How to autoload custom annotation classes without using AnnotationRegistry?

I’m using Doctrine Annotations library (not the whole Doctrine, only annotations) and want to make a custom annotation class.

composer.json:

{
  "require": {
    "doctrine/annotations": "^1.6"
  },
  "autoload": {
    "psr-4": {
      "annotations\": "annotations",
      "entities\": "entities"
    }
  }
}

index.php:

<?php

require 'vendor/autoload.php';

use DoctrineCommonAnnotationsAnnotationReader;

$annotationReader = new AnnotationReader();
$reflectionClass = new ReflectionClass(entitiesMyClass::class);
$classAnnotations = $annotationReader->getClassAnnotations($reflectionClass);
var_dump($classAnnotations);

entities/MyClass.php

<?php

namespace entities;

use annotationsTestAnnotation;

/**
 * @TestAnnotation("123")
 */
class MyClass
{

}

annotations/TestAnnotation.php

<?php

namespace annotations;

/**
 * @Annotation
 * @Target("CLASS")
 */
final class TestAnnotation
{
    /**
     * @var string
     */
    public $value;
}

It gives me the following error:

[Semantical Error] The annotation "@annotationsTestAnnotation" in class entitiesMyClass does not exist, or could not be auto-loaded.

The only solution i found on the Internet is to use AnnotationRegistry::registerLoader or something similar, but it is deprecated so i’d like to solve the problem in another way.

Answer

One way to work around registering a loader is explicit require_once of all files with custom annotations somewhere during application’s bootstrap (such approach was used in the MongoDB ODM but was dropped).

In the next major version annotations will rely on autoloading so no code will be required for the setup. To have a future-proof code you could use:

use DoctrineCommonAnnotationsAnnotationRegistry;

if (class_exists(AnnotationRegistry::class)) {
    AnnotationRegistry::registerLoader('class_exists');
}

You could explicitly pass Composer’s autoloader but class_exists will work just fine given Composer’s autoloader is already in use.