Nothing is forever

I have been writing about the scaffolding metaphor - but after some conversations with my colleagues I realized that I did not do a good job there. I did not conduct well the main idea: nothing is forever. No library and no program is forever and we should not shy off from writing libraries that are useful only at some phase of the application construction. It is still valuable if you can quickly get to the point of having a preview, a simplified prototype of the functionality you need even if eventually you'll remove all of that prototype code from the project. This is very 'agile' and it is also 'worse is better (if you can have it early)' and those libraries, those tools that you use only temporarily, I call the scaffolding.

Now one would ask why write a library that is useful only temporarily? Why not include at once all the parts needed in the final product? There can be several reasons:

• something that is only a part of the scaffolding in one project can stay in the final solution in another one
  
• the author of the library might not yet fully understand the problem, and it can take years to reach the right abstraction
  
• the distribution of possibly needed modification can be so uniform that there is no reason to concentrate on one of them more than on another one and it is virtually impossible to cover them all
  
• and finally: nothing is forever - you never know where a project will go in the future and what you'll need to change
  

A good example (of the third point) are code samples from manuals - you copy them to quickly get something working - but later you modify it and sometimes you change every character from the original. Another one can be the scaffolding code in Rails - you can debate if it fits the first or the second or other points - but it was useful to a lot of people.

Every library can be used as scaffolding - so why not accept this and help the developers in using it that way?

CPAN and code reuse

CPAN is wonderful thing - it is a great achievement of the whole Perl community and the thing that makes it apart from other languages. But somehow it works mostly for libraries. And what about the other modes of code reuse? How about CPAN for code examples? One can say we don't need CPAN for code examples - everyone is using code examples all the time and they do that without any special infrastructure. But what I see around is that some of CPAN modules are actually code examples in disguise. Some of them would be better without any code in the package and only documentation and tests validating the documented techniques. Hmm maybe we don't really need a separate CPAN for that - maybe we can keep them at the existing one - and just mark them in a special way? And maybe we need some social acceptance for packaging such 'empty' libraries?

And what with applications?

Code reuse styles

There is much buzz around PHP tools like Drupal and Joomla. They are ready-made solutions, but in fact there is also a lot of tweaking the templates and writing add-ons. It seems to work very well - the clients get something usable from the beginning - and later they can modify it to fit their purpose better. This is very agile. In contrast the reuse in Perl is mostly around libraries. This is much more flexible - you don't tweak a ready solution - you assemble it from the thousands of CPAN packages. But it is also less agile.

I wonder why it is like that. There are some technical differences that lead developers in one or the other direction - but there is also a cultural/psychological cause. Doing some self-analysis I must admit that I am not really enthusiastic about contributing to a Perl CMS (like for example Bricolage) - in my view all the already-build solutions use obsolete libraries. I'd rather contribute to building the perfect library - then code an extension to Bricloage. I have the feeling that I am not alone in that crazy perfectionism around Perl hackers. PHP clearly wins here with more pragmatic approach.

Deprecated code analyzer for HTML::FormHandler

So the other day I've read Deprecated code analyzer for perl and I thought - this is a GREAT idea! And I stole it for HTML::FormHandler. Now with new releases our users will have a tool to find all the deprecated API calls in their code.

Is using the Catalyst 'forward' method a cargo cult?

I think most Catalyst new-commers believe that to execute a Catalyst action you need to forward to it - this is the effect of all the examples in the manual doing that instead of using the standard Perl syntax of calling a method on a class. Of course there are some differences between those two - but I am sure that for most cases the standard Perl way of doing it is perfectly enough.

And when it is not enough? What are really the differences between:

$c->forward( 'some_action' )

and the standard Perl:

$self->some_action( $c );

As far as I know the only two differences are that the first call is called in an eval and that it is logged in the debug output (if it is switched on), maybe there are some other minor differences, but, I am sure, nothing dramatical. It can helpful/needed sometimes (and othertimes that eval can be a nuisance), but it is also easy to add. Of course this is the simplest case - 'forward' signature is more complex and it does amazing things for finding the action "by it's private name" - but for most of the cases you ain't gonna need it and you can use ye old Perl syntax to make the call and spare yourself learning how to pass parameters to the forward call.

Related reading: Premature Flexibilization Is The Root of Whatever Evil Is Left - a reddit discussion.

Functional versus Unit testing

Benefits of automated functional testing (was: Why unit testing is a waste of time) is a comprehensive list of arguments for functional and against unit testing. It is a bit long and maybe it is preaching to the choir as I have never seen unit testing in CPAN modules, but it might be handy if you needed to convince your co-workers.

Also discussed at Hacker News

InstantCRUD and FormHandler

The new version of Catalyst::Example::InstantCRUD is on CPAN. This version uses FormHandler, is a bit nicer visually (I hope) and has a proof of concept experimental REST interface.