First run, giberrish output?

[MathPlayer]

Hi,

I struggle to understand the mill output for the very beginning of my mill journey. Any help is appreciated. It's worthy to mention I dug enough through the docs without understanding my issue and how to solve it.

I am trying to use mill in my Scala projects.
I started with the latest wrapper, ./mill --version prints:

Mill Build Tool version 1.1.2
java.version: 21.0.9
java.vendor: Azul Systems, Inc.
java.home: /Users/<REDACTED>/Library/Caches/Coursier/arc/https/cdn.azul.com/zulu/bin/zulu21.46.19-ca-jdk21.0.9-macosx_aarch64.tar.gz/zulu21.46.19-ca-jdk21.0.9-macosx_aarch64/zulu-21.jdk/Contents/Home
file.encoding: UTF-8
os.name: Mac OS X
os.version: 26.2
os.arch: aarch64

I created the simplest build.mill file I could think of (uncached to always see the print output)

package build
import mill.*

object foo extends Module {
  def bar = Task.Uncached { println("hello world") }
}

I then run ./mill foo.bar with this output:

$ ./mill foo.bar
build.mill-68] compile compiling 3 Scala sources to out/mill-build/compile.dest/classes ...
build.mill-68] done compiling
1] foo.bar hello world
1/1, SUCCESS] ./mill foo.bar 4s

What are the tags at the beginning of the lines? I cannot seem to find them in any documentation.
They also feel incomplete, are they some artifacts from incorrect output processing?

Is my terminal setup / shell config causing these?
I tried either wezterm (TERM=wezterm) or iterm2 (TERM=xterm-256color), zsh or bash with or without any rc files, same output is present.

[lihaoyi]

The prefixes are indicators of what task each log line belongs to. In a trivial task like version they are perhaps not useful, but for any larger build they help demarcate where the output for each task starts and ends, even when multiple tasks may be running in parallel. Try building some actual code and it should become clear