On Sunday I did my first live stream where I upgraded my personal site to Drupal 9. It was a fun experience and I learned a few things – both for streaming and upgrading.
I managed to deploy a broken version of my site because I blindly trusted Composer metadata would prevent incompatible modules from allowing Drupal 9 to install. I was wrong. I forgot to use the Upgrade Status module to check if all of my contrib modules were compatible. I forgot to test the deploy and upgrade locally. 🤦♂️ Oops. Everything is fine, now. I had to make a fork of Disqus and Media Entity Browser.
Upgrading to Drupal 9
The biggest blocker I had was
drupal/console. Drupal Console is not compatible with Drupal 9, and you must remove it when trying to upgrade. You also need Drush 10, but that’s an easy change to make.