Fixed bug that the type of rpc result does not support types which allows null. (#3434)

* Fixed bug that the type of rpc result does not support types which allows null.

* Added test cases

CHANGELOG-2.1.md

@@ -1,5 +1,9 @@
 # v2.1.12 - TBD
 
+## Fixed
+
+- [3434](https://github.com/hyperf/hyperf/pull/3434) Fixed bug that the type of rpc result does not support types which allows null.
+
 # v2.1.12 - 2021-03-29
 
 ## Fixed

src/json-rpc/tests/RpcServiceClientTest.php

@@ -162,6 +162,29 @@ class RpcServiceClientTest extends TestCase
         $this->assertEquals($uniqid, $ret);
     }
 
+    public function testProxyReturnNullableTypeWithNull()
+    {
+        $container = $this->createContainer();
+        /** @var MockInterface $transporter */
+        $transporter = $container->get(JsonRpcTransporter::class);
+        $transporter->shouldReceive('setLoadBalancer')
+            ->andReturnSelf();
+        $transporter->shouldReceive('send')
+            ->andReturnUsing(function ($data) {
+                $id = json_decode($data, true)['id'];
+                return json_encode([
+                    'id' => $id,
+                    'result' => null,
+                ]);
+            });
+        $factory = new ProxyFactory();
+        $proxyClass = $factory->createProxy(CalculatorServiceInterface::class);
+        /** @var CalculatorServiceInterface $service */
+        $service = new $proxyClass($container, CalculatorServiceInterface::class, 'jsonrpc');
+        $ret = $service->getString();
+        $this->assertNull($ret);
+    }
+
     public function testProxyCallableParameterAndReturnArray()
     {
         $container = $this->createContainer();

src/rpc-client/src/ServiceClient.php

@@ -58,6 +58,10 @@ class ServiceClient extends AbstractServiceClient
         $response = $this->checkRequestIdAndTryAgain($response, $id);
         if (array_key_exists('result', $response)) {
             $type = $this->methodDefinitionCollector->getReturnType($this->serviceInterface, $method);
+            if ($type->allowsNull() && $response['result'] === null) {
+                return null;
+            }
+
             return $this->normalizer->denormalize($response['result'], $type->getName());
         }