`kotlinx.coroutines.debug`'s `module-info.java` is incorrect preventing any project using JPMS to use debug probes

[ArchangelX360]

Any usage of the kotlinx.coroutines.debug package, for example import kotlinx.coroutines.debug.DebugProbes results in:

[JAVA_MODULE_DOES_NOT_EXPORT_PACKAGE] Symbol is declared in module 'kotlinx.coroutines.debug' which does not export package 'kotlinx.coroutines.debug'

The split package between kotlinx.coroutines.core and kotlinx.coroutines.debug of package kotlinx.coroutines.debug must be solved and cannot be hacked around by commenting its exports statement in kotlinx.coroutines.debug's module-info.java 😢.

---

To continue the investigation, using custom module loading code, we merged kotlin.stdlib, kotlinx.coroutines.core and kotlinx.coroutines.debug modules at runtime:

• kotlinx.coroutines.core and kotlinx.coroutines.debug to mitigate the package split
• kotlin.stdlib to mitigate the circular dependency between kotlinx.coroutines.debug and kotlin.stdlib after bytebuddy injection at runtime
  • kotlin.stdlib --- (due to injected code) --> kotlinx.coroutines.debug -> kotlinx.stdlib

That provided us with a few more information about what is wrong with the current module-info.java:

1. some statements are missing (probably coming from the shadowing of bytebuddy):

requires com.sun.jna;
exports kotlinx.coroutines.repackaged.net.bytebuddy.agent to com.sun.jna;

2. these redundant (bytebuddy being shadowed in the same module) requires crashes at runtime:

requires net.bytebuddy.agent;
requires net.bytebuddy;

3. when used in production, the current declaration and structure of kotlinx-coroutines-debug jar forces users to bring in jars to their runtime module path to fulfill:

requires org.junit.jupiter.api;
requires org.junit.platform.commons;

JUnit is not something one would want in production runtime module path 😅...

---

I did not find any suitable workaround to unblock ourselves. The only solution I see is to:

• fix the split package of kotlinx.coroutines.debug package in kotlinx.coroutines.core and kotlinx.coroutines.debug (providing an additional jar for kotlinx-coroutines-debug with probably a new name like kotlinx-coroutines-debug2 😄)
• fix module-info.java issues pointed in point 1 and 2
• extract junit related utilities currently present in kotlinx.coroutines.debug.junit4 and kotlinx.coroutines.debug.junit5 packages into additional jars (e.g. kotlinx-coroutines-debug-junit4 and kotlinx-coroutines-debug-junit5), and remove requires statements of point 3

[dovchinnikov]

Related #3633