Hi sebb,

>Another aspect of debugging is ensuring that methods are small and

>easily tested independently.
>However this is difficult to do, and care must be taken to ensure that
>the public API is not unnecessarily extended..

A very good point.

The parsers in commons-imaging expose some #dump... methods 
(https://github.com/apache/commons-imaging/blob/7e7f96857df999175bb614732e13272a82f7962a/src/main/java/org/apache/commons/imaging/ImageParser.java#L794).

While I can see that parsers may need to dump the data they are holding in some 
structured way for inspecting, reporting, serializing, etc, it looks like some 
other classes were affected by it too. For example...


A JPEG Segment has a #dump() method 


https://github.com/apache/commons-imaging/blob/7e7f96857df999175bb614732e13272a82f7962a/src/main/java/org/apache/commons/imaging/formats/jpeg/segments/Segment.java#L34


which gets defined in each subclass of Segment. It can be confusing to have a 
method such as #dump() in a Segment, from the point of view of someone writing 
a photo editor for example. The user could use that to pass his/her own 
logger's PrintWriter, which would make removing or changing logging in the 
future in commons-imaging.


If we keep the Debug class, and make it internal, there would still be these 
methods to take care. And there are some methods where users can provide a 
PrintWriter, while others instead use System.out 
(e.g.https://github.com/apache/commons-imaging/blob/7e7f96857df999175bb614732e13272a82f7962a/src/main/java/org/apache/commons/imaging/FormatCompliance.java#L70).

Cheers
Bruno

________________________________
From: sebb <seb...@gmail.com>
To: Commons Developers List <dev@commons.apache.org>; Bruno P. Kinoshita 
<brunodepau...@yahoo.com.br> 
Sent: Tuesday, 6 February 2018 11:06 PM
Subject: Re: [imaging] IMAGING-154 remove Debug class



On 6 February 2018 at 09:52, Bruno P. Kinoshita
<brunodepau...@yahoo.com.br.invalid> wrote:
> Hi Jorg,
>
> I'd be fine with that solution too. I think this one would cause the smaller 
> change to the code as is.
>
> I believe my preference is still to remove the Debug class. But between 
> logging and making Debug internal only, I'd choose making it internal.

+1

I think making it internal means it can still be dropped later.

> Looking forward to hearing what others think about these options.
>

Another aspect of debugging is ensuring that methods are small and
easily tested independently.
However this is difficult to do, and care must be taken to ensure that
the public API is not unnecessarily extended..

> Thanks
> Bruno
>
>
> ________________________________
> From: Jörg Schaible <joerg.schai...@bpm-inspire.com>
> To: dev@commons.apache.org
> Sent: Tuesday, 6 February 2018 9:24 PM
> Subject: Re: [imaging] IMAGING-154 remove Debug class
>
>
>
> Hi Bruno,
>
>
> if it might also be helpful to our users, why not keep and provide it. As
>
> I understand it, the Debug class is a tool helping in development to
>
> analyze some behavior.
>
>
> Nothing stops us from declaring this class internal (we might even put it
>
> into a package "internal" or "debug") that might be changed without
>
> further comment. Nobody may rely on it in production code, but during
>
> development it might be helpful. With such an approach we might not have
>
> a need to find a better interface to provide this functionality.
>
>
> Just my 2¢,
>
> Jörg
>
>
>
> Am Mon, 05 Feb 2018 12:20:58 +0000 schrieb Bruno P. Kinoshita:
>
>
>> Hello,
>
>>
>
>> If memory serves me well, some time ago we had a discussion around
>
>> sanselan & commons-imaging 1.0. One of the issues with commons-imaging
>
>> 1.0 was the Debug class.
>
>>
>
>> https://issues.apache.org/jira/browse/IMAGING-154
>
>>
>
>> I finished the pull request, but Gilles raised an important point, about
>
>> discussing other alternatives first.
>
>>
>
>> Initially I am against logging in low level libraries, especially
>
>> commons components. But some time ago I had to debug TIFF issues in
>
>> commons-imaging, and having the dump methods was a tremendous help.
>
>>
>
>>
>
>> The issue is that some imaging algorithms/processing have a lot of
>
>> variables that can be altered. And keeping an eye on all of them in the
>
>> debugger can be quite hard - though not impossible.
>
>>
>
>> So all in all, now I am more confident to proceed without the Debug
>
>> class. But some users could have a hard time investigating possible
>
>> issues in the library without seeing what's going on within the library.
>
>>
>
>> IMO, that could be solved with the logging/dump features... or through a
>
>> better design, especially around exception handling/throwing. The latter
>
>> is my preferred approach. Instead of logging, I prefer - whenever
>
>> possible - that low level libraries throw exceptions and let me handle
>
>> the logging.
>
>>
>
>>
>
>> So, any thoughts? :) I'm +1 to remove the Debug class, and +0 to a
>
>> logging added to commons-imaging.
>
>>
>
>> Bruno
>
>
>
>
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