--meta-level 1 show sources triggers compilation

[lefou]

In an existing project with a meta-build, running mill --meta-level 1 show sources triggers compilation in the same meta-level. This comes to a surprise, as compilation depends on the sources and I was in the process to analyze a compile error, for which I wanted to inspect the sources.

Reproducer:

// build.sc
import $meta._

this is a build error

// mill-build/build.sc
object `package` extends MillBuildRootModule

> mill --meta-level 1 show "{sources,allSourceFiles}"
No mill version specified.
You should provide a version via '.mill-version' file or --mill-version option.
Using mill version 0.12.0
[mill-build/build.mill-57/61] compile
[mill-build/build.mill-57] [info] compiling 1 Scala source to /tmp/mill2/out/mill-build/mill-build/compile.dest/classes ...
[mill-build/build.mill-57] [info] done compiling
[build.mill-57/61] compile
[build.mill-57] [info] compiling 1 Scala source to /tmp/mill2/out/mill-build/compile.dest/classes ...
[build.mill-57] [error] /tmp/mill2/build.mill:6:6: value is is not a member of build_.package_
[build.mill-57] [error] this is a build error
[build.mill-57] [error]      ^
[build.mill-57] [error] /tmp/mill2/build.mill:6:9: not found: value a
[build.mill-57] [error] this is a build error
[build.mill-57] [error]         ^
[build.mill-57] [error] /tmp/mill2/build.mill:6:17: not found: value error
[build.mill-57] [error] this is a build error
[build.mill-57] [error]                 ^
[build.mill-57] [error] three errors found
[61/61] ====================================================================================================== show {sources,allSourceFiles} ==========================================================================================================
1 tasks failed
compile Compilation failed

I would expect to see just the sources files, so I can examine them to probably spot any issues resulting in the compile error.

[lefou]

Seem this isn't a newly introduced issue. I can reproduce this with Mill 0.11.0 too.

> MILL_VERSION="0.11.0" mill --meta-level 1 show sources
[mill-build/build.sc] [41/49] compile 
[info] compiling 1 Scala source to /tmp/mill2/out/mill-build/mill-build/compile.dest/classes ...
[info] done compiling
[build.sc] [41/49] compile 
[info] compiling 1 Scala source to /tmp/mill2/out/mill-build/compile.dest/classes ...
[error] /tmp/mill2/build.sc:3:6: value is is not a member of millbuild.build
[error] this is a build error
[error]      ^
[error] /tmp/mill2/build.sc:3:9: not found: value a
[error] this is a build error
[error]         ^
[error] /tmp/mill2/build.sc:3:17: not found: value error
[error] this is a build error
[error]                 ^
[error] three errors found
1 targets failed
compile Compilation failed