[phobos] enforce() improvement

[Andrei Alexandrescu]

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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