Re: [PATCH for-5.1 1/8] tests-qemu-opts: Cover has_help_option(), qemu_opt_has_help_opt()

[Kevin Wolf <kwolf@redhat.com>]

Am 14.04.2020 um 11:10 hat Markus Armbruster geschrieben:
> Eric Blake <eblake@redhat.com> writes:
> 
> > On 4/9/20 10:30 AM, Markus Armbruster wrote:
> >> The two turn out to be inconsistent for "a,b,,help".  Test case
> >> marked /* BUG */.
> >>
> >> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> >> ---
> >>   tests/test-qemu-opts.c | 38 ++++++++++++++++++++++++++++++++++++++
> >>   1 file changed, 38 insertions(+)
> >>
> >
> >> +static void test_has_help_option(void)
> >> +{
> >> +    static const struct {
> >> +        const char *params;
> >> +        /* expected value of has_help_option() */
> >> +        bool expect_has_help_option;
> >> +        /* expected value of qemu_opt_has_help_opt() with implied=false */
> >> +        bool expect_opt_has_help_opt;
> >> +        /* expected value of qemu_opt_has_help_opt() with implied=true */
> >> +        bool expect_opt_has_help_opt_implied;
> >> +    } test[] = {
> >> +        { "help", true, true, false },

While we're talking about unintuitive, I feel the result for
implied=true is confusing, too. Never noticed it before, but are we
really sure that it is the best possible behaviour that '-chardev help'
and '-chardev id=foo,help' print two entirely different help texts?

I'm not requesting to change anything about this in this series, but
just making the point that maybe sometimes the existing behaviour is
questionable.

> >> +        { "helpme", false, false, false },
> >> +        { "a,help", true, true, true },
> >> +        { "a=0,help,b", true, true, true },
> >> +        { "help,b=1", true, true, false },
> >> +        { "a,b,,help", false /* BUG */, true, true },
> >
> > So which way are you calling the bug?  Without looking at the code but
> > going off my intuition, I parse this as option 'a' and option
> > 'b,help'. The latter is not a normal option name because it contains a
> > ',', but is a valid option value.
> >
> > I agree that we have a bug, but I'm not yet sure in which direction
> > the bug lies (should has_help_option be fixed to report true, in which
> > case the substring ",help" has precedence over ',,' escaping; or
> > should qemu_opt_has_help_opt be fixed to report false, due to treating
> > 'b,help' after ',,' escape removal as an invalid option name).  So the
> > placement of the /* BUG */ comment matters - where you placed it, I'm
> > presuming that later in the series you change has_help_option to
> > return true, even though that goes against my intuitive parse.
> 
> In addition to the canonical QemuOpts parser opts_do_parse(), we have
> several more, and of course they all differ from the canonical one for
> corner cases.
> 
> I treat the canonical one as correct, and fix the others by eliminating
> the extra parsers.
> 
> The others are:
> 
> * has_help_option()
> 
>   Fixed in PATCH 5 by reusing the guts of opts_do_parse().
> 
> * is_valid_option_list()
> 
>   Fixed in PATCH 8 by not parsing.
> 
> * "id" extraction in opts_parse()
> 
>   Lazy hack.  Fixed in PATCH 3 by reusing the guts of opts_do_parse().
> 
> Back to your question: the value of has_help_option() differs from the
> value of qemu_opt_has_help_opt().  The latter uses the canonical parser,
> the former is one of the other parsers.  I therefore judge the latter
> right and the former wrong.

Shouldn't we also consider what users would reasonably expect?

Getting it parsed as an empty option name (I assume with a default value
of "on"?) certainly looks like something that would surprise most users
and, as you can see, even some QEMU developers.

Kevin