Any way to evaluate a cached task programmatically?

[seroperson]

Hello! Currently I'm developing a play-like live reloading plugin, which allows you to run application and then replace a classloader in runtime with updated code when source files change. I've implemented a task, which watches for filesystem changes and calls compile() method from JavaModule to compile classes and get the new classpath. However, when I change source files and then call compile() in runtime for the second time, which must compile changed files, it does nothing.

My task looks like this:

trait LiveReloadModule extends JavaModule:

  def liveReloadRun(args: Task[Args] = Task.Anon(Args())): Command[Unit] = Task.Command {
    // ...
    val reloadTrigger = () => {
      val result = compile()
      result.classes
    }

    Jvm.withClassLoader(
      classPath = runClasspath().map(_.path).toVector
    ) { classloader =>
      // start live-reloaded application, which triggers `reloadTrigger` when necessary
      // to compile changes and update the underlying classloader
      
      // ... blocking until some condition
    }
  }

How to do it correctly? I guess I need something like this to be possible:

compile() // compile code for the first time
// change source files
compile() // compile changed sources

[lihaoyi]

If you want to dynamically trigger task evaluation at runtime, the best way is probably to take an evaluator in your command and use that https://mill-build.org/mill/fundamentals/bundled-libraries.html#_evaluator_experimental

[seroperson]

Thank you! It partially works, at least I managed to make my tests green. But now there is another problem:

I've replaced my direct compile() call with something like evaluator.evaluate(Seq(s"${path}.compile")). When I directly called compile() task, it's being called on a necessary module "automatically", but now seems like I have to calculate path somehow. I see there is moduleCtx field, which have segments under the hood, and it's probably what I need to use, but it's an internal hidden API. Is there any way to call the exact compile task in current module?

[lihaoyi]

I think you can do evaluator.execute(compile) if you already know what task you want without needing to go through query resolution