Use hook_hook_info() to implement hook_form_FORM_ID_alter()s in a separate file

Question

I have a lot of mymodule_form_FORM_ID_alter()s in my module and I want to move them to a separate file (mymodule.form.inc), I found hook_hook_info() but I couldn't figure out how to use it for that specific case.

I tried adding:

$hooks['form_alter'] = array(
  'group' => 'form'
);

to mymodule_hook_info() but it didn't run the form alterers that I moved to the separate file. Any ideas how to get it to work?

Answer 1

It works pretty well, the only thing is that if you want to implement hook_form_FORM_ID_alter(), you need to add:

  $hooks['form_FORM_ID_alter'] = array(
    'group' => 'form'
  );
  return $hooks;

Answer 2

Don't. This is not supported by Drupal core. In fact, hook_hook_info is intended for modules declaring hooks, not modules implementing them.

In addition, if two modules on a site declare a group for the same hook, all uses of the hook in $module.$group.inc files will break.

Instead, create stubs that do a module_load_include, and then a function call.

Answer 3

You can also use the solution found here.

Here's an easy way to get ALL hook_form_FORM_ID_alter() implementations loaded from a .inc file, WITHOUT declaring them each separately in hook_hook_info().

In MY_MODULE.module add the following code.

/**
 * Implements hook_hook_info_alter().
 */
function MY_MODULE_hook_info_alter(&$hooks) {
  $hooks['form_alter']['group'] = 'form'; 
}

Then in MY_MODULE.form.inc make sure to add the following code.

/**
 * Implements hook_form_alter().
 */
function MY_MODULE_form_alter(&$form, &$form_state, $form_id) {
}

// Add all MY_MODULE_form_FORM_ID_alter() functions below here.

With the above MY_MODULE_form_alter() declared in this .inc file (even if it's empty), all MY_MODULE_form_FORM_ID_alter() implementations declared in the same file will get loaded properly. Without this function the file will not be loaded at all.

This works because drupal_prepare_form() calls hook_form_alter() (and loads this .inc file) before calling hook_form_FORM_ID_alter() for each form build.