Am 14.04.2020 um 22:13 hat Markus Armbruster geschrieben: > Kevin Wolf <kw...@redhat.com> writes: > > > Am 14.04.2020 um 15:36 hat Markus Armbruster geschrieben: > >> Kevin Wolf <kw...@redhat.com> writes: > >> > Am 14.04.2020 um 11:10 hat Markus Armbruster geschrieben: > >> >> Eric Blake <ebl...@redhat.com> writes: > >> >> > On 4/9/20 10:30 AM, Markus Armbruster wrote: > >> >> >> + { "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? > >> > >> Of course we should consider reasonable user expectations. > >> > >> Grumpy aside: when I do, I commonly run into objections that users > >> reasonably expect things not to change. > > > > Fair point. It's not always easy to tell whether something should be > > considered a bug in the external interface (and consequently be fixed) > > or just an idiosyncrasy that people may have get used to (and therefore > > requires deprecation before improving it). > > > > In this specific case, I'm not aware of empty option names actually > > doing anything useful anywhere, so I think it might be clearer in this > > case that it's indeed a bug. > > You're right in that backward compatibility is not a convincing argument > for stuff that has no known productive uses, and is bonkers to boot. > > >> > 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. > >> > >> My preferred way to address QemuOpts parsing madness is replacing it > >> wholesale by keyval.c, but that's some time off, I'm afraid. > >> > >> This series merely aims for more method to the same old madness. > > > > I understand. Though I think replacing with keyval will be potentially > > less problematic if QemuOpts already behaved more similar. > > > > If I were writing the code, I think I would use existing bugs and > > inconsistencies as an excuse to make QemuOpts behave more like what > > keyval can easily handle by declaring whatever is closest to keyval as > > the correct interpretation. > > Fair enough. > > However, > > (1) is_valid_option_list()'s and opts_do_parse()'s parse of "a,b,,help" > are equidistant from keyval_parse()'s: > > opts_do_parse() splits it into four parts: > > "a" (desugared to a=on) > "b" (desugared to b=on) > "" (desugared to =on) > "help" (desugared to help=on) > > has_help_option() splits it into two: > > "a" > "b,help" > > keyval_parse() fails: > > Expected '=' after parameter 'a' > > If I it implemented boolean sugar, then it would fail at the third > comma, just like ",help" fails now: > > Invalid parameter '' > > Fails because ",help" does not start with a valid name. > > Thus, the answer to the question which of the two functions covered > by the test are wrong would be "both".
opts_do_parse() can return an error. So maybe what we should do is rejecting empty option names there? > (2) This series tries hard not to write QemuOpts parsing code. It > throws away QemuOpts parsing code. Arguably, an additional error is writing QemuOpts parsing code, but maybe little enough that it's tolerable? Kevin