enforce() improvement (page 2)

Yes, perfect. It's a net improvement. Thanks Lars!

Andrei

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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