[phobos] enforce() improvement
Lars Tandle Kyllingstad
lars at kyllingen.net
Thu Jul 1 11:22:15 PDT 2010
Oh, I see. Well, ignore my last message then -- I sent it before I read
this one. :)
-Lars
On Thu, 2010-07-01 at 11:19 -0700, Steve Schveighoffer wrote:
> I re-read this thread. I understand now that you don't want to remove that information, just not print it via msg? Sorry for the opposition. I agree that the message shouldn't contain redundant info.
>
> As long as the default handler prints the information out, I'm ok with that. Having as much information as possible when something goes unexpectedly wrong is the best case scenario for a developer.
>
> -Steve
>
>
>
> ----- Original Message ----
> > From: Lars Tandle Kyllingstad <lars at kyllingen.net>
> > To: Discuss the phobos library for D <phobos at puremagic.com>
> > Sent: Thu, July 1, 2010 2:06:45 PM
> > Subject: Re: [phobos] enforce() improvement
> >
> > There is no need to add anything, Throwable already has this structure.
> That
> > was the main point behind my proposal: enforce() puts the
> information
> > in the wrong place.
>
> I'll look into it.
>
> -Lars
>
>
>
> On
> > Thu, 2010-07-01 at 10:47 -0700, Andrei Alexandrescu wrote:
> > I think it
> > would be a good improvement to add such structure to
> > exceptions. So
> > toString() would continue to print essentially the same
> > message, but it
> > would assemble it from the separately-available
> > properties file, line,
> > and reason.
> >
> > Go for it, or submit a ticket so it's not
> > forgotten.
> >
> > Andrei
> >
> > Lars Tandle Kyllingstad
> > wrote:
> > > The library user would still get the information,
> > because
> > > Throwable.toString() would still give the file and line
> > number, and like
> > > I said, Throwable.file and Throwable.line are
> > supposed to be filled with
> > > that information. My point was
> > that enforce() puts the information in
> > > Throwable.msg, which I find
> > completely redundant.
> > >
> > > Also, if you are using plain
> > enforce() for error checking (like Phobos
> > > does in a lot of places),
> > Throwable.msg is your only source of
> > > information to pass to the
> > user, since enforce() by default throws an
> > > Exception and not an
> > InsightfulInformationException.
> > >
> > > -Lars
> > >
> >
> > >
> > >
> > > On Thu, 2010-07-01 at 07:00 -0700,
> > Steve Schveighoffer wrote:
> > >> I disagree. The "user" in this
> > case, is the user of the library code. He does in fact need to know the
> > file/line that caused the problem, and more useful would be the full stack trace
> > so he can see where his code used the offending value.
> > >>
> >
> > >> If you are relying on enforce to give insightful error messages to an
> > actual user (that is, someone who runs your program), then you need some
> > training in user interface design :)
> > >>
> > >>
> > -Steve
> > >>
> > >>
> > >>
> > >> -----
> > Original Message ----
> > >>> From: Lars Tandle Kyllingstad <
> > ymailto="mailto:lars at kyllingen.net"
> > href="mailto:lars at kyllingen.net">lars at kyllingen.net>
> > >>>
> > To: Phobos mailing list <
> > href="mailto:phobos at puremagic.com">phobos at puremagic.com>
> >
> > >>> Sent: Thu, July 1, 2010 9:50:15 AM
> > >>> Subject:
> > [phobos] enforce() improvement
> > >>>
> > >>> Often,
> > at least in small programs, when an exception is thrown you just
> >
> > >> want
> > >>> to present a sensible message to the user
> > and abort the
> > >>> current
> > >> operation.
> > Example:
> > >>
> > >> void
> >
> > >>> doStuff(int i) { enforce(i >= 0, "Need nonnegative i");
> > }
> > >>
> > >>> try
> > doStuff(-1);
> > >> catch
> >
> > >>> (Exception e) writeln("Error: ", e.msg);
> > >> In this
> > case, the user will
> > >>> see
> > >>
> > Error: b.d(5): Need nonnegative
> > >>> i
> >
> > >> My point is that the user doesn't need to see the file and line
> >
> > >>> number
> > >> that caused the error. This
> > is only useful for the
> > >>> programmer. So I
> >
> > >> suggest we make either of the following changes to
> >
> > >>> enforce():
> > >> 1. Drop the file
> > and line number from the
> > >>> message. The
> > Throwable
> > >> class has dedicated
> >
> > >>> 'file' and 'line' fields which we can
> >
> > >> populate
> > >>> with that
> > information without polluting the error
> > >>
> >
> > >>> message.
> > >> 2.
> > Another option is to include the file and line
> > >>> only in
> > debug
> > >> builds.
> >
> > >>
> > >> -Lars
> > >>
> > >>
> > _______________________________________________
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> >
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> > >>
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> > >>
> >
> > >>
> > >>
> > >>
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