Add PRE_COMMAND_RUN event, fixes #7002

doc/articles/scripts.md

@@ -63,6 +63,9 @@ Composer fires the following named events during its execution process:
 - **pre-file-download**: occurs before files are downloaded and allows
   you to manipulate the `RemoteFilesystem` object prior to downloading files
   based on the URL to be downloaded.
+- **pre-command-run**: occurs before a command is executed and allows you to
+  manipulate the `InputInterface` object's options and arguments to tweak
+  a command's behavior.
 
 > **Note:** Composer makes no assumptions about the state of your dependencies
 > prior to `install` or `update`. Therefore, you should not specify scripts

src/Composer/Command/BaseCommand.php

@@ -15,8 +15,11 @@ namespace Composer\Command;
 use Composer\Composer;
 use Composer\Config;
 use Composer\Console\Application;
+use Composer\Factory;
 use Composer\IO\IOInterface;
 use Composer\IO\NullIO;
+use Composer\Plugin\PreCommandRunEvent;
+use Composer\Plugin\PluginEvents;
 use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Output\OutputInterface;
 use Symfony\Component\Console\Command\Command;
@@ -123,6 +126,14 @@ abstract class BaseCommand extends Command
      */
     protected function initialize(InputInterface $input, OutputInterface $output)
     {
+        // initialize a plugin-enabled Composer instance, either local or global
+        $composer = $this->getComposer(false, false);
+        if (null === $composer) {
+            $composer = Factory::createGlobal($this->getIO(), false);
+        }
+        $preCommandRunEvent = new PreCommandRunEvent(PluginEvents::PRE_COMMAND_RUN, $input);
+        $composer->getEventDispatcher()->dispatch($preCommandRunEvent->getName(), $preCommandRunEvent);
+
         if (true === $input->hasParameterOption(array('--no-ansi')) && $input->hasOption('no-progress')) {
             $input->setOption('no-progress', true);
         }

src/Composer/Plugin/PluginEvents.php

@@ -48,4 +48,14 @@ class PluginEvents
      * @var string
      */
     const PRE_FILE_DOWNLOAD = 'pre-file-download';
+
+    /**
+     * The PRE_COMMAND_RUN event occurs before a command is executed and lets you modify the input arguments/options
+     *
+     * The event listener method receives a
+     * Composer\Plugin\PreCommandRunEvent instance.
+     *
+     * @var string
+     */
+    const PRE_COMMAND_RUN = 'pre-command-run';
 }

src/Composer/Plugin/PreCommandRunEvent.php

@@ -0,0 +1,51 @@
+<?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\Plugin;
+
+use Composer\EventDispatcher\Event;
+use Symfony\Component\Console\Input\InputInterface;
+
+/**
+ * The pre command run event.
+ *
+ * @author Jordi Boggiano <j.boggiano@seld.be>
+ */
+class PreCommandRunEvent extends Event
+{
+    /**
+     * @var InputInterface
+     */
+    private $input;
+
+    /**
+     * Constructor.
+     *
+     * @param string         $name         The event name
+     * @param InputInterface $input
+     */
+    public function __construct($name, InputInterface $input)
+    {
+        parent::__construct($name);
+        $this->input = $input;
+    }
+
+    /**
+     * Returns the console input
+     *
+     * @return InputInterface
+     */
+    public function getInput()
+    {
+        return $this->input;
+    }
+}