Merge pull request #111 from proophsoftware/feature/stop_dispatch_with_preprocessor

Allow a preprocessor to stop dispatch

Author: Alexander Miertsch

examples/PrototypingFlavour/Messaging/CommandWithCustomHandler.php

@@ -0,0 +1,28 @@
+<?php
+/**
+ * This file is part of the proophsoftware/event-machine.
+ * (c) 2017-2018 prooph software GmbH <[email protected]>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+declare(strict_types=1);
+
+namespace ProophExample\PrototypingFlavour\Messaging;
+
+use Prooph\EventMachine\EventMachine;
+use Prooph\EventMachine\EventMachineDescription;
+use Prooph\EventMachine\JsonSchema\JsonSchema;
+
+final class CommandWithCustomHandler implements EventMachineDescription
+{
+    public const CMD_DO_NOTHING = 'DoNothing';
+    public const NO_OP_HANDLER = 'NoOpHandler';
+
+    public static function describe(EventMachine $eventMachine): void
+    {
+        $eventMachine->registerCommand(self::CMD_DO_NOTHING, JsonSchema::object(['msg' => JsonSchema::string()]));
+        $eventMachine->preProcess(self::CMD_DO_NOTHING, self::NO_OP_HANDLER);
+    }
+}

src/EventMachine.php

@@ -87,6 +87,8 @@ final class EventMachine implements MessageDispatcher, AggregateStateStore
     const SERVICE_ID_JSON_SCHEMA_ASSERTION = 'EventMachine.JsonSchemaAssertion';
     const SERVICE_ID_FLAVOUR = 'EventMachine.Flavour';
 
+    const CMD_METADATA_STOP_DISPATCH = 'EVENT-MACHINE-STOP-DISPATCH';
+
     /**
      * Map of command names and corresponding json schema of payload
      *
@@ -539,6 +541,10 @@ public function dispatch($messageOrName, array $payload = []): ?Promise
                     }
 
                     $messageOrName = $this->flavour()->callCommandPreProcessor($preProcessorOrStr, $messageOrName);
+
+                    if ($messageOrName->metadata()[self::CMD_METADATA_STOP_DISPATCH] ?? false) {
+                        return null;
+                    }
                 }
 
                 $bus = $this->container->get(self::SERVICE_ID_COMMAND_BUS);

tests/EventMachinePrototypingFlavourTest.php

@@ -11,13 +11,18 @@
 
 namespace Prooph\EventMachineTest;
 
+use Prooph\Common\Messaging\Message as ProophMessage;
+use Prooph\EventMachine\Commanding\CommandPreProcessor;
+use Prooph\EventMachine\Container\EventMachineContainer;
 use Prooph\EventMachine\EventMachine;
+use Prooph\EventMachine\Messaging\Message;
 use Prooph\EventMachine\Messaging\MessageDispatcher;
 use Prooph\EventMachine\Persistence\DocumentStore;
 use Prooph\EventMachine\Runtime\Flavour;
 use Prooph\EventMachine\Runtime\PrototypingFlavour;
 use ProophExample\PrototypingFlavour\Aggregate\UserDescription;
 use ProophExample\PrototypingFlavour\Aggregate\UserState;
+use ProophExample\PrototypingFlavour\Messaging\CommandWithCustomHandler;
 use ProophExample\PrototypingFlavour\Messaging\MessageDescription;
 use ProophExample\PrototypingFlavour\ProcessManager\SendWelcomeEmail;
 use ProophExample\PrototypingFlavour\Projector\RegisteredUsersProjector;
@@ -83,4 +88,47 @@ public function it_throws_exception_if_config_should_be_cached_but_contains_clos
 
         $eventMachine->compileCacheableConfig();
     }
+
+    /**
+     * @test
+     */
+    public function it_stops_dispatch_if_preprocessor_sets_metadata_flag()
+    {
+        $eventMachine = new EventMachine();
+
+        $eventMachine->load(CommandWithCustomHandler::class);
+
+        $noOpHandler = new class() implements CommandPreProcessor {
+            private $msg;
+
+            /**
+             * {@inheritdoc}
+             */
+            public function preProcess(ProophMessage $message): ProophMessage
+            {
+                if ($message instanceof Message) {
+                    $this->msg = $message->get('msg');
+                }
+
+                return $message->withAddedMetadata(EventMachine::CMD_METADATA_STOP_DISPATCH, true);
+            }
+
+            public function msg(): ?string
+            {
+                return $this->msg;
+            }
+        };
+
+        $eventMachine->initialize(new EventMachineContainer($eventMachine));
+
+        $eventMachine->bootstrapInTestMode([], [
+            CommandWithCustomHandler::NO_OP_HANDLER => $noOpHandler,
+        ]);
+
+        $eventMachine->dispatch(CommandWithCustomHandler::CMD_DO_NOTHING, [
+            'msg' => 'test',
+        ]);
+
+        $this->assertEquals('test', $noOpHandler->msg());
+    }
 }