Extract annotation reader setup to a provider class

[MAILPOET-2437]

lib/Doctrine/Annotations/AnnotationReaderProvider.php

@@ -0,0 +1,30 @@
+<?php
+
+namespace MailPoet\Doctrine\Annotations;
+
+use MailPoetVendor\Doctrine\Common\Annotations\AnnotationReader;
+use MailPoetVendor\Doctrine\Common\Annotations\AnnotationRegistry;
+use MailPoetVendor\Doctrine\Common\Annotations\CachedReader;
+use MailPoetVendor\Doctrine\Common\Cache\ArrayCache;
+
+class AnnotationReaderProvider {
+  /** @var CachedReader */
+  private $annotation_reader;
+
+  function __construct() {
+    // register annotation reader if doctrine/annotations package is installed
+    // (i.e. in dev environment, on production metadata is dumped in the build)
+    $read_annotations = class_exists(CachedReader::class) && class_exists(AnnotationReader::class);
+    if ($read_annotations) {
+      // autoload all annotation classes using registered loaders (Composer)
+      // (needed for Symfony\Validator constraint annotations to be loaded)
+      AnnotationRegistry::registerLoader('class_exists');
+      $this->annotation_reader = new CachedReader(new AnnotationReader(), new ArrayCache());
+    }
+  }
+
+  /** @return CachedReader|null */
+  function getAnnotationReader() {
+    return $this->annotation_reader;
+  }
+}