FIX Use composer update for prefer-lowest

config/base.yml

@@ -127,7 +127,11 @@ before_script:
   - if [[ $(composer validate 2>&1 | tr '\n' ' ') =~ ' is valid' ]]; then cat composer.json; fi
 
   # Install with --prefer-source to ensure that admin javascript (which has export-ignore in .gitattributes) is installed so that NPM_TEST works properly
-  - composer install --prefer-source --no-interaction --no-progress --optimize-autoloader --verbose --profile $COMPOSER_INSTALL_ARG
+  # Modules do not have composer.lock files, so `composer install` is faster than `composer update`, however
+  # --prefer-lowest is only supported by `composer update`, not `composer install`
+  - COMPOSER_COMMAND=install
+  - if [ "$COMPOSER_INSTALL_ARG" == "--prefer-lowest" ]; then COMPOSER_COMMAND=update; fi
+  - composer $COMPOSER_COMMAND --prefer-source --no-interaction --no-progress --optimize-autoloader --verbose --profile $COMPOSER_INSTALL_ARG
   - composer show
 
   # Remove vendor unit tests files that were installed because of the use of --prefer-source