Drop preprocess op of hook_captcha?

solving this will also make #463008: case insensitive Image CAPTCHA only shows lower case characters go away

Committed first part of this issue: making a global option for case insensitive validation:
http://drupal.org/cvs?commit=211820

Case sensitive/insensitive validation is now in
last question: can preprocess be dropped for something better?

Hi Fabiano, It's been a while indeed ;)

Don't worry, I won't drop preprocess op before I am sure of something better.
The problem is that the preprocess op is rather limited in functionality, and working with it feels like overcomplicating things/reinventing the wheel.

Take this use case for example: http://drupal.org/node/440490#comment-1601638
In this case, it would be easier if the validation itself could be done by that module, instead of only letting it preprocess the response before validation, without even knowing the original question or correct solution.

I'll try to come up with an example module that illustrates how this could be done more cleanly. I even think it's possible to do it in a way that is backwards compatible with the CAPTCHA API of 5.x-3.x and 6.x-1.x.
So nobody will be hurt :)

^{edit: small typo}

A small example to illustrate how the preprocess functionality can be achieved with standard Drupal's form API stuff. Hence my "reinventing the wheel" remark.

You can add additional process callbacks with the '#process' property. In the following example I added such a '#process' property to the default Math CAPTCHA from the CAPTCHA module. This callback preprocesses the response by adding one to it, so to get past the CAPTCHA, you have to enter one less than the real solution.

function captcha_captcha($op, $captcha_type = '') {
...
    case 'generate':
...
        $result['form']['captcha_response'] = array(
          '#type' => 'textfield',
          '#title' => t('Math question'),
          '#description' => t('Solve this simple math problem and enter the result. E.g. for 1+3, enter 4.'),
          '#field_prefix' => t('@x + @y = ', array('@x' => $x, '@y' => $y)),
          '#size' => 4,
          '#maxlength' => 2,
          '#required' => TRUE,
          '#process' => array('captcha_math_process'),
...
}

function captcha_math_process($element, $edit, &$form_state, $complete_form) {
  $element['#value'] += 1;
  return $element;
}

in attachment a patch to try it out with the version from HEAD (6.x-2.x-dev).

I think we should drop the preprocess op because it is much cleaner to do the same (and maybe more) with the standard Drupal Form API. It will make the CAPTCHA API smaller, cleaner and simpler, and it promotes the usage of standard Drupal techniques.

Also note that this is backwards compatible with the CAPTCHA API of 5.x-3.x and 6.x-1.x. So CAPTCHA modules that work with this "preprocessless" CAPTCHA 6.x-2.x API will also work with the old 6.x-1.x API.

Here is a first patch to remove the preprocess op from hook_captcha

I just updated the challenges of CAPTCHA Pack to be compatible with a preprocessless CAPTCHA API. No more need for preprocess in CAPTCHA pack ! ;)

The code of those challenges looks now much cleaner and I could remove an ugly hack from the random CAPTCHA type challenge.

I also made a patch for reCAPTCHA to make that module compatible with dropping preprocess: #469594: use #process instead of preprocess (CAPTCHA 6.x-2.x API update)

Yay, Rob committed the patch from #469594: use #process instead of preprocess (CAPTCHA 6.x-2.x API update), so reCAPTCHA module is now also compatible with a preprocessless CAPTCHA API,

Wundo, are you still in doubt about dropping preprocess, and if so, why?

I'd like to push this ASAP, so CAPTCHA for Drupal 6 can finally get past beta.

related issue
#473002: Provide a way to define custom CAPTCHA validation

(reroll)

wundo, are you there?

I can't reach wundo (I also tried IRC and email), but this issue is blocking any further work on the 6.x-2.x branch,
so I decided to commit this:
http://drupal.org/cvs?commit=225020

there is always the 6.x-1.x branch if one needs the preprocess op