Using Drush on a Drupal 8 site installed via Composer I had a Drupal 8 project installed from Drupal 8 sources what had been downloaded from Drupal 8 site. Recently I heard a good thought that it would be more comfortable to have the project originally installed via Composer. I did the migration and now the project has a structure likewise installed via Composer. That is, it has the "web" subdirectory with Drupal 8 files, the "vendor" directory isn't included in Drupal files and so on.

The site worked successfully after migration.

However, I ran into a problem. Namely, after migration, I couldn't use Drush on the project. The following error appeared upon trying to execute a command "drush cr".

Command cache-rebuild needs a higher bootstrap level to run - you will need to invoke drush from a     [error]

more functional Drupal environment to run this command.
Command cache-rebuild requires Drupal core version 8+ to run.


My colleagues advised me to install Drush-launcher from GitHub as a shell for original Drush. I did it, this problem seemingly disappeared. But I ran into a next one. Namely, Now I can't use Drush for projects made on Drupal 7.

Could you clarify me, is it possible to set up original Drush for sites installed via Composer and without using the Drupal launcher?
Acquia Dev Desktop comes with Drush included, and I assume that you could just continue to use that for Drupal 7. However, since you installed Drush Launcher and are using it as drush (drush.bat), you are shadowing it. Break the shadowing by renaming one of the two.