Kotlin Class name starts with `$` has an incorrect Metadata

[fan87]

I haven't started parsing metadata yet, but I have placed some breakpoints inside Kotlin reflection, and it seemed like $ were replaced by . in the deserialized class metadata.

Version: 1.11-SNAPSHOT

Steps to Reproduce

1. Main.kt

fun main() {
    val c = `$ExampleClass`::class
    println(c.nestedClasses.joinToString(","))
}
object `$ExampleClass` {
    class Nested
}

2. Remap -> Shadow the remapped jar (reflect is required to be shaded into)

3. Run the jar java -cp loom-remap-issue-1.0-SNAPSHOT.jar MainKt

Expected Behavior

This is the expected result from the snippet provided above (without Fabric Loom remapping the Jar):

With Fabric Loom Remapping:

Notes

I can't and won't share why I needed $ to be the first character of the class name. It's because of a library we are using.

[fan87]

I have a temporary fix:

fabric-loom/src/main/kotlin/net/fabricmc/loom/kotlin/remapping/KotlinClassRemapper.kt

Line 89 in d6ff760

val remapped = remapper.map(name.toJvmInternalName()).replace('$', '.')

val normalizedName = name.replace('$', '\n')
val remapped = remapper.map(normalizedName.toJvmInternalName()).replace('$', '.').replace('\n', '$')

This would fix the issue, but I'm not certain if the name is expected to have $, if so, it could fail to remap some classes. However, I'm expecting the answer to be no, otherwise it could be a separate issue.

\n is a control character, and AFAIR JVM prohibits the use of control characters in class names, so it's a valid placeholder for the dollar sign character.

[Player3324]

the JVM has hardly any limitations, it's only the languages on top (like Java) and their libraries that might be picky.

See https://docs.oracle.com/javase/specs/jvms/se22/html/jvms-4.html#jvms-4.2.2

[modmuss50]

I think the fix above is good enough for now, it does mean you wont be able to correctly remap these classes but there is currently no need to do this.