added validate task, closes #81

src/Composer/Command/ValidateCommand.php

@@ -0,0 +1,56 @@
+<?php
+
+/*
+ * This file is part of Composer.
+ *
+ * (c) Nils Adermann <naderman@naderman.de>
+ *     Jordi Boggiano <j.boggiano@seld.be>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Composer\Command;
+
+use Composer\Repository\PlatformRepository;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Output\OutputInterface;
+use Composer\Json\JsonFile;
+
+/**
+ * @author Robert Schönthal <seroscho@googlemail.com>
+ */
+class ValidateCommand extends Command
+{
+    protected function configure()
+    {
+        $this
+            ->setName('validate')
+            ->setDescription('validates a composer.json')
+            ->setDefinition(array(
+                new InputArgument('file', InputArgument::OPTIONAL, 'path to composer.json file', getcwd().'/composer.json')
+            ))
+            ->setHelp(<<<EOT
+The validate command validates a given composer.json
+<info>php composer.phar validate</info> for current location
+or
+<info>php composer.phar validate /path/to/composer.json</info> for custom location
+
+EOT
+            )
+        ;
+    }
+
+    protected function execute(InputInterface $input, OutputInterface $output)
+    {
+        $file = $input->getArgument('file');
+
+        if (!is_readable($file)) {
+            throw new \InvalidArgumentException('composer.json not found '.$file);
+        }
+
+        $result = JsonFile::parseJson(file_get_contents($file));
+        $output->writeln('<info>valid</info> '.$file.' is valid');
+    }
+}

src/Composer/Console/Application.php

@@ -175,6 +175,7 @@ class Application extends BaseApplication
         $this->add(new Command\UpdateCommand());
         $this->add(new Command\DebugPackagesCommand());
         $this->add(new Command\SearchCommand());
+        $this->add(new Command\ValidateCommand());
 
         if ('phar:' === substr(__FILE__, 0, 5)) {
             $this->add(new Command\SelfUpdateCommand());