How can I get a custom module's file path in a preprocess function?

Question

I've got default images located in a custom module directory and I'd like to load them using hook_preprocess_node(). I then will pass the images to the template file.

In the screenshot, I'm loading an image into $default_image, which renders correctly when passed to the template file.

Instead of loading the image from an entity field, I want to read the image directly from the directory in the custom module. Clearly, the path I manually built into $premier_tech_image is incorrect.

The problem is NOT how to access the file. For example, we use code like this for JSON feeds.

$module_handler = $this->moduleHandler;
$module_path = $module_handler->getModule('my_custom_module')->getPath();
$resource = $module_path . '/resources/countries.json';

How do I correctly pass the reference to an image located in the directory of a custom module to the template file?

Answer 1

A Drupal URI starts with a stream wrapper like "public://" that indicates to Drupal how to handle that resource. Typically, the "public" stream wrapper is defined as "treat this resource as a local file within sites/default/files."

Your module assets are not located within sites/default/files, so they cannot use the "public" stream wrapper.

Drupal doesn't actually come out-of-the-box with a registered stream wrapper for module or theme assets. You might try installing https://www.drupal.org/project/system_stream_wrapper, which would then allow you to make a URI like module://tableau_partners_sync/images/premier-technology.png.

Answer 2

Try letting Drupal generate the module path:

$modulePath = \Drupal::service('module_handler')->getModule('MYMODULE')->getPath();
$imagePath = $modulePath . "/images/my-image.jpg";

Answer 3

Drupal 8 still has drupal_get_path(), which is used from Drupal core modules and third-party modules for the path of files contained in modules directories. (See the code for ckeditor_ckeditor_css_alter() or the example code given in hook_js_alter().

function hook_js_alter(&$javascript, \Drupal\Core\Asset\AttachedAssetsInterface $assets) {
  $javascript['core/assets/vendor/jquery/jquery.min.js']['data'] = drupal_get_path('module', 'jquery_update') . '/jquery.js';
}

Deprecate drupal_get_path() and drupal_get_filename() and replace with ExtensionList::getPath() and ExtensionList::getPathname() aims to deprecate the function.
At the moment I am writing this answer, its status is still Needs work (for Drupal 9.3.x). When it's marked as fixed, instead of drupal_get_path('module', $module_name), modules will use \Drupal::service('extension.list.module')->getPath($module_name).

For example, the previous example hook could be rewritten in this way.

function hook_js_alter(&$javascript, \Drupal\Core\Asset\AttachedAssetsInterface $assets) {
  $javascript['core/assets/vendor/jquery/jquery.min.js']['data'] = \Drupal::service('extension.list.module')->getPath('jquery_update') . '/jquery.js';
}

Alternatively, \Drupal::service('extension.path.resolver')->getPath('module', $module_name) could be used, which is what drupal_get_path() and drupal_get_filename() have been deprecated in favor of extension listing services suggests to use in the case the extension type is dynamically specified.