Install mill:
sudo curl -L -o /usr/local/bin/mill https://github.com/lihaoyi/mill/releases/download/0.1.1/0.1.1 && sudo chmod +x /usr/local/bin/mill
Generate IDEA project:
mill.scalalib.GenIdeaModule/idea
There is ivy"org.java-websocket:Java-WebSocket:1.3.7" in build.sc, but when generate IDEA files by mill mill.scalalib.GenIdeaModule/idea, the generated library xml file doesn't contain it, see .idea/libraries/(they are added to git)
Update: it seems a random issue, since it successfully generated the Java-WebSocket file after several tryings.