After ugrading all my plugins to 2021.* and using gradle, I have this problem:
is compiled successfully, but on runtime I get
So I added
And it solves the problem, But I did it without understand why, what is the principle ?
com.intellij.openapi.compiler.CompileTask is part of the openapi, How can I guess that com.intellij.java is needed ? How do I know for other used classes what plugin is needed ?