Add JavaModule.mandatoryJavacOptions

[lefou]

This will hold options contributed by traits like ErrorProneModule.

Those are not propagated to the inner test traits intentionally, since those options are typically configured by other means, e.g. dedicated targets.

I also removed propagation of ScalaModule.mandatoryScalacOptions to its inner ScalaTests trait, for that same reasons and for consistence. Now all mandatory* targets don't propagate their values to inner tests.

[lihaoyi]

I think the idea sounds reasonable. Why is it called managed instead of mandatory? Should we standardize on one name?

In the past the convention was just that mandatory* were things that traits would set and end users wouldn't. Are we adding a new convention that they're also not propagated? That seems fine, but is something to be aware of (and probably should be written down somewhere)

[lefou]

I though about mandatory, but went with a different name as the main goal was to have a different propagation behavior then the preexisting mandatoryIvyDeps and mandatoryScalacOptions.

Both could be changed to no propagate (their value should still compute to the same value, which is a good indicator) too, but unfortunately, this would be a binary incompatible change and has to wait for Mill 0.13.

For the sake of consistency, I can change to mandatoryJavacOptions, although the name is even less descriptive.

[lefou]

Changed to mandatoryJavacOptions.

[lihaoyi]

yeah the name could be improved, maybe in 0.13.0 or something. Until then we'll just have to compensate by writing really good scaladoc so people who encounter it can read what it is for

[lolgab]

What if we exposed a task in JavaModule that decides how dependencies are propagated to the Tests submodules?
It could be something like:

def javacOptionsTestsPropagation: Task[Seq[String] => Seq[String]] = T.task { identity }

This way your plugin can override it to filter out the option that you don't want to propagate.

[lefou]

I think filtering options isn't my favorite go-to solution, since it's always a bit error-prone. Since we use stackable traits which can't be removed we also should take care to not add unnecessary options, which can't be easily removed. The new mandaroryJavacOptions already addresses this.

[lefou]

I took the opportunity to no longer propagate mandatoryScalacOptions to tests, to see if all tests pass. They should. I kept the override to just call super, so that binaries expecting this def in ScalaTests should work without issues.

[lefou]

I checked, we're not propagating mandatoryIvyDeps to tests, so we now no longer propagate any mandatory* target to tests. Nice and consistent.

[lihaoyi]

Not propagating mandatoryScalacOptions sounds fine. If the test module needs it they can inherit the trait (and often already do in cases like ScalaJs options or ScalaNative options)