Re: BUG: Various "advice.*" config doesn't work

From: Taylor Blau <me@ttaylorr.com>
Date: Jan 31, 2022, 17:34 UTC
Message-ID: <YfgdsnfQ05ywre8l@nand.local>
In-Reply-To: <xmqq1r0nke71.fsf@gitster.g>

On Mon, Jan 31, 2022 at 09:28:02AM -0800, Junio C Hamano wrote:

Show 18 quoted lines

> Taylor Blau <me@ttaylorr.com> writes:
>
> > But having something like (in builtin/add.c:add_files()):
> >
> >     if (advice_enabled(ADVICE_ADD_IGNORED_FILES))
> >         advise(_("..."));
> >
> > feels like it opens the door to call advise() by default if we happened
> > to forget to read the configuration.
>
> True.
>
> > I think that is a good candidate to
> > be replaced with advice_if_enabled().
>
> Meaning advice_enabled() will lazily load the configuration?  If so,
> then what you saw in builtin/add.c::add_files() would automatically
> become just as safe as advice_if_enabled(), no?

The change I was wondering aloud about was having advice_enabled() lazily load the configuration.

So what is written in add_files() above would become safe (if it wasn't already), and could easily be replaced with advise_if_enabled().

Show 21 quoted lines

> > I'm not sure if that is true in general, though. Take a look at this
> > example (from branch.c:create_branch()):
> >
> >     if (advice_enabled(ADVICE_SET_UPSTREAM_FAILURE)) {
> >         error(_(upstream_missing), start_name);
> >         advise(_(upstream_advice));
> >         exit(1);
> >     }
> >     die(_(upstream_missing), start_name);
> >
> > This also makes it possible to call advise() when we shouldn't have. But
> > how should we rewrite this code? Wanting to either error() (and then
> > call exit(1)) or die() based on whether or not we're going to print the
> > advice makes it tricky.
>
> I am puzzled why you think the above "check, do things, give a
> piece of advice, and do even more things" needs to be rewritten.
>
> Everything you are showing above becomes a problem only when
> advice_enabled() does not work reliably, due to a bug that fails to
> read the configuration.

What I'm more or less trying to point out is that an unguarded advise() function defeats the purpose of the advice API, which should exist to avoid mistakes like these (where advice is printed to the user when they have already opted out of that advice).

I was thinking that it would be nice to have advise() take an advice_type enum and have it behave like advise_if_enabled(). But there are spots that you really do want to print advice unconditionally. And that spot in create_branch() is one of those where it isn't clear that the change I'm proposing works.

(BTW, I would definitely disagree that I'm saying anything "needs" to be rewritten here. This is all just thinking aloud about what the advice API can and should help callers with.)

Show 8 quoted lines

> > Maybe, though I still think BUG() is a bit extreme, and we could
> > accomplish the same by having the advice API just read the config if it
> > hasn't done so already before emitting advice.
>
> Calling things like git_config(git_default_config) with side-effects
> on other global variables are definitely a no-no, but as long as it
> reacts to configuration variables only under advice.* namespace,
> that might be OK.

Yes, I definitely agree we should absolutely not be calling git_default_config() as part of "lazily load the advice.* configuration".

> Thanks.

Thanks, Taylor