I tried following this guide: https://www.drupal.org/docs/8/api/restful-web-services-api/custom-rest-resources for the REST API.

However, when enabling the module, I get:

Fatal error: Cannot declare class Drupal\my_module_rest_api\Plugin\rest\resource\MyModuleResource, because the name is already in use in [PATH]\modules\my_module\src\Plugin\rest\resource\MyModuleResource.php on line 0

It seems like it could be a simple class naming error, but I really tried following the guide to a tee. Here is MyModuleResource.php in full:


namespace Drupal\my_module_rest_api\Plugin\rest\resource;

use Drupal\rest\Plugin\ResourceBase;
use Drupal\rest\ResourceResponse;

 * Provides a REST API Resource
 * @RestResource(
 *   id = "my_module_resource",
 *   label = @Translation("My Module Resource"),
 *   uri_paths = {
 *     "canonical" = "/my_module_rest_api/my_module_resource"
 *   }
 * )
class MyModuleResource extends ResourceBase {

     * Responds to entity GET requests.
     * @return \Drupal\rest\ResourceResponse
    public function get() {
        $response = ['message' => 'Hello, this is a rest service'];
        return new ResourceResponse($response);

Here is the rest.resource.my_module_resource.yml file:

id: my_module_resource
plugin_id: my_module_resource
granularity: method
      - json
      - basic_auth
  • 1
    The error suggests you have two copies of the same file, in different modules. If not, run composer dump-autoload; drush cr and try again
    – Clive
    Commented May 21, 2018 at 13:48
  • Unfortunately it didn't work (no change). I have added the REST resource YML content if it helps.
    – Ynhockey
    Commented May 22, 2018 at 9:11

1 Answer 1


It looks like the problem was not with the REST API routes, but with the module name vs. namespace: in trying to pay attention to the details of the REST API extension, I missed that my module name was different from the namespace. In the above example, the module name is


while the namespace is


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