Drush 9 features a deep rewrite of our app, both user facing and internals. We created and open sourced AnnotatedCommand, OutputFormatters, and Config. We leveraged Symfony Console for our CLI fundmentals. For details on Drush9, see the video or slides from our Drupalcon Vienna presentation.
** ADD AN ANNOTATED COMMAND EXAMPLE **
Unfortunately, old commandfiles such as example.drush.inc no longer load in Drush 9. We've made it relatively painless to port this code to Drush 9:
** ADD A GIF OF GENERATOR **
- Using Drush 9 on a working site, run
drush generate drush-command-file
.generate
is a wrapper for the Drupal Code Generator