0ee>))
>>   debug-early-backtrace()
>>   debug-early(error (error "Cannot resolve lock conflict in batch mode"))
>>   signal(error ("Cannot resolve lock conflict in batch mode"))
>>   error("Cannot resolve lock conflict in batch mode")
>>   ask-user-about-lock("/home/sbaugh/file" "sbaugh@igm-qws-u22796a (pid 3781848)")
>>   write-region("foo" nil "~/file")
>>   eval((write-region "foo" nil "~/file") t)
>>   command-line-1(("--eval" "(write-region \"foo\" nil \"~/file\")"))
>>   command-line()
>>   normal-top-level()
>> Cannot resolve lock conflict in batch mode
>> 
>> 
>> After:
>> 
>> $ ./src/emacs -Q --batch --eval '(write-region "foo" nil "~/file")'
>> /home/sbaugh/file locked by sbaugh@igm-qw... (pid 3781848): (s, q, p, ?)? 
>> 
>> Error: file-locked ("/home/sbaugh/file" "sbaugh@igm-qws-u22796a (pid 3781848)")
>>   mapbacktrace(#f(compiled-function (evald func args flags) #<bytecode 0x179d0e5a77aef0e7>))
>>   debug-early-backtrace()
>>   debug-early(error (file-locked "/home/sbaugh/file" "sbaugh@igm-qws-u22796a (pid 3781848)"))
>>   signal(file-locked ("/home/sbaugh/file" "sbaugh@igm-qws-u22796a (pid 3781848)"))
>>   ask-user-about-lock("/home/sbaugh/file" "sbaugh@igm-qws-u22796a (pid 3781848)")
>>   write-region("foo" nil "~/file")
>>   eval((write-region "foo" nil "~/file") t)
>>   command-line-1(("--eval" "(write-region \"foo\" nil \"~/file\")"))
>>   command-line()
>>   normal-top-level()
>> /home/sbaugh/file: sbaugh@igm-qws-u22796a (pid 3781848)
>
> Thanks, that's what I thought: this loses information.  The "Cannot
> resolve lock conflict in batch mode" part is important, since it
> explains the "file-locked" part.  So please include the missing text
> in the list passed to 'signal' as its DATA argument, so as not to lose
> this explanation.

OK, how about this?  Which makes Emacs print:

Error: file-locked ("/home/sbaugh/file" "sbaugh@earth (pid 1852838)" "Cannot resolve lock conflict in batch mode")
  mapbacktrace(#f(compiled-function (evald func args flags) #<bytecode -0x1f22147a251783b>))
  debug-early-backtrace()
  debug-early(error (file-locked "/home/sbaugh/file" "sbaugh@earth (pid 1852838)" "Cannot resolve lock conflict in batch mode"))
  signal(file-locked ("/home/sbaugh/file" "sbaugh@earth (pid 1852838)" "Cannot resolve lock conflict in batch mode"))
  ask-user-about-lock("/home/sbaugh/file" "sbaugh@earth (pid 1852838)")
  write-region("foo" nil "~/file")
  eval((write-region "foo" nil "~/file") t)
  command-line-1(("--eval" "(write-region \"foo\" nil \"~/file\")"))
  command-line()
  normal-top-level()
/home/sbaugh/file: sbaugh@earth (pid 1852838), Cannot resolve lock conflict in batch mode