Got a similar one.
Tried a lot o different versions.
Exception in thread "main" java.lang.RuntimeException: java.io.FileNotFoundException: C:\Users\VTM\.gradle\caches\minecraft\assets\indexes\{ASSET_INDEX}.json (The system cannot find the file specified)
at com.google.common.base.Throwables.propagate(Throwables.java:160)
at GradleStart.setupAssets(GradleStart.java:260)
at GradleStart.startClient(GradleStart.java:82)
at GradleStart.main(GradleStart.java:56)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)
Caused by: java.io.FileNotFoundException: C:\Users\VTM\.gradle\caches\minecraft\assets\indexes\{ASSET_INDEX}.json (The system cannot find the file specified)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.<init>(FileInputStream.java:146)
at java.io.FileReader.<init>(FileReader.java:72)
at GradleStart.loadAssetsIndex(GradleStart.java:266)
at GradleStart.setupAssets(GradleStart.java:204)
... 7 more
Process finished with exit code 1
Edit:
Running just
gradlew setupDecompWorkspace
Fixed it!
No need to clean before.