SBT Plugin Support

[davidhoyt]

I recognize the perhaps conflict of interest in this request but for me to migrate to Bazel, I'd need to be able to continue to build and release SBT plugins that other teams still rely on. Is this a possibility?

I'm still very new to Bazel so my ability to contribute is very limited.

Thanks for taking the time to consider this!

[srdo]

It's almost certainly possible, but probably a bit of effort. You'll be trying to create a jar that "looks like" an sbt plugin jar, but since you don't have sbt to handle the scaffolding for you, you'll need to do this by hand.

I think an sbt plugin is mostly just a regular Scala library that depends on sbt, as you can see here https://repo1.maven.org/maven2/com/eed3si9n/sbt-assembly_2.8.1/sbt0.10.1_0.6/sbt-assembly_2.8.1-sbt0.10.1_0.6.pom, plus a metadata file as you can see if you open https://repo1.maven.org/maven2/com/eed3si9n/sbt-assembly_2.8.1/sbt0.10.1_0.6/sbt-assembly_2.8.1-sbt0.10.1_0.6.jar

Probably the way to get started is that you take one of your plugins and look at the jar sbt produces, then try to set up Bazel to create a similar jar, using scala_library and maybe a genrule to manually add in extra files if you need to.

Edit: Though before you invest time, consider if you can't migrate your build to Bazel and just cut out your plugins into separate sbt projects. That could easily be less effort.

[davidhoyt]

In my situation, other teams depend on what we produce and their migration would have to be piecemeal over time.

SBT plugins have specific artifact names and maven/publishing layouts as well which is why I felt a rule around this would be best. Plus we'd have to consider cross-compiling (targeting multiple SBT versions).