printlns interfere with show during first time setup

[ghostbuster91]

Hi,

When calling ./mill show version for the very first time on a new machine mill will print on stdout:

Preparing Java 17.0.8.1 runtime; this may take a minute or two ...
"0.1.1"

Expected behavior

Stdout should only contain the result of the show command nothing besides that.

Actual behavior

Stdout contains information about preparing java together with results of the show command.

Reproduction steps

Use following docker file:

FROM ubuntu:22.04

# Install OpenJDK-8
RUN apt-get update && \
    apt-get install -y openjdk-17-jdk curl jq && \
    apt-get clean;

COPY . /src/
WORKDIR /src
RUN ./mill show version > output
RUN cat output

mill-version: 0.11.4

The offending line is here

mill/runner/src/mill/runner/MillMain.scala

Line 193 in 7c2114e

s"Preparing Java ${System.getProperty("java.version")} runtime; this may take a minute or two ..."

Somehow related to #2680

[lefou]

Looks reasonable. Instead, we should use the logger in scope, as it's using output streams that get properly redirected by show.

[kubukoz]

@lefou any idea why it wasn't ultimately solved by #2689 ?

[lihaoyi]

The setting up of the Java runtime happens pretty early; it might possibly happen before we set up the stream redirection

[lefou]

@lefou any idea why it wasn't ultimately solved by #2689 ?

No, not really. The code location you linked is already inside a SystemStreams.withStreams block, so any configured redirections to System.{in,out,err} and Console.{in,out,err} should be in place. Some debugging might be necessary to better understand what's going on.