return the upper-most event in chain

src/Composer/Script/Event.php

@@ -104,15 +104,30 @@ class Event extends BaseEvent
     }
 
     /**
-   * Get the originating event.
+     * Set the originating event.
      *
      * @param \Composer\EventDispatcher\Event $event
      * @return $this
      */
     public function setOriginatingEvent(BaseEvent $event)
     {
-      $this->originatingEvent = $event;
+      $this->originatingEvent = $this->calculateOriginatingEvent($event);
 
       return $this;
     }
+
+    /**
+     * Returns the upper-most event in chain.
+     *
+     * @param \Composer\EventDispatcher\Event $event
+     * @return \Composer\EventDispatcher\Event
+     */
+    private function calculateOriginatingEvent(BaseEvent $event)
+    {
+      if ($event instanceof Event && $event->getOriginatingEvent()) {
+        return $this->calculateOriginatingEvent($event->getOriginatingEvent());
+      }
+
+      return $event;
+    }
 }

tests/Composer/Test/Script/EventTest.php

@@ -0,0 +1,73 @@
+<?php
+
+
+namespace Composer\Test\Script;
+
+
+use Composer\Composer;
+use Composer\Config;
+use Composer\Script\Event;
+use Composer\Test\TestCase;
+
+class EventTest extends TestCase {
+
+  public function testEventSetsOriginatingEvent() {
+    $io = $this->getMockBuilder('Composer\IO\IOInterface')->getMock();
+    $composer = $this->createComposerInstance();
+
+    $originatingEvent = new \Composer\EventDispatcher\Event('originatingEvent');
+
+    $scriptEvent = new Event('test', $composer, $io, true);
+
+    $this->assertNull(
+      $scriptEvent->getOriginatingEvent(),
+      'originatingEvent is initialized as null'
+    );
+
+    $scriptEvent->setOriginatingEvent($originatingEvent);
+
+    $this->assertSame(
+      $originatingEvent,
+      $scriptEvent->getOriginatingEvent(),
+      'getOriginatingEvent() SHOULD return test event'
+    );
+
+  }
+
+  public function testEventCalculatesNestedOriginatingEvent() {
+    $io = $this->getMockBuilder('Composer\IO\IOInterface')->getMock();
+    $composer = $this->createComposerInstance();
+
+
+    $originatingEvent = new \Composer\EventDispatcher\Event('upperOriginatingEvent');
+    $intermediateEvent = new Event('intermediate', $composer, $io, true);
+    $intermediateEvent->setOriginatingEvent($originatingEvent);
+
+    $scriptEvent = new Event('test', $composer, $io, true);
+    $scriptEvent->setOriginatingEvent($intermediateEvent);
+
+    $this->assertNotSame(
+      $intermediateEvent,
+      $scriptEvent->getOriginatingEvent(),
+      'getOriginatingEvent() SHOULD NOT return intermediate events'
+    );
+
+    $this->assertSame(
+      $originatingEvent,
+      $scriptEvent->getOriginatingEvent(),
+      'getOriginatingEvent() SHOULD return upper-most event'
+    );
+
+  }
+
+  private function createComposerInstance()
+  {
+    $composer = new Composer;
+    $config = new Config;
+    $composer->setConfig($config);
+    $package = $this->getMockBuilder('Composer\Package\RootPackageInterface')->getMock();
+    $composer->setPackage($package);
+
+    return $composer;
+  }
+}