Register ErrorHandler early to catch deprecation notices while the Application is being initialized

bin/composer

@@ -10,6 +10,7 @@ require __DIR__.'/../src/bootstrap.php';
 
 use Composer\Console\Application;
 use Composer\XdebugHandler\XdebugHandler;
+use Composer\Util\ErrorHandler;
 
 error_reporting(-1);
 
@@ -57,6 +58,8 @@ if (function_exists('ini_set')) {
 
 putenv('COMPOSER_BINARY='.realpath($_SERVER['argv'][0]));
 
+ErrorHandler::register();
+
 // run the command application
 $application = new Application();
 $application->run();

src/Composer/Console/Application.php

@@ -127,6 +127,8 @@ class Application extends BaseApplication
         $io = $this->io = new ConsoleIO($input, $output, new HelperSet(array(
             new QuestionHelper(),
         )));
+
+        // Register error handler again to pass it the IO instance
         ErrorHandler::register($io);
 
         if ($input->hasParameterOption('--no-cache')) {