Merge branch '7.4' into 8.0

* 7.4:
  [Translation] Make the extractor alias optional
  [Cache] Fix accepting named closures as early-expiration callbacks
  [Mime] Update mime types
  [HttpKernel] Conflict with symfony/flex < 2.10
  [Yaml] Align unquoted multiline scalar parsing with spec for comments
  work around limitation in JsonResponse when the data is null
  do not use recipient phone numbers as sender e-mail addresses
  [Dotenv] DotenvDumpCommand cannot be internal

Author: nicolas-grekas

Controller/AbstractController.php

@@ -155,6 +155,10 @@ protected function json(mixed $data, int $status = 200, array $headers = [], arr
             return new JsonResponse($json, $status, $headers, true);
         }
 
+        if (null === $data) {
+            return new JsonResponse('null', $status, $headers, true);
+        }
+
         return new JsonResponse($data, $status, $headers);
     }
 

Tests/Controller/AbstractControllerTest.php

@@ -229,6 +229,37 @@ public function testJsonWithSerializerContextOverride()
         $this->assertEquals('{}', $response->getContent());
     }
 
+    public function testJsonNull()
+    {
+        $controller = $this->createController();
+        $controller->setContainer(new Container());
+
+        $response = $controller->json(null);
+        $this->assertInstanceOf(JsonResponse::class, $response);
+        $this->assertSame('null', $response->getContent());
+    }
+
+    public function testJsonNullWithSerializer()
+    {
+        $container = new Container();
+
+        $serializer = $this->createMock(SerializerInterface::class);
+        $serializer
+            ->expects($this->once())
+            ->method('serialize')
+            ->with(null, 'json', ['json_encode_options' => JsonResponse::DEFAULT_ENCODING_OPTIONS])
+            ->willReturn('null');
+
+        $container->set('serializer', $serializer);
+
+        $controller = $this->createController();
+        $controller->setContainer($container);
+
+        $response = $controller->json(null);
+        $this->assertInstanceOf(JsonResponse::class, $response);
+        $this->assertSame('null', $response->getContent());
+    }
+
     public function testFile()
     {
         $container = new Container();