back up your existing drupal 9 composer.json
1. delete core/ and vendor/ directories. in my case, they are at, "web/core," and, "vendor," in the topmost directory.
2. delete composer.lock
3. run the new composer.json for drupal 10.
grab it from the .zip here: https://www.drupal.org/project/drupal/releases/10.0.0 → . Make sure to edit, "installer-paths," and, "locations" to match where your current code lives. My web-root is, "web." so My composer file would look like this:
"extra": {
"drupal-scaffold": {
"locations": {
"web-root": "./web"
}
},
"installer-paths": {
"web/core": [
"type:drupal-core"
],
"web/libraries/{$name}": [
"type:drupal-library"
],
4. after the initial composer install, run composer require for each of your modules in your backed up composer file. Don't add a version constraint:
composer require drupal/admin_toolbar -W
You may see some errors and you will have to address them as they come up.
good luck!
but I just replaced my composer.json with a vanilla drupal 10 composer.json.
I deleted the core and vendor directories and ran composer install.
I then composer required each of the modules I needed. You can string them together in a single command:
composer require drupal/project1 drupal/project2 drupal/project3 -W
Use the "-W," to include all the dependencies. Don't use a version constraint so it will just grab the version you need.
Run drush updb
This is a drastic approach but if you don't mind rolling through your site and looking for things that might be broken it will at least get you to Drupal 10.