[1.16] [FG4] Strange bug about accessing to class from different places

[hohserg]

I found a strange bug that can be reproduced by steps:

Create empty gradle project(without any plugins) (by intellij idea)

Create submodule `app` which contain regular forge mdk

Create submodule `common` which contain annotation `Mark` and class `ClassFromSubmodule` 

Create submodule `annotation-processor` which contain anootation processor which generate simple companion class for each class annotated with `@Mark`

Add some code:

//Test.java, `app` submodule
//annotation processor will generate TestCompanion for it(and he doing it)
@Mark
public class Test {
}


//Main.java, `app` submodule
@Mod("strange_bug")
public class Main {
    public Main() {
        try {
            System.out.println("Main successful: " + Class.forName("hohserg.strange.bug.TestCompanion"));
        } catch (ClassNotFoundException e) {
            System.out.println("Main failed: ");
            e.printStackTrace();
        }
      
        ClassFromSubmodule.test();
    }
}

//ClassFromSubmodule.java, `common` submodule
public class ClassFromSubmodule {
    public static void test() {
        try {
            System.out.println("ClassFromSubmodule successful: " + Class.forName("hohserg.strange.bug.TestCompanion"));
        } catch (Throwable e) {
            System.out.println("ClassFromSubmodule failed: ");
            e.printStackTrace();
        }
    }
}
	

Run `gradle :app:genIntellijRuns`

Try run client

Got follow log (time mark removed):

[modloading-worker-0/INFO] [STDOUT/]: [hohserg.strange.bug.Main:<init>:9]: Main successful: class hohserg.strange.bug.TestCompanion
[modloading-worker-0/INFO] [STDOUT/]: [hohserg.strange.bug.ClassFromSubmodule:test:8]: ClassFromSubmodule failed: 
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: java.lang.ClassNotFoundException: hohserg.strange.bug.TestCompanion
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:355)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at java.lang.Class.forName0(Native Method)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at java.lang.Class.forName(Class.java:264)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at hohserg.strange.bug.ClassFromSubmodule.test(ClassFromSubmodule.java:6)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at hohserg.strange.bug.Main.<init>(Main.java:14)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at java.lang.Class.newInstance(Class.java:442)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at net.minecraftforge.fml.javafmlmod.FMLModContainer.constructMod(FMLModContainer.java:81)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at net.minecraftforge.fml.ModContainer.lambda$buildTransitionHandler$4(ModContainer.java:120)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at java.util.concurrent.CompletableFuture$AsyncRun.run$$$capture(CompletableFuture.java:1640)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at java.util.concurrent.CompletableFuture$AsyncRun.run(CompletableFuture.java)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at java.util.concurrent.CompletableFuture$AsyncRun.exec(CompletableFuture.java:1632)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
[modloading-worker-0/INFO] [STDERR/]: [hohserg.strange.bug.ClassFromSubmodule:test:9]: 	at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)

So, class which generated by annotation processor is accessible from Main class(main class of mod) and isn't accessible from class from submodule.

Bug is preserved in built jar of mod if it's added as dependency to another mdk project.

Bug isn't preserved in built jar of mod if it's running at regular game client.

I checked, it's bug does not appears if `app` submodule is simply java application (without mdk)

I checked some other cases and resultative limits of bug:

Attempt to access to class which generated by annotation processor by `Class.forName` from class from other submodule in dev workspace perform `ClassNotFoundException` 

Running game with `.\StrangeBugRoot\gradlew.bat --project-dir ./StrangeBugRoot/ :app:runClient` does not produce bug.

Full source code:

https://github.com/hohserg1/StrangeBug

Edited June 19, 2021 by hohserg