Question

This is my composer.json file:

"require": {
    "php": ">=5.4",
    "zendframework/zendframework": "2.*",
    "doctrine/doctrine-module": "dev-master",
    "doctrine/doctrine-orm-module": "0.*",
    "gedmo/doctrine-extensions": "dev-master"
},
"require-dev": {
    "phpunit/phpunit": "3.7.*"
},
"scripts": {
    "post-update-cmd": [
        "rm -rf vendor/Behat",
        "git clone git://github.com/Behat/Behat.git",
        "cp composer.phar Behat/composer.phar",
        "cd Behat && git submodule update --init",
        "cd Behat && php composer.phar install",
        "cd Behat && php composer.phar require guzzle/guzzle:3.0.*",
        "mv Behat vendor/Behat",
        "ln -sf ../Behat/bin/behat vendor/bin/"
    ]
}

How can I make it so the scripts are only run in the dev environment?

Basically I want the scripts to run only when I call:

php composer.phar update --dev

Answer 1

To do the non-development environment update without triggering any scripts, use the --no-scripts command line switch for the update command:

php composer.phar update --no-scripts
                         ^^^^^^^^^^^^

By default, Composer scripts are only executed¹ in the base package². So you could have one package for development and in the live environment make it a dependency of the live system.

Apart from that, I do not see any way to differentiate scripts automatically.

---

This answer is back from 2012, the additional options in order of appearance can now safely be listed. As the list is composer-only and the original question smells to fall for x/y, the general answer is to use a build manager.

But turns out this could be done already at the day of asking, as in this composer-json example:

{
  "scripts": {
    "post-update-cmd": "composer::dev-post-update-cmd",
    "dev-post-update-cmd": [
      "rm -rf vendor/Behat",
      ": ... ",
      "ln -sf ../Behat/bin/behat vendor/bin/"
    ]
  }
}

• 1.0.0-alpha6 (2012-10-23): dispatch dev-only scripts with PHP script class and __callStatic, e.g. composer::dev-post-update-cmd. if in_array('--dev', $_SERVER['argv']) then $eventDispatcher->dispatchCommandEvent($name).
• 1.0.0-alpha7 (2013-05-04): --dev is now default and henceforth optional, --no-dev required for not --dev script dispatching. this effectively changes the command-line in question from: composer update --dev running only to: not running on composer update --no-dev. $event->isDevMode() now available, also required for new second parameter on dispatching the script on the event dispatcher. Compare with answer by Christian Koch.
• 1.0.0-alpha9 (2014-12-07): autoload-dev now allows to not have the script class in --no-dev automatically by removing it from autoload. this works b/c non-existing classes fall-through w/o error.
• 1.3.0-RC (2016-12-11): --dev is deprecated. COMPOSER_DEV_MODE environment parameter now available in update/install/dumpautoload scripts. no inherit need any longer for the PHP script class, unless enviroment parameters do not work in your setup, then use a PHP class script for a workaround. Compare with answer by Veda.
• 3 (future): --dev will needlessly make composer fatal, at least this is announced. this closes the circle to pre-1.0.0-alpha7 which also failed on the opposite, --no-dev. the command-line library in use then and yet in the future is not able to cope with -[-not]-args symmetrically, and if the pair is divided and one must go, then it can only throw.

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References

1. See "Note:" in What is a script? – Scripts – Composer Docs
2. Base package is commonly referred to as root package in the Composer documentation.