Separate documentation module

[charpov]

I'm experimenting with moving some of my sbt setup to mill. I'm also trying to push the yaml syntax as far as it'll go before I switch to Scala definitions.
With sbt, I was able to separate my configuration into multiple files, say build.sbt and doc.sbt, all applying to the same project. It seems that each Mill yaml file defines a new module, which is not what I want. Instead, I tried to create a separate module for documentation:

.
├── build.mill.yaml
├── mill
├── doc
│   └── package.mill.yaml
└── src
    └── dummy
        └── add.scala

My problem is to inherit from the default, unnamed module. I've tried something like this in a doc/package.mill.yaml file:

extends: build
scalaDocOptions:
  - -project:dummy

This doesn't work. I don't know what to extend to access the default, unnamed module.

[charpov]

I've made enough progress to know I'll switch from sbt to Mill for my teaching projects. The overall configuration is much simpler.

Still, I've lost some modularity that I'd like to bring back, if possible. My current Mill config is something like:

extends: ScalaModule
scalaVersion: 3.8.3
artifactName: &name dummy

mvnDeps: [io.github.charpov::tiny-scala-utils:1.8.0]
sources: !append [src-instructor/]
scalacOptions:
  - -deprecation    # Emit warning and location for usages of deprecated APIs.
  - -encoding:utf-8 # Specify character encoding used by source files.
  - -feature        # Emit warning for usages of features that should be imported explicitly.
  - -unchecked      # Enable detailed unchecked (erasure) warnings.
  - -Wunused:linted # Check unused imports and variables.
  - -preview        # Enable the use of preview features anywhere in the project.
  - -Yimports:java.lang,scala,scala.Predef,tinyscalautils.assertions # Tiny assertions
  - -source:future

scalaDocOptions:
  - -project
  - *name
  - "-project-footer:CS761/861: Programming Language Concepts and Features"
  - -groups
  - -external-mappings:.*scala/.*::scaladoc3::https://scala-lang.org/api/3.x/

With sbt, I was able split this into a student file (without the ScalaDoc configuration and the -source:future option) and additional files for myself to set additional options and the name of each project (here dummy). Is there any way to write this as two (or more) yaml files?

[lihaoyi]

we dont support yaml file inheritance. What you can do is write a scala trait in mill-build/src and use it in the yaml file extends clause. Slightly more complex than yaml but maybe sufficient?

You can also publish your trait to maven central as a plugin and the depend on it via mill-build: mvnDeps: to use it in extends, which would remove the latency of compiling scala every time someone checks out the repo

[charpov]

Good to know about mill-build/src, but I don't think it'll help me achieve what I want, which is to modify the configuration by adding or removing a file. It's not a big deal. The files and small and I can keep two separate version. The whole setup is still simpler than what I had with sbt.