Re: [PATCH] completion: do not cache if --git-completion-helper fails

From: Duy Nguyen <pclouds@gmail.com>
To: Felipe Contreras <felipe.contreras@gmail.com>
Cc: "SZEDER Gábor" <szeder.dev@gmail.com>, Git <git@vger.kernel.org>,
	"Junio C Hamano" <gitster@pobox.com>
Subject: Re: [PATCH] completion: do not cache if --git-completion-helper fails
Date: Wed, 12 Jun 2019 15:52:19 +0700	[thread overview]
Message-ID: <CACsJy8CGtZMn0aa7QRj7Dz-jZS2K2fviUJ_Lii48FRY4E84i5Q@mail.gmail.com> (raw)
In-Reply-To: <CAMP44s3EsNzBtt_pG8HVp_RTMTTArk7Twhty4_tzf2iiZ7TKUQ@mail.gmail.com>

On Sat, Jun 8, 2019 at 12:33 AM Felipe Contreras
<felipe.contreras@gmail.com> wrote:
>
> On Fri, Jun 7, 2019 at 5:02 AM SZEDER Gábor <szeder.dev@gmail.com> wrote:
> >
> > On Fri, Jun 07, 2019 at 04:30:34PM +0700, Nguyễn Thái Ngọc Duy wrote:
> > > "git <cmd> --git-completion-helper" could fail if the command checks for
> > > a repo before parse_options(). If the result is cached, later on when
> > > the user moves to a worktree with repo, tab completion will still fail.
> > >
> > > Avoid this by detecting errors and not cache the completion output. We
> > > can try again and hopefully succeed next time (e.g. when a repo is
> > > found).
> > >
> > > Of course if --git-completion-helper fails permanently because of other
> > > reasons (*), this will slow down completion. But I don't see any better
> > > option to handle that case.
> >
> > I think a permanently failing 'git cmd --git-completion-helper'
> > shouldn't really happen, unless there is a bug in the completion
> > script or the git installation or similar exceptional situation.  And
> > then that issue should be fixed, but I don't think we should worry
> > about an extra subshell and git process in those situations.
>
> Indeed. In think there's only sane option to make this work in all
> situation; a reorganization.
>
> Something like this should work:
>
> struct command checkout_command = {
> .name = "checkout",
> .function = cmd_checkout,
> .run_options = RUN_SETUP | NEED_WORK_TREE,
> .help = N_("Switch branches or restore working tree files"),
> .options = {
> OPT__QUIET(&opts.quiet, N_("suppress progress reporting")),
> ...
> },
> }
>
> This way we could run parse_options_show_gitcomp() from git.c and not
> worry about whatever cmd_checkout() needs.

This only works for a few commands. Those with subcommands already
have struct option[] array scattered in different places. And some new
ones also have struct option array dynamically created.

It's not impossible to do. But I feel there's a lot of reorganizing
for little gain. Maybe when we pass 'struct repository *' to all
commands, which means we hit all commmands at once anyway, we can
reconsider this (and having config parser in a more declarative form
like cmd option parser).

> This has the added advantage that it gathers information about this
> command that is stray in multiple sources (git.c, command-list.h), and
> it makes builtin.h cleaner too.
>
> Plus, we could rework the way -h works too.
-- 
Duy