Deployment using Composer replacing old style install but issues with legacy Drush I took a Drupal project that was created awhile back via downloading a tar file and recreated it on a local via composer with drupal-project. 

The recommended files were committed to git (i.e. no contributed modules, etc.) and cloned on the server. The composer install was clean.

At the point of doing a $ drush sqlc to load the database, it became evident that there was an issue - Drush error message below. I believe the issue is that Drush was already installed. 

$ which drush outputs /home/me/.composer/vendor/bin/drush. 

The error message when I attempt to run drush sqlc or drush status from the project, even with --root, is the following. 


  PHP Warning:  require(/var/www/html/drupal/d8/vendor/composer/../../load.environment.php): failed to open stream: No such file or directory in /var/www/html/drupal/d8/vendor/composer/autoload_real.php on line 70
      PHP Stack trace:
      PHP   1. {main}() /var/www/html/drupal/d8/vendor/drush/drush/drush:0
      PHP   2. require() /var/www/html/drupal/d8/vendor/drush/drush/drush:4
      PHP   3. include_once() /var/www/html/drupal/d8/vendor/drush/drush/drush.php:56
      PHP   4. ComposerAutoloaderInit6220513682b217c143f76d07878222a3::getLoader() /var/www/html/drupal/d8/vendor/autoload.php:7
      PHP   5. composerRequire6220513682b217c143f76d07878222a3() /var/www/html/drupal/d8/vendor/composer/autoload_real.php:60
      PHP Fatal error:  require(): Failed opening required '/var/www/html/drupal/d8/vendor/composer/../../load.environment.php' (include_path='/var/www/html/drupal/d8/vendor/pear/pear_exception:/var/www/html/drupal/d8/vendor/pear/console_getopt:/var/www/html/drupal/d8/vendor/pear/pear-core-minimal/src:/var/www/html/drupal/d8/vendor/pear/archive_tar:.:/usr/share/php') in /var/www/html/drupal/d8/vendor/composer/autoload_real.php on line 70
      PHP Stack trace:
      PHP   1. {main}() /var/www/html/drupal/d8/vendor/drush/drush/drush:0
      PHP   2. require() /var/www/html/drupal/d8/vendor/drush/drush/drush:4
      PHP   3. include_once() /var/www/html/drupal/d8/vendor/drush/drush/drush.php:56
      PHP   4. ComposerAutoloaderInit6220513682b217c143f76d07878222a3::getLoader() /var/www/html/drupal/d8/vendor/autoload.php:7
      PHP   5. composerRequire6220513682b217c143f76d07878222a3() /var/www/html/drupal/d8/vendor/composer/autoload_real.php:60


In addition to Drush being in both ~/.composer/vendor and &lt;root&gt;/vendor, I note that ~/.composer contains

autoload.php
composer
phpdocumentor
phpunit
symfony
bin
doctrine
phpspec
sebastian


How do I go about cleaning this up so that the project root is the sole repository of these files and Drush can find what it's looking for?
As @Jaypan commented, globally you only need the Drush Launcher as phar file. And remove the old globally installed Drush version, this install method via composer global require is no longer supported. If you still need a legacy Drush version for other Drupal sites, download it the same way as phar file, see http://docs.drush.org/en/8.x/install. Which then can act as launcher by the way, so you don't need the Drush Launcher in this case.