[SOLVED] [1.17.1] Error when trying to use :runClient / java.lang.StringIndexOutOfBoundsException: begin 0, end -1, lenght 3

[CheckerMark79]

After having a conversation with SizableShrimp in the Forge Discord I wanted to aks for help on the forums.

My mod works completely fine, it compiles fine, genIntellijRuns works fine, but every time I try to use :runClient I experience this error: https://pastebin.com/ekaF1MBL

What I have been told is that it is trying to load the eez class from the client-extra.jar. Someone else with a similiar issue deleted all the classes in this .jar and which fixed the issue, but I'm still getting the same error after deleting those classes.

I already did things like invalidate caches, and tried to add this to runs in the build.gradle: property 'legacyClassPath', '{minecraft_classpath}' but nothing works.

I also tried to run the latest MDK without changing any code but got the same error.

 

Does anyone else have an idea what I need to do? Or is this an issue on Forge's side that I need to report on GitHub?

Edited July 26, 2021 by CheckerMark79
Solved issue.

[CheckerMark79]

Alright, thanks to someone from the Forge Discord I managed to solve the issue.

If anyone ever gets this error: java.lang.RuntimeException: java.lang.StringIndexOutOfBounds: begin 0, end -1, length 3

Delete the client-extra.jar, found under external libraries, and refresh your gradle.

Also make sure you are using Java 16 (As of 1.17+)

This solved the issue for me, which took me days.