This is a Composer-based installer for the Lightning Drupal distribution. Welcome to the future!
$ composer create-project acquia/lightning-project MY_PROJECT
Composer will create a new directory called MY_PROJECT containing a docroot directory with a full Lightning code base therein. You can then install it like you would any other Drupal site.
drush make, drush pm-download, drush pm-update and their ilk are the old-school way of maintaining your code base. Forget them. You're in Composer land now!
Let this handy table be your guide:
| Task | Drush | Composer |
|---|---|---|
| Installing a contrib project (latest version) | drush pm-download PROJECT |
composer require drupal/PROJECT |
| Installing a contrib project (specific version) | drush pm-download PROJECT-8.x-1.0-beta3 |
composer require drupal/PROJECT:1.0.0-beta3 |
| Installing a javascript library (e.g. dropzone) | drush pm-download dropzone |
composer require bower-asset/dropzone |
| Updating all contrib projects and Drupal core | drush pm-update |
composer update |
| Updating a single contrib project | drush pm-update PROJECT |
composer update drupal/PROJECT |
| Updating Drupal core | drush pm-update drupal |
composer update drupal/core |
The magic is that Composer, unlike Drush, is a dependency manager. If module foo version: 1.0.0 depends on baz version: 3.2.0, Composer will not let you update baz to 3.3.0 (or downgrade it to 3.1.0, for that matter). Drush has no concept of dependency management. If you've ever accidentally hosed a site because of dependency issues like this, you've probably already realized how valuable Composer can be.
But to be clear: it is still very helpful to use a site management tool like Drush or Drupal Console. Tasks such as database updates (drush updatedb) are still firmly in the province of such utilities. This installer will install a copy of Drush (local to the project) in the bin directory.
you can specify a version from the command line with:
$ composer require drupal/<modulename>:<version>
For example:
$ composer require drupal/ctools:3.0.0-alpha26
$ composer require drupal/token:1.x-dev
In these examples, the composer version 3.0.0-alpha26 maps to the drupal.org version 8.x-3.0-alpha26 and 1.x-dev maps to 8.x-1.x branch on drupal.org.
If you specify a branch, such as 1.x you must add -dev to the end of the version.
Composer is only responsible for maintaining the code base.
If you peek at the .gitignore we provide, you'll see that certain directories, including all directories containing contributed projects, are excluded from source control. This might be a bit disconcerting if you're newly arrived from Planet Drush, but in a Composer-based project like this one, you SHOULD NOT commit your installed dependencies to source control.
When you set up the project, Composer will create a file called composer.lock, which is a list of which dependencies were installed, and in which versions. Commit composer.lock to source control! Then, when your colleagues want to spin up their own copies of the project, all they'll have to do is run composer install, which will install the correct versions of everything in composer.lock.