Changing the build requires deleting `out` dir

[Arthurm1]

If I have a build starting with...

extends: millbuild.ProjectBaseModule

Compile it successfully and then change it to...

extends:
- ScalaModule
- SbtModule
scalaVersion: 3.8.0

Compile it again and I get the error...

scalaVersion: 3.8.0
^
key "scalaVersion" does not override any task on ScalaModule, SbtModule

Deleting the out dir and recompiling fixes the issue.

[lihaoyi]

@Arthurm1 can you upload a .zip file containing the project along with a console trace of a reproduction? At least my cursory attempt at following your instructions did not reproduce the issue

[Arthurm1]

I'll see if I can create a minimal project

[Arthurm1]

mill.zip

unzip project

run cd mill
run mill __.compile
All fine.

change projects/bar/package.mill.yaml from...

extends: millbuild.ProjectBaseModule
moduleDeps:
- projects.foo

to...

extends:
- ScalaModule
- SbtModule
scalaVersion: 3.8.0
moduleDeps:
- projects.foo

run mill __.compile again

get error.

I'm on Windows.

[lihaoyi]

Managed to reproduce it, thanks @Arthurm1! This will be super helpful in fixing the issue

[lihaoyi]

Should be the same root cause as #6764 probably

[lihaoyi]

Minimal Repro

build.mill.yaml

#empty

foo/package.mill.yaml

#empty

foo/bar/package.mill.yaml

extends: JavaModule
#extends: ScalaModule
#scalaVersion: 3.8.0

Running __.compile, converting the JavaModule to a ScalaModule, then __.compile again triggers the misbehavior

For this repro at least, the nested foo layer between bar and the project root seems necessary to make the problem happen