Make composer/io part of the activate plugin API rather than constructor args

src/Composer/Plugin/PluginInterface.php

@@ -13,6 +13,7 @@
 namespace Composer\Plugin;
 
 use Composer\Composer;
+use Composer\IO\IOInterface;
 
 /**
  * Plugin interface
@@ -23,6 +24,9 @@ interface PluginInterface
 {
     /**
      * Apply plugin modifications to composer
+     *
+     * @param Composer $composer
+     * @param IOInterface $io
      */
-    public function activate();
+    public function activate(Composer $composer, IOInterface $io);
 }

src/Composer/Plugin/PluginManager.php

@@ -66,7 +66,7 @@ class PluginManager
     public function addPlugin(PluginInterface $plugin)
     {
         $this->plugins[] =  $plugin;
-        $plugin->activate();
+        $plugin->activate($this->composer, $this->io);
 
         if ($plugin instanceof EventSubscriberInterface) {
             $this->composer->getEventDispatcher()->addSubscriber($plugin);
@@ -139,11 +139,11 @@ class PluginManager
                 self::$classCounter++;
             }
 
-            $plugin = new $class($this->composer, $this->io);
-
             if ($oldInstallerPlugin) {
+                $installer = new $class($this->composer, $this->io);
                 $this->composer->getInstallationManager()->addInstaller($installer);
             } else {
+                $plugin = new $class();
                 $this->addPlugin($plugin);
             }
         }

tests/Composer/Test/Plugin/Fixtures/plugin-v1/Installer/Plugin.php

@@ -3,13 +3,14 @@
 namespace Installer;
 
 use Composer\Composer;
+use Composer\IO\IOInterface;
 use Composer\Plugin\PluginInterface;
 
 class Plugin implements PluginInterface
 {
     public $version = 'installer-v1';
 
-    public function activate()
+    public function activate(Composer $composer, IOInterface $io)
     {
     }
 }

tests/Composer/Test/Plugin/Fixtures/plugin-v2/Installer/Plugin2.php

@@ -3,13 +3,14 @@
 namespace Installer;
 
 use Composer\Composer;
+use Composer\IO\IOInterface;
 use Composer\Plugin\PluginInterface;
 
 class Plugin2 implements PluginInterface
 {
     public $version = 'installer-v2';
 
-    public function activate()
+    public function activate(Composer $composer, IOInterface $io)
     {
     }
 }

tests/Composer/Test/Plugin/Fixtures/plugin-v3/Installer/Plugin2.php

@@ -3,13 +3,14 @@
 namespace Installer;
 
 use Composer\Composer;
+use Composer\IO\IOInterface;
 use Composer\Plugin\PluginInterface;
 
 class Plugin2 implements PluginInterface
 {
     public $version = 'installer-v3';
 
-    public function activate()
+    public function activate(Composer $composer, IOInterface $io)
     {
     }
 }

tests/Composer/Test/Plugin/Fixtures/plugin-v4/Installer/Plugin1.php

@@ -3,6 +3,7 @@
 namespace Installer;
 
 use Composer\Composer;
+use Composer\IO\IOInterface;
 use Composer\Plugin\PluginInterface;
 
 class Plugin1 implements PluginInterface
@@ -10,7 +11,7 @@ class Plugin1 implements PluginInterface
     public $name = 'plugin1';
     public $version = 'installer-v4';
 
-    public function activate()
+    public function activate(Composer $composer, IOInterface $io)
     {
     }
 }

tests/Composer/Test/Plugin/Fixtures/plugin-v4/Installer/Plugin2.php

@@ -3,6 +3,7 @@
 namespace Installer;
 
 use Composer\Composer;
+use Composer\IO\IOInterface;
 use Composer\Plugin\PluginInterface;
 
 class Plugin2 implements PluginInterface
@@ -10,7 +11,7 @@ class Plugin2 implements PluginInterface
     public $name = 'plugin2';
     public $version = 'installer-v4';
 
-    public function activate()
+    public function activate(Composer $composer, IOInterface $io)
     {
     }
 }

tests/Composer/Test/Plugin/PluginInstallerTest.php

@@ -77,7 +77,7 @@ class PluginInstallerTest extends \PHPUnit_Framework_TestCase
     public function testInstallNewPlugin()
     {
         $this->repository
-            ->expects($this->once())
+            ->expects($this->exactly(2))
             ->method('getPackages')
             ->will($this->returnValue(array()));
         $installer = new PluginInstaller($this->io, $this->composer);
@@ -92,7 +92,7 @@ class PluginInstallerTest extends \PHPUnit_Framework_TestCase
     public function testInstallMultiplePlugins()
     {
         $this->repository
-            ->expects($this->once())
+            ->expects($this->exactly(2))
             ->method('getPackages')
             ->will($this->returnValue(array()));
         $installer = new PluginInstaller($this->io, $this->composer);
@@ -110,7 +110,7 @@ class PluginInstallerTest extends \PHPUnit_Framework_TestCase
     public function testUpgradeWithNewClassName()
     {
         $this->repository
-            ->expects($this->once())
+            ->expects($this->exactly(3))
             ->method('getPackages')
             ->will($this->returnValue(array($this->packages[0])));
         $this->repository
@@ -129,7 +129,7 @@ class PluginInstallerTest extends \PHPUnit_Framework_TestCase
     public function testUpgradeWithSameClassName()
     {
         $this->repository
-            ->expects($this->once())
+            ->expects($this->exactly(3))
             ->method('getPackages')
             ->will($this->returnValue(array($this->packages[1])));
         $this->repository