Emacs ENSIME - incremental compile

Question

I'm pretty new to ENSIME. I'm trying to do incremantal compilation within Emacs by compiling single file one-by-one with SBT . Let's say I have a file a.scala that imports a class in file b.scala. If I try to compile only a.scala using C-c C-b C it obviously complains as b.scala has not been compiled. If I try to compile b.scala still using C-c C-b C it correctly compiles, but after that I still cannot compile a.scala.

I tried using the same procedure of compiling b.scala and a.scala using IntelliJ and it works fine. What am I missing?

Answer 1

Glancing at the code for ensime-sbt, it doesn't look like the target class-path is included in the input class-path. As such, while ensimeCompileOnly sees the JAR dependencies, it would not see any peer compiled classes (I am observing this with sbt 1.x.x). Ideally, it would and I don't think there is a strong reason to do otherwise.

Have a look at CompatExtras.scala where the compileOnlyTask is defined. Also, perhaps open up a ticket on ensime-sbt, and try to open a discussion. If what is implemented is ideal, then the documentation could be updated to reflect that.

Just to note, Ensime does not have a dedicated maintainer today. A few of us lurk to help contributions get merged in occasionally. The highest chance of this being fixed is by being proactive. I'd start by updating the tests found in ./src/sbt-test-0.13/sbt-ensime/compile-only/test to have project dependencies (you'll notice that there are none between Foo, Baz, and FooTest). Perhaps you could have FooTest reference Foo, and watch the test fail, and proceed accordingly.