Form hook not found through module_hook_info in module subdirectory

Question

Context: In my Drupal 7 project, I have a module with several submodules. Because the module's root directory got crowded, I moved the submodule files to their own directories within the root.

My module's structure is like this:

mymodule
├── mymodule.info
├── mymodule.module
├── mymodule1
│   ├── mymodule1.block.inc
│   ├── mymodule1.form.inc
│   ├── mymodule1.info
│   ├── mymodule1.module
│   ├── mymodule1.page.inc
│   └── pages
│       └── foo.tpl.php
└── mymodule2
    ├── classes
    │   └── foo
    │       └── Bar.php
    ├── mymodule2.form.inc
    ├── mymodule2.info
    ├── mymodule2.install
    ├── mymodule2.module
    ├── mymodule2.page.inc
    └── pages
        ├── foo.tpl.php
        └── bar.tpl.php

Before "the big move", files that are now in the subdirectories mymodule1 and mymodule2, were located in their parent directory (the module's root directory).

---

The problem: Ever since moving the files, my custom forms are not loading anymore. I have a form in mymodule1.form.inc, which used to load and render perfectly before. Now, when I use drupal_get_form() to load the form, I only get an empty form with a hidden build ID input.

Keep in the mind that the only thing that has changed here, is that the .inc files have been moved to the subdirectory, along with the module file. Also, drupal_get_path('module', 'mymodule1') returns the correct path to the module in the subdirectory.

Strangely, there are also block hooks, located in mymodule1.block.inc, which work perfectly fine, even after clearing all caches.

This is the first time I'm working with separate directories per submodule within a module. I got the inspiration from the module i18n, which uses the same construction. I searched in the Drupal documentation and the code of i18n, but could not find where I'm going wrong.

Does anyone know where I could possibly have gone wrong, or if I need to add data to mymodule1.module or mymodule1.info to make this work? Thank you.

---

Some details: Caches were cleared through <path to project>/admin_menu/flush-cache multiple times.

I use module1_hook_info() to direct the hooks for blocks and forms to separate files. This is the return value:

array (size=9)
  'block_info' => 
    array (size=1)
      'group' => string 'block' (length=5)
  'block_configure' => 
    array (size=1)
      'group' => string 'block' (length=5)
  'block_save' => 
    array (size=1)
      'group' => string 'block' (length=5)
  'block_view' => 
    array (size=1)
      'group' => string 'block' (length=5)
  'forms' => 
    array (size=1)
      'group' => string 'form' (length=4)
  'form' => 
    array (size=1)
      'group' => string 'form' (length=4)
  'form_validate' => 
    array (size=1)
      'group' => string 'form' (length=4)
  'form_submit' => 
    array (size=1)
      'group' => string 'form' (length=4)
  'form_alter' => 
    array (size=1)
      'group' => string 'form' (length=4)

My form functions are called:

• mymodule1_foobar_form
• mymodule1_foobar_form_validate
• mymodule1_foobar_form_submit

Answer 1

Thanks to Clive I found module_load_include(), which is used to load files when working with a form. I moved hook_forms() back to my main module's file and now load the mymodule1.form.inc through there, like so:

/**
 * Implements hook_forms().
 */
function mymodule1_forms($form_id, $args)
{
    module_load_include('inc', 'mymodule1', 'mymodule1.form');
    $forms = array();

    $forms['mymodule1_foo_form'] = array(
        'callback' => 'mymodule1_foo_form',
    );

    return $forms;
}

Now all my forms are loading correctly (again), over both mymodule1 and mymodule2.

The one thing I'm not sure about, that whether this could have been achieved without redundantly declaring the form callbacks to their same-named form IDs.

Answer 2

I'm going to take a stab at what happened here, I might be wrong.

hook_form() isn't a normal hook, it's only invoked for modules that define node types (you haven't indicated any of yours do). It isn't invoked when you arbitrarily invoke drupal_get_form(). Same goes for hook_form_validate() and hook_form_submit().

Some of the hooks in your hook_hook_info() implementation are called for all modules, though. e.g. hook_forms() and hook_form_alter().

I would surmise that mymodule contained an implementation of hook_form_alter() or hook_forms(), which was coincidentally invoked on the same page(s) as the forms that you've now moved to mymodule1 were displayed. Those hooks being invoked implicitly result in mymodule.form.inc being included, and the functions were available.

Now that you've moved the code into mymodule1, I'm guessing you haven't implemented either of the hooks that would have resulted in that coincidental behaviour. So Drupal now can't find your form function, and fails silently.

To fix, include the file manually:

module_include('inc', 'mymodule1', 'mymodule1.form');