Allow ModuleClassLoader to optionally delegate class-loading to parent

[shartte]

The goal is to add a new entrypoint to https://github.com/McModLauncher/bootstraplauncher for JUnit runners, which disables classloader isolation. This change adds the needed constructor to ModuleClassLoader to enable that.

This is used to allow test-classes to live in the GAME layer, while still loading JUnit and other testing library classes found on the normal classpath. When being run by a unit testing framework, we do not control the JVM entrypoint like we normally do, and Gradle for example will class-load JUnit before calling any other hook. Our test classes need to refer to those same loaded classes, making it easier if isolation is disabled in such scenarios.

[marchermans]

So, principally, I understand this idea.
However, given that we usually do this with a filter instead of a blanket allow-all, I was wondering if you had any way of figuring out if such a filter was even possible in this case?

[shartte]

So, principally, I understand this idea. However, given that we usually do this with a filter instead of a blanket allow-all, I was wondering if you had any way of figuring out if such a filter was even possible in this case?

No since this should also apply to testing libraries added by users in userdev, and we cannot know those packages/libraries apriori.
In addition, this does not change anything about any environment other than the new JUnit environment. Only there will this take effect.

[marchermans]

I have thought about this for a while.

Allthough I am convinced that the JUnit API provides other, more standardized, ways of doing testing in a modularly isolated environment, right now we do not have the time.

As such this is at least a bridge and a gap to allow for this to work.

However, since I want to be clear that this should not be used in production, what so ever, I want a very load warning in the source code, in the form of previously mentioned annotations and documentation. As well as, a very loud warning in a log file!

Please add those and then this is good.