docs: add guide for custom TagCollector service (#6348)

Co-authored-by: Antoine Bluchet <soyuka@users.noreply.github.com>

docs/config/packages/framework.yaml

@@ -8,6 +8,10 @@ api_platform:
   docs_formats:
     jsonopenapi: ['application/vnd.openapi+json']
   keep_legacy_inflector: false
+  http_cache:
+        invalidation:
+            enabled: true
+        public: true
   use_symfony_listeners: false
   defaults:
     extra_properties:

docs/guides/http-cache-tags.php

@@ -0,0 +1,121 @@
+<?php
+// ---
+// slug: http-cache-tags
+// name: Customize HTTP Cache Tags
+// executable: true
+// position: 21
+// ---
+
+// This guide describes how to customize HTTP Cache Tags included in the API response header by registering a TagCollector service. In this example, the Id 
+// of a resource will be used to generate the cache tag instead of its IRI.
+// 
+// If you only want to add additional tags without changing them, it might be sufficient to follow the [standard documentation on http cache](https://api-platform.com/docs/core/performance/#extending-cache-tags-for-invalidation).
+//
+// First, we need our book resource. For the sake of this example, we assume the id to be unique across all resources (otherwise replacing the IRI with Id would make no sense).
+namespace App\ApiResource {
+    use ApiPlatform\Metadata\ApiResource;
+    use ApiPlatform\Metadata\ApiProperty;
+    use ApiPlatform\Metadata\Get;
+    use ApiPlatform\Metadata\Operation;
+
+    #[ApiResource(
+        operations: [
+            new Get(provider: Book::class.'::provide'),
+        ],
+    )]
+    class Book
+    {
+        #[ApiProperty(identifier: true)]
+        public string $id = "unique-id-1";
+
+        public static function provide(Operation $operation, array $uriVariables = [], array $context = []): object|array|null
+        {
+            return (new self());
+        }
+    }
+}
+
+// Now, we define our TagCollector service. Check the PHPDoc in TagCollectorInterface to see the various information, which is available within `$context`.
+//
+// Add any tags you want to be included in the response to `$context['resources']`.
+
+namespace App\Service {
+    use ApiPlatform\Serializer\TagCollectorInterface;
+    use App\ApiResource\Book;
+
+    class TagCollector implements TagCollectorInterface
+    {
+        public function collect(array $context = []): void 
+        {
+            if (isset($context['property_metadata'])) {
+                return;
+            }
+
+            $iri = $context['iri'] ?? null;
+            $object = $context['object'] ?? null;
+
+            if ($object && $object instanceof Book) {
+                $iri = $object->id;
+            }
+
+            if (!$iri) {
+                return;
+            }
+
+            $context['resources'][$iri] = $iri;
+        }
+    }
+}
+
+// Replace the service 'api_platform.http_cache.tag_collector' with your new TagCollector class.
+
+namespace App\DependencyInjection {
+    use App\Service\TagCollector;
+    use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;
+
+    function configure(ContainerConfigurator $configurator): void
+    {
+        $services = $configurator->services();
+        $services->set('api_platform.http_cache.tag_collector', TagCollector::class);
+    }
+}
+
+
+// Request the book. When using Swagger UI, you should see that your 'Cache-Tags' header now includes the Id only instead of the full Iri.
+
+namespace App\Playground {
+    use Symfony\Component\HttpFoundation\Request;
+
+    function request(): Request
+    {
+        return Request::create('/books/unique-id-1.jsonld', 'GET');
+    }
+}
+
+// ...or verify directly in testing.
+
+namespace App\Tests {
+    use ApiPlatform\Playground\Test\TestGuideTrait;
+    use ApiPlatform\Symfony\Bundle\Test\ApiTestCase;
+
+    final class BookTest extends ApiTestCase
+    {
+        use TestGuideTrait;
+
+        public function testAsAnonymousICanAccessTheDocumentation(): void
+        {
+            $response = static::createClient()->request('GET', '/books/unique-id-1.jsonld');
+
+            $this->assertResponseIsSuccessful();
+            $this->assertResponseHeaderSame('Cache-Tags', 'unique-id-1');
+            $this->assertJsonContains([
+                '@id' => '/books/unique-id-1',
+                '@type' => 'Book',
+                'id' => 'unique-id-1',
+            ]);
+        }
+    }
+}
+
+
+// If you rely on invalidation from Api-Platform, don't forget that you'd also need to have your own implementation of `PurgeHttpCacheListener`. Otherwise the wrong tags will be purged.