Add proxy api endpoint for the composer versions file

src/Controller/ApiController.php

@@ -31,6 +31,7 @@
 use Symfony\Component\HttpFoundation\JsonResponse;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\HttpKernel\EventListener\AbstractSessionListener;
 use Symfony\Component\HttpKernel\Exception\BadRequestHttpException;
 use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 use Symfony\Component\Routing\Attribute\Route;
@@ -49,6 +50,8 @@ enum ApiType
  */
 class ApiController extends Controller
 {
+    private const COMPOSER_VERSIONS_URL = 'https://getcomposer.org/versions';
+
     private const REGEXES = [
         'gitlab' => '{^(?:ssh://git@|https?://|git://|git@)?(?P<host>[a-z0-9.-]+)(?::[0-9]+/|[:/])(?P<path>[\w.-]+(?:/[\w.-]+?)+)(?:\.git|/)?$}i',
         'any' => '{^(?:ssh://git@|https?://|git://|git@)?(?P<host>[a-z0-9.-]+)(?::[0-9]+/|[:/])(?P<path>[\w.-]+(?:/[\w.-]+?)*)(?:\.git|/)?$}i',
@@ -82,6 +85,34 @@ public function packagesAction(string $webDir): Response
         return new Response('Horrible misconfiguration or the dumper script messed up, you need to use bin/console packagist:dump-v2', 404);
     }
 
+    /**
+     * Proxies https://getcomposer.org/versions so that systems which can only reach
+     * packagist.org are still able to read Composer's version metadata.
+     *
+     * The response is cached at the CDN edge via s-maxage as this data changes rarely.
+     */
+    #[Route(path: '/api/composer-versions', name: 'composer_versions', defaults: ['_format' => 'json'], methods: ['GET'])]
+    public function composerVersionsAction(): Response
+    {
+        try {
+            $upstream = $this->httpClient->request('GET', self::COMPOSER_VERSIONS_URL);
+            if ($upstream->getStatusCode() !== 200) {
+                throw new \RuntimeException('Unexpected status code '.$upstream->getStatusCode());
+            }
+            $contents = $upstream->getContent();
+        } catch (\Throwable $e) {
+            $this->logger->error('Failed to proxy '.self::COMPOSER_VERSIONS_URL, ['exception' => $e]);
+
+            return new JsonResponse(['status' => 'error', 'message' => 'Failed to fetch upstream version data, please try again later.'], 502);
+        }
+
+        $response = new Response($contents, 200, ['Content-Type' => 'application/json']);
+        $response->setSharedMaxAge(900);
+        $response->headers->set(AbstractSessionListener::NO_AUTO_CACHE_CONTROL_HEADER, 'true');
+
+        return $response;
+    }
+
     #[Route(path: '/api/create-package', name: 'generic_create', defaults: ['_format' => 'json'], methods: ['POST'])]
     public function createPackageAction(Request $request, ProviderManager $providerManager, GitHubUserMigrationWorker $githubUserMigrationWorker, RouterInterface $router, ValidatorInterface $validator): JsonResponse
     {

tests/Controller/ApiControllerTest.php

@@ -19,6 +19,8 @@
 use App\Tests\IntegrationTestCase;
 use PHPUnit\Framework\Attributes\DataProvider;
 use PHPUnit\Framework\Attributes\Depends;
+use Symfony\Component\HttpClient\MockHttpClient;
+use Symfony\Component\HttpClient\Response\MockResponse;
 
 class ApiControllerTest extends IntegrationTestCase
 {
@@ -282,4 +284,36 @@ public function testBearerTokenAuthenticationOverridesQuery(): void
 
         $this->assertEquals(202, $this->client->getResponse()->getStatusCode(), $this->client->getResponse()->getContent());
     }
+
+    public function testComposerVersionsProxiesUpstream(): void
+    {
+        $body = '{"stable":[{"path":"/download/2.7.1/composer.phar","version":"2.7.1"}]}';
+        $mockClient = new MockHttpClient(function (string $method, string $url) use ($body) {
+            $this->assertSame('GET', $method);
+            $this->assertSame('https://getcomposer.org/versions', $url);
+
+            return new MockResponse($body, ['http_code' => 200, 'response_headers' => ['Content-Type' => 'application/json']]);
+        });
+        self::getContainer()->set('http_client', $mockClient);
+
+        $this->client->request('GET', '/api/composer-versions');
+        $response = $this->client->getResponse();
+
+        $this->assertSame(200, $response->getStatusCode(), (string) $response->getContent());
+        $this->assertSame($body, $response->getContent());
+        $this->assertStringContainsString('application/json', (string) $response->headers->get('Content-Type'));
+        $this->assertStringContainsString('s-maxage=900', (string) $response->headers->get('Cache-Control'));
+    }
+
+    public function testComposerVersionsReturns502OnUpstreamFailure(): void
+    {
+        $mockClient = new MockHttpClient(new MockResponse('nope', ['http_code' => 500]));
+        self::getContainer()->set('http_client', $mockClient);
+
+        $this->client->request('GET', '/api/composer-versions');
+        $response = $this->client->getResponse();
+
+        $this->assertSame(502, $response->getStatusCode());
+        $this->assertJsonStringEqualsJsonString('{"status":"error","message":"Failed to fetch upstream version data, please try again later."}', (string) $response->getContent());
+    }
 }