Class.forName can't find classes in sbt-1.3.0-RC1

[xerial]

steps

I'm still trying to find a reproduction, but basically, a problem happens when using Spark 2.4.x with Scala 2.11, sbt-1.3.0-RC1.

problem

• Call a method in a dependent library that uses Class.forName("(class name)") -> causes java.lang.ClassNotFoundException
• Call Class.forName("(class name)") works without any problem.

I guess some method (e.g., ClassLoader.getClassLoader(caller)) used in Class.forName has an issue in sbt-1.3.0-RC1's layered class loader:

   @CallerSensitive
    public static Class<?> forName(String className)
                throws ClassNotFoundException {
        Class<?> caller = Reflection.getCallerClass();
        return forName0(className, true, ClassLoader.getClassLoader(caller), caller);
    }

expectation

• There has been no problem until sbt 1.2.8

notes

• It seems a workaround is using Class.forName(name, true, Thread.currentThread().getContextClassLoader()) instead of Class.forName(name)
• Spark is unrelated (fixed the description)

sbt version: 1.3.0-RC1

[eed3si9n]

@xerial Thanks the report.

It seems a workaround is using Class.forName(name, true, Thread.currentThread().getContextClassLoader()) instead of Class.forName(name)

I think @eatkins is working on a workaround along the same lines, but built-in to our layered ClassLoader so you won't have to do it.

[eatkins]

See #4769.