hello world cannot find main class, scala 3 project

[jake-miles]

Hello. I can't imagine this is an actual issue, more that if I'm just doing things incorrectly, so I thought I'd start here in Discussions.

Coming back to Scala to give it a try after a few years. I'd like to use Mill for a Scala 3 project but I can't get Hello World to run. The online docs for Mill are for Scala 2.

Is there a dead simple hello world for a Mill Scala 3 project anywhere on the web I could look at, or could someone just paste here what build.sc and the main file would a) contain, b) need to be named, c) need to be located relative to the project root?

For example, this cannot find the main class:

build.sc

import mill._, scalalib._

object devmap extends ScalaModule {
  def scalaVersion = "3.5.2"
}

This is the hello world from the official Scala site, with a package statement added:

src/hello/hello.scala

package hello

@main
def hello: Unit = 
  println("Hello world")

./mill hello
... snip ...
1 tasks failed
hello.finalMainClass No main class specified or found

$ $ find . out -name *.class
./out/mill-build/compile.dest/classes/build_/package_$hello$.class
./out/mill-build/compile.dest/classes/build_/package_$.class
./out/mill-build/compile.dest/classes/build_/MillMiscInfo.class
./out/mill-build/compile.dest/classes/build_/package_.class
./out/mill-build/compile.dest/classes/build_/MillMiscInfo$.class
out/mill-build/compile.dest/classes/build_/package_$hello$.class
out/mill-build/compile.dest/classes/build_/package_$.class
out/mill-build/compile.dest/classes/build_/MillMiscInfo.class
out/mill-build/compile.dest/classes/build_/package_.class
out/mill-build/compile.dest/classes/build_/MillMiscInfo$.class

I've also tried removing the package statement, same error.

Thanks for any help.

[jake-miles]

As I suspected, it was me. The issue was the path to hello.scala. It needed to be ./hello/src/hello.scala. I had it as ./src/hello/hello.scala.