Issue #2848927 by Wim Leers, alexpott: EntityResource::addLinkHeaders() should...

Issue #2848927 by Wim Leers, alexpott: EntityResource::addLinkHeaders() should use LinkRelationType plugin instances rather than definitions

core/modules/rest/src/Plugin/rest/resource/EntityResource.php

@@ -432,7 +432,10 @@ public function calculateDependencies() {
    */
   protected function addLinkHeaders(EntityInterface $entity, Response $response) {
     foreach ($entity->getEntityType()->getLinkTemplates() as $relation_name => $link_template) {
-      if ($definition = $this->linkRelationTypeManager->getDefinition($relation_name, FALSE)) {
+      if ($this->linkRelationTypeManager->hasDefinition($relation_name)) {
+        /** @var \Drupal\Core\Http\LinkRelationTypeInterface $link_relation_type */
+        $link_relation_type = $this->linkRelationTypeManager->createInstance($relation_name);
+
         $generator_url = $entity->toUrl($relation_name)
           ->setAbsolute(TRUE)
           ->toString(TRUE);
@@ -440,10 +443,10 @@ protected function addLinkHeaders(EntityInterface $entity, Response $response) {
           $response->addCacheableDependency($generator_url);
         }
         $uri = $generator_url->getGeneratedUrl();
-        $relationship = $relation_name;
-        if (!empty($definition['uri'])) {
-          $relationship = $definition['uri'];
-        }
+
+        $relationship = $link_relation_type->isRegistered()
+          ? $link_relation_type->getRegisteredName()
+          : $link_relation_type->getExtensionUri();
 
         $link_header = '<' . $uri . '>; rel="' . $relationship . '"';
         $response->headers->set('Link', $link_header, FALSE);

core/modules/rest/tests/src/Functional/EntityResource/EntityResourceTestBase.php

@@ -424,11 +424,11 @@ public function testGet() {
     if ($this->entity->getEntityType()->getLinkTemplates()) {
       $this->assertArrayHasKey('Link', $response->getHeaders());
       $link_relation_type_manager = $this->container->get('plugin.manager.link_relation_type');
-      $expected_link_relation_headers = array_map(function ($rel) use ($link_relation_type_manager) {
-        $definition = $link_relation_type_manager->getDefinition($rel, FALSE);
-        return (!empty($definition['uri']))
-          ? $definition['uri']
-          : $rel;
+      $expected_link_relation_headers = array_map(function ($relation_name) use ($link_relation_type_manager) {
+        $link_relation_type = $link_relation_type_manager->createInstance($relation_name);
+        return $link_relation_type->isRegistered()
+          ? $link_relation_type->getRegisteredName()
+          : $link_relation_type->getExtensionUri();
       }, array_keys($this->entity->getEntityType()->getLinkTemplates()));
       $parse_rel_from_link_header = function ($value) use ($link_relation_type_manager) {
         $matches = [];