Re: [PATCH v4] add-patch: response to unknown command

[Rubén Justo <rjusto@xxxxxxxxx>]

On Wed, Apr 24, 2024 at 09:44:32PM -0400, Jeff King wrote:
> On Sun, Apr 21, 2024 at 11:52:33PM +0200, Rubén Justo wrote:
> 
> > +test_expect_success 'unknown command' '
> > +	test_when_finished "git reset --hard; rm -f command" &&
> > +	echo W >command &&
> > +	git add -N command &&
> > +	git diff command >expect &&
> > +	cat >>expect <<-EOF &&
> > +	(1/1) Stage addition [y,n,q,a,d,e,p,?]? Unknown command ${SQ}W${SQ} (use ${SQ}?${SQ} for help)
> > +	(1/1) Stage addition [y,n,q,a,d,e,p,?]?$SP
> > +	EOF
> > +	git add -p -- command <command >actual 2>&1 &&
> > +	test_cmp expect actual
> > +'
> 
> I got a test failure on Windows CI from this.

Thank you for testing thoroughly.

> The test_cmp output looks
> like this:
> 
>   -(1/1) Stage addition [y,n,q,a,d,e,p,?]? Unknown command 'W' (use '?' for help)
>   -(1/1) Stage addition [y,n,q,a,d,e,p,?]?
>   +(1/1) Stage addition [y,n,q,a,d,e,p,?]? (1/1) Stage addition [y,n,q,a,d,e,p,?]?
>   +Unknown command 'W' (use '?' for help)
> 
> which makes me suspect a race. Perhaps because the prompt is going to
> stdout, but the "Unknown command" message goes to stderr?

I have to read the thread pointed by Eric, but my knee-jerk reaction has
been to think in something like:

diff --git a/add-patch.c b/add-patch.c
index 447e8166d2..0090543f89 100644
--- a/add-patch.c
+++ b/add-patch.c
@@ -292,6 +292,7 @@ static void err(struct add_p_state *s, const char *fmt, ...)
 {
        va_list args;

        va_start(args, fmt);
+       fflush(stdout);
        fputs(s->s.error_color, stderr);
        vfprintf(stderr, fmt, args);