Reuses all jars to create an Scala instance if and only if all of them exist.

This is done mainly by performance reasons, since dependency resolution is not in the scope of what bloop is supposed to do. All resolution should be done by the user.

When this is not the case, we resolve the Scala jars from coursier. This is good because it means that if for some reason the scala jars do not exist, the user will get no matter what get the right instance. If the jars don't exist and they cannot be resolved, users will get a resolution error instead of a weird compilation error when compilation via Zinc starts.

Returns the default scala instance that is used in bloop's classloader.

A Scala instance is always required to compile with Zinc. As a result, Java projects that have no Scala configuration and want to be able to re-use Zinc's Javac infrastructure for incremental compilation need to have a dummy Scala instance available.

This method is responsible for creating this dummy Scala instance. The instance is fully functional and the jars for the instance come from Bloop class loader which depends on all the Scala jars. Here we get the jars that are usually used in scala jars from the protected domain of every class.

This could not work in case a user has set a strict security manager in the environment in which Bloop is running at. However, this is unlikely because Bloop will run on different machines that normal production-ready machines. In these machines, security managers don't usually exist and if they do don't happen to be so strict as to prevent getting the location from the protected domain.