Pass the current dev mode to the event dispatcher, which in turn passes it to the events fired. This can be fetched in scripts to check which mode we are currently in

src/Composer/Installer.php

@@ -179,7 +179,7 @@ class Installer
         if ($this->runScripts) {
             // dispatch pre event
             $eventName = $this->update ? ScriptEvents::PRE_UPDATE_CMD : ScriptEvents::PRE_INSTALL_CMD;
-            $this->eventDispatcher->dispatchCommandEvent($eventName);
+            $this->eventDispatcher->dispatchCommandEvent($eventName, $this->devMode);
         }
 
         $this->suggestedPackages = array();
@@ -227,7 +227,7 @@ class Installer
             if ($this->runScripts) {
                 // dispatch post event
                 $eventName = $this->update ? ScriptEvents::POST_UPDATE_CMD : ScriptEvents::POST_INSTALL_CMD;
-                $this->eventDispatcher->dispatchCommandEvent($eventName);
+                $this->eventDispatcher->dispatchCommandEvent($eventName, $this->devMode);
             }
         }
 
@@ -487,7 +487,7 @@ class Installer
 
             $event = 'Composer\Script\ScriptEvents::PRE_PACKAGE_'.strtoupper($operation->getJobType());
             if (defined($event) && $this->runScripts) {
-                $this->eventDispatcher->dispatchPackageEvent(constant($event), $operation);
+                $this->eventDispatcher->dispatchPackageEvent(constant($event), $this->devMode, $operation);
             }
 
             // not installing from lock, force dev packages' references if they're in root package refs
@@ -516,7 +516,7 @@ class Installer
 
             $event = 'Composer\Script\ScriptEvents::POST_PACKAGE_'.strtoupper($operation->getJobType());
             if (defined($event) && $this->runScripts) {
-                $this->eventDispatcher->dispatchPackageEvent(constant($event), $operation);
+                $this->eventDispatcher->dispatchPackageEvent(constant($event), $this->devMode, $operation);
             }
 
             if (!$this->dryRun) {

src/Composer/Script/Event.php

@@ -37,18 +37,25 @@ class Event
      */
     private $io;
 
+    /**
+     * @var boolean Dev mode flag
+     */
+    private $devMode;
+
     /**
      * Constructor.
      *
      * @param string      $name     The event name
      * @param Composer    $composer The composer object
      * @param IOInterface $io       The IOInterface object
+     * @param boolean     $devMode  Whether or not we are in dev mode
      */
-    public function __construct($name, Composer $composer, IOInterface $io)
+    public function __construct($name, Composer $composer, IOInterface $io, $devMode)
     {
         $this->name = $name;
         $this->composer = $composer;
         $this->io = $io;
+        $this->devMode = $devMode;
     }
 
     /**
@@ -80,4 +87,14 @@ class Event
     {
         return $this->io;
     }
+
+    /**
+     * Return the dev mode flag
+     *
+     * @return boolean
+     */
+    public function isDevMode()
+    {
+        return $this->devMode;
+    }
 }

src/Composer/Script/EventDispatcher.php

@@ -55,21 +55,23 @@ class EventDispatcher
      * Dispatch a package event.
      *
      * @param string             $eventName The constant in ScriptEvents
+     * @param boolean            $devMode   Whether or not we are in dev mode
      * @param OperationInterface $operation The package being installed/updated/removed
      */
-    public function dispatchPackageEvent($eventName, OperationInterface $operation)
+    public function dispatchPackageEvent($eventName, $devMode, OperationInterface $operation)
     {
-        $this->doDispatch(new PackageEvent($eventName, $this->composer, $this->io, $operation));
+        $this->doDispatch(new PackageEvent($eventName, $this->composer, $this->io, $devMode, $operation));
     }
 
     /**
      * Dispatch a command event.
      *
-     * @param string $eventName The constant in ScriptEvents
+     * @param string  $eventName The constant in ScriptEvents
+     * @param boolean $devMode   Whether or not we are in dev mode
      */
-    public function dispatchCommandEvent($eventName)
+    public function dispatchCommandEvent($eventName, $devMode)
     {
-        $this->doDispatch(new CommandEvent($eventName, $this->composer, $this->io));
+        $this->doDispatch(new CommandEvent($eventName, $this->composer, $this->io, $devMode));
     }
 
     /**

src/Composer/Script/PackageEvent.php

@@ -34,11 +34,12 @@ class PackageEvent extends Event
      * @param string             $name      The event name
      * @param Composer           $composer  The composer objet
      * @param IOInterface        $io        The IOInterface object
+     * @param boolean            $devMode   Whether or not we are in dev mode
      * @param OperationInterface $operation The operation object
      */
-    public function __construct($name, Composer $composer, IOInterface $io, OperationInterface $operation)
+    public function __construct($name, Composer $composer, IOInterface $io, $devMode, OperationInterface $operation)
     {
-        parent::__construct($name, $composer, $io);
+        parent::__construct($name, $composer, $io, $devMode);
         $this->operation = $operation;
     }
 

tests/Composer/Test/Script/EventDispatcherTest.php

@@ -32,7 +32,7 @@ class EventDispatcherTest extends TestCase
             ->method('write')
             ->with('<error>Script Composer\Test\Script\EventDispatcherTest::call handling the post-install-cmd event terminated with an exception</error>');
 
-        $dispatcher->dispatchCommandEvent("post-install-cmd");
+        $dispatcher->dispatchCommandEvent("post-install-cmd", false);
     }
 
     /**
@@ -60,7 +60,7 @@ class EventDispatcherTest extends TestCase
             ->method('execute')
             ->with($command);
 
-        $dispatcher->dispatchCommandEvent("post-install-cmd");
+        $dispatcher->dispatchCommandEvent("post-install-cmd", false);
     }
 
     public function testDispatcherCanExecuteCliAndPhpInSameEventScriptStack()
@@ -95,7 +95,7 @@ class EventDispatcherTest extends TestCase
             ->with('Composer\Test\Script\EventDispatcherTest', 'someMethod')
             ->will($this->returnValue(true));
 
-        $dispatcher->dispatchCommandEvent("post-install-cmd");
+        $dispatcher->dispatchCommandEvent("post-install-cmd", false);
     }
 
     private function getDispatcherStubForListenersTest($listeners, $io)