Laravel: Undefined index: controllers_base_namespace

In ServiceProvider.php line 111: Undefined index: controllers_base_namespace

Issue

Starting with Laravel 6, you may now remove the namespace property from the RouteServiceProvider and register class-based routes or tuples instead. In Laravel 8, this became the default convention.

Upon switching to this convention, you may encounter this error if you have cached your routes using route:cache as the cached value and property no longer match.

Solution

You may resolve this issue by clearing your cache with the route:clear. However, due to this error, that command may not work. If not, you may forcibly remove the cached files from the bootstrap/cache folder by running rm -f bootstrap/cache/route*.php.