Re: [PATCH v7 06/13] qmp: Call monitor_set_cur() only in qmp_dispatch()

[Dr. David Alan Gilbert]

* Kevin Wolf (kwolf@redhat.com) wrote:
> Am 30.09.2020 um 15:14 hat Markus Armbruster geschrieben:
> > Kevin Wolf <kwolf@redhat.com> writes:
> > 
> > > Am 30.09.2020 um 11:26 hat Markus Armbruster geschrieben:
> > >> Kevin Wolf <kwolf@redhat.com> writes:
> > >> 
> > >> > Am 28.09.2020 um 13:42 hat Markus Armbruster geschrieben:
> > >> >> Kevin Wolf <kwolf@redhat.com> writes:
> > >> >> 
> > >> >> > Am 14.09.2020 um 17:10 hat Markus Armbruster geschrieben:
> > >> >> >> Kevin Wolf <kwolf@redhat.com> writes:
> > [...]
> > >> >> >> > diff --git a/monitor/qmp.c b/monitor/qmp.c
> > >> >> >> > index 8469970c69..922fdb5541 100644
> > >> >> >> > --- a/monitor/qmp.c
> > >> >> >> > +++ b/monitor/qmp.c
> > >> >> >> > @@ -135,16 +135,10 @@ static void monitor_qmp_respond(MonitorQMP 
> > >> >> >> > *mon, QDict *rsp)
> > >> >> >> >  
> > >> >> >> >  static void monitor_qmp_dispatch(MonitorQMP *mon, QObject *req)
> > >> >> >> >  {
> > >> >> >> > -    Monitor *old_mon;
> > >> >> >> >      QDict *rsp;
> > >> >> >> >      QDict *error;
> > >> >> >> >  
> > >> >> >> > -    old_mon = monitor_set_cur(&mon->common);
> > >> >> >> > -    assert(old_mon == NULL);
> > >> >> >> > -
> > >> >> >> > -    rsp = qmp_dispatch(mon->commands, req, 
> > >> >> >> > qmp_oob_enabled(mon));
> > >> >> >> > -
> > >> >> >> > -    monitor_set_cur(NULL);
> > >> >> >> > +    rsp = qmp_dispatch(mon->commands, req, 
> > >> >> >> > qmp_oob_enabled(mon), &mon->common);
> > >> >> >> 
> > >> >> >> Long line.  Happy to wrap it in my tree.  A few more in PATCH 
> > >> >> >> 08-11.
> > >> >> >
> > >> >> > It's 79 characters. Should be fine even with your local deviation 
> > >> >> > from
> > >> >> > the coding style to require less than that for comments?
> > >> >> 
> > >> >> Let me rephrase my remark.
> > >> >> 
> > >> >> For me,
> > >> >> 
> > >> >>     rsp = qmp_dispatch(mon->commands, req, qmp_oob_enabled(mon),
> > >> >>                        &mon->common);
> > >> >> 
> > >> >> is significantly easier to read than
> > >> >> 
> > >> >>     rsp = qmp_dispatch(mon->commands, req, qmp_oob_enabled(mon), 
> > >> >> &mon->common);
> > >> >
> > >> > I guess this is highly subjective. I find wrapped lines harder to read.
> > >> > For answering subjective questions like this, we generally use the
> > >> > coding style document.
> > >> >
> > >> > Anyway, I guess following an idiosyncratic coding style that is
> > >> > different from every other subsystem in QEMU is possible (if
> > >> > inconvenient) if I know what it is.
> > >> 
> > >> The applicable coding style document is PEP 8.
> > >
> > > I'll happily apply PEP 8 to Python code, but this is C. I don't think
> > > PEP 8 applies very well to C code. (In fact, PEP 7 exists as a C style
> > > guide, but we're not writing C code for the Python project here...)
> > 
> > I got confused (too much Python code review), my apologies.
> > 
> > >> > My problem is more that I don't know what the exact rules are. Can they
> > >> > only be figured out experimentally by submitting patches and seeing
> > >> > whether you like them or not?
> > >> 
> > >> PEP 8:
> > >> 
> > >>     A style guide is about consistency.  Consistency with this style
> > >>     guide is important.  Consistency within a project is more important.
> > >>     Consistency within one module or function is the most important.
> > >> 
> > >> In other words, you should make a reasonable effort to blend in.
> > >
> > > The project style guide for C is defined in CODING_STYLE.rst. Missing
> > > consistency with it is what I'm complaining about.
> > >
> > > I also agree that consistency within one module or function is most
> > > important, which is why I allow you to reformat my code. But I don't
> > > think it means that local coding style rules shouldn't be documented,
> > > especially if you can't just look at the code and see immediately how
> > > it's supposed to be.
> > >
> > >> >> Would you mind me wrapping this line in my tree?
> > >> >
> > >> > I have no say in this subsystem and I take it that you want all code to
> > >> > look as if you had written it yourself, so do as you wish.
> > >> 
> > >> I'm refusing the bait.
> > >> 
> > >> > But I understand that I'll have to respin anyway, so if you could
> > >> > explain what you're after, I might be able to apply the rules for the
> > >> > next version of the series.
> > >> 
> > >> First, PEP 8 again:
> > >> 
> > >>     Limit all lines to a maximum of 79 characters.
> > >> 
> > >>     For flowing long blocks of text with fewer structural restrictions
> > >>     (docstrings or comments), the line length should be limited to 72
> > >>     characters.
> > >
> > > Ok, that's finally clear limits at least.
> > >
> > > Any other rules from PEP 8 that you want to see applied to C code?
> > 
> > PEP 8 does not apply to C.
> > 
> > > Would you mind documenting this somewhere?
> > >
> > >> Second, an argument we two had on this list, during review of a prior
> > >> version of this patch series, talking about C:
> > >> 
> > >>     Legibility.  Humans tend to have trouble following long lines with
> > >>     their eyes (I sure do).  Typographic manuals suggest to limit
> > >>     columns to roughly 60 characters for exactly that reason[*].
> > >> 
> > >>     Code is special.  It's typically indented, and long identifiers push
> > >>     it further to the right, function arguments in particular.  We
> > >>     compromised at 80 columns.
> > >> 
> > >>     [...]
> > >> 
> > >>     [*] 
> > >> https://en.wikipedia.org/wiki/Column_(typography)#Typographic_style
> > >> 
> > >> The width of the line not counting indentation matters for legibility.
> > >> 
> > >> The line I flagged as long is 75 characters wide not counting
> > >> indentation.  That's needlessly hard to read for me.
> > >> 
> > >> PEP 8's line length limit is a *limit*, not a sacred right to push right
> > >> to the limit.
> > >> 
> > >> Since I get to read this code a lot, I've taken care to avoid illegibly
> > >> wide lines, and I've guided contributors to blend in.
> > >
> > > As I said, I don't mind the exact number much. I do mind predictability,
> > > though. (And ideally also consistency across the project because
> > > otherwise I need to change my editor settings for individual files.)
> > >
> > > So if you don't like 79 columns, give me any other number. But
> > > please, do give me something specific I can work with. "illegibly wide"
> > > is not something I can work with because it's highly subjective.
> > 
> > Taste is subjective.
> > 
> > We can always make CODING_STYLE.rst more detailed.  I view that as a
> > last resort when we waste too much time arguing.
> > 
> > Back to line length.
> > 
> > CODING_STYLE.rst sets a *limit*.
> > 
> > Going over the limit violates CODING_STYLE.rst.  There are (rare) cases
> > where that is justified.
> > 
> > CODING_STYLE.rst neither demands nor prohibits breaking lines before the
> > limit is reached.
> > 
> > Until CODING_STYLE.rst prohibits breaking lines unless they exceed the
> > limit, I will continue to ask for breaking lines when that makes the
> > code easier to read and more consistent with the code around it, for
> > code I maintain, and admittedly in my opinion.
> > 
> > These requests appear to irk you a great deal.  I don't understand, but
> > I'm sorry about it all the same.  By arguing about it repeatedly, you've
> > irked some back.  Brought it on myself, I guess.  However, if that's
> > what it takes to keep the code I maintain legible and consistent, I'll
> > pay the price.
> 
> I conclude that I'll never be able to submit code that passes your
> review in the first attempt because I don't know the specific criteria
> (and you don't seem to know them either before you see the patch).
> 
> Fine, I'll live with it. It's just one of the things that makes working
> in your subsystems more frustrating than in others.

Hmm,
  IMHO the thing here is that there's two different things here:

   a) A CODING_STYLE limit - and personally I use every last character
of that when appropriate
   b) For this particular case, Markus is saying he prefers the wrap
there.

I don't think I see (b) as incompatible as a preference, but lets be
sensible; if it's something you want to change in merge that seems
reasonable, if it's something that you ask to change in a respin that's
kind of reasonable, just don't hold up a big patch series for an
argument over something that's legal in the coding style and isn't
particularly offensive!

Dave

> Kevin
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK