Appropriate solution for Drupal 8.4

[iainhouston]

Would value ability to install Drush 9 as required by Drupal 8.4 .... adopt Christopher Hopper's solution if appropriate?

Our production site is saying that we should update to Drupal 8.4.3 but we're finding all sorts of incompatibility issues with PHP version / Drush version / Drupal core version / contrib modules that seem to fall outside the control of Composer and need thorough investigation in our Drupal-vm systems.

I tried

    # Override Geoff's Drush install defaults
    # Install from source (git clone + composer-based install).
    drush_install_from_source: yes 
    drush_version: "master"
    drush_keep_updated: yes
    drush_force_update: yes
    drush_force_composer_install: yes

but I get Drush 8.1.15 instead of Drush 9 and of course, this doesn't account properly for drush global / site-local use of Drush 9.

[iainhouston]

I find only this combination works for Drupal 8.4.3

               Old                New                
PHP VM         7.1.12             7.1.12              
PHP Host       7.1.12             7.1.12
Drush VM       8.1.16-dev         ~9.0     
Drush Host     8.1.15             ~9.0            
Drupal Core    8.3.7              8.4.3
MySQL          5.7.20             5.7.20   (Required MySQL 5.5.3/MariaDB 5.5.20)

[geerlingguy]

This is a... complicated question, and one I'm currently working on myself for a number of different sites :(

Please also see:

• Drush install for Drupal 8.4+ and Drush 9 #41
• Drush 9 cannot SSH into Drupal VM drupal-vm#1595

[geerlingguy]

So I've kind of hedged my bets; this role now installs Drush one of three ways (Phar install is no longer an option):

1. drush_launcher_install: yes (default): Installs the Drush Launcher globally. The idea being that each of your Drupal projects would have it's own Drush dependency installed/used via Launcher. This seem to be the preferred way of things for Drush 9+.
2. drush_composer_global_install: yes (off by default): Installs Drush via Composer 'globally' (global to the user who did the install...). This is helpful in some cases, but slightly more annoying than phar global install, and a little slower.
3. drush_install_from_source: yes (off by default): Installs Drush globally via git clone, then installs Drush dependencies via Composer. Use only if you need bleeding edge or some exotic version that's not available via Composer, or if you need it system-wide globally. Note that this setup may not jive wonderfully if you're using Drush 9+ (in that case use the Launcher, I think).

I'm defaulting to #1 and will try to steer Drupal VM usage in that direction too. I'll have to figure out how to handle Drush Aliases though—they've changed a bit in Drush 9.

[geerlingguy]

(These features are in the totally revamped geerlingguy.drush 3.0.0 role.