Switch from Drupal to Drupal Composer Managed Upstream Doc Update

[Adrianm6254]

Re: Switch from Drupal to Drupal Composer Managed Upstream

Priority: Low/Medium/High (choose one, remove the other options)

Issue Description:

The document fails to directly deal with the Drupal9 upstream itself.

THe Drupal 9 upstream that I used when upgrading from Drupal 8 moved the contrib modules/themes to the composer folder. When I tried to upgrade to the Pantheon Managed Composer Upstream it failed. When I tried using the auto-conflict resolution it moved everything from composer to contrib and then re-wrote my composer.json to a default when rendered my site unusable with no indication as to what was wrong.

It wasn't until I pulled my code down locally before I could see what had happened. After struggling for a full day to figure all of this out and I was finally able to get things working by manually taking the default composer.json and my working composer.json file and creading a composer.json that would not delete all my modules.

You should warn people of this apparent requirement BEFORE doing the upgrade.

If I have this wrong, please include what one should do when working with this apparent non-standard composer build because this is somehting YOU instituted when I first upgraded from Drupal 8.

Suggested Resolution

[rachelwhitton]

Might also relate to #8779 and #8706 and #8583