[Koha-devel] Conventions for CLI scripts

[Paul Poulain]

Le 18/09/2014 03:51, Robin Sheat a écrit :
> There's been talk of making a few conventions for the parameters to
> command-line scripts.
(a little bit late answer...)

I've 2 strong opinions:
   * if the script does something that can't be rolled back, there 
*must* be a of validation. for example "delete_bibs_without_items.pl" 
must not delete anything without warning. This warning can be something 
like "you're about to delete 100000 bibliographic records. Are you sure 
Y/N", unless the script is run with a parameter 
(delete_bibs_without_items.pl -y)
   * we must choose an option, and make it valid for all scripts.


Outside from those 2 things, I've no preference. I tend to be on Owen 
side : no parameter = small help -ie: explicit parameter needed to run 
the script)

Additional question: some CLI are made for being run from cron. In this 
case, no information should be printed unless something goes wrong. SO: 
by default, should scripts be silent:
  * no parameters = silent mode
  * -v = some informations
  * -vv (or -v 2, or --very-verbose, I don't care ;-) ) = verbose mode

  or should there be an explicit "silent mode":
  * -s parameter = silent mode
  * no parameter = some informations
  * -v = verbose mode

something for a future technical meeting and improved coding guidelines ?
>
> The initial discussion was dealing with "test mode" where it runs
> through all the actions but doesn't actually do anything, i.e. you know
> if it'll complete successfully.
>
>       1. There are two directions for this:
>               I. By default the action will be performed, unless you add
>                  an argument (--dry-run for example.)
>              II. By default the action will not be performed, unless you
>                  add an argument (--commit for example.)
>       2. What do we want to call the options, whichever way is picked?
>               I. Keeping in mind that some things (-c for example) can
>                  conflict with other conventions.
>       3. Are there any other conventions we should deal with at the same
>          time?
>
> While I have your attention, we should be more careful about how the dry
> run stuff is actually done. I've found one script that gives you a
> different count if you're in dry run mode (e.g. it'll say "0 actions
> done") which is strictly correct, but means you don't know if it's 0
> because something's wrong, or because it's in dry run mode. Unless
> there's a good reason, it's best to do everything in a commit, so
> something like:
>
>          $dbi->begin_work;
>          ...do stuff...
>          print "$count actions done.\n";
>          if ($dry_run) {
>          	$dbi->rollback;
>          	print "Changes NOT committed.\n";
>          } else {
>          	$dbi->commit;
>          }
>
> This also has the side effect that if your program crashes in any mode,
> you're not left with an inconsistent result. But mostly it means
> that /everything/ will happen in exactly the same way no matter what,
> except the results just won't be saved.
>
>
>
>
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-- 
Paul Poulain, Associé-gérant / co-owner
BibLibre, expert du logiciel libre pour les bibliothèques
BibLibre, Open Source software for libraries expert