Fix incremental compilation when a Scala project depends on a Java project (#414)

* Upgrade ammonite to 1.1.2-30-53edc31

This is mainly to get https://github.com/lihaoyi/Ammonite/pull/851 which
should reduce the amount of unnecessary work done by incremental
compilation in the Mill build. This requires some code changes since
this means we now depend on a more recent version of coursier, as a
side-effect this means that we do not depend on scalaz anymore.

Also use the same ammonite version in the Mill build and in
ScalaModule#ammoniteReplClasspath.

Also remove an incorrect dependency in the caffeine integration test.
This was always wrong but did not start failing until this commit,
probably due to dependencies appearing in a different order on the
classpath.

* Rename ScalaWorker to ZincWorker

Starting with the next commit, it will be used in Java-only projects
too, so the name is misleading.

* Upgrade to Zinc 1.2.1

* Fix incremental compilation when a Scala project depends on a Java project

Before this commit, JavaModule#compile simply called javac
unconditionally, thus generating new classfiles every time. But if a
Scala project depends on a Java project, this will throw off the
incremental compilation algorithm which will unnecessarily recompile
files. To avoid this we now use Zinc to compile Java projects too (as a
bonus this means that Java compilation becomes incremental). This
required some refactoring in ZincWorkerImpl to be able to compile stuff
without having to pass Scala-specific options.

The issue solved by this commit could be reproduced by running in the
Mill repository:

$ mill main.compile
$ mill -i
@ main.compile()

and observing that before this commit, the `main.compile()` call ended
up recompiling code.

1 files changed, 14 insertions, 9 deletions

diff --git a/main/src/mill/modules/Jvm.scala b/main/src/mill/modules/Jvm.scala
index 3a6dcb9f..96992d20 100644
--- a/main/src/mill/modules/Jvm.scala
+++ b/main/src/mill/modules/Jvm.scala
@@ -10,6 +10,7 @@ import java.util.jar.{JarEntry, JarFile, JarOutputStream}
 
 import ammonite.ops._
 import coursier.{Cache, Dependency, Fetch, Repository, Resolution}
+import coursier.util.{Gather, Task}
 import geny.Generator
 import mill.main.client.InputPumper
 import mill.eval.{PathRef, Result}
@@ -383,7 +384,7 @@ object Jvm {
   /**
     * Resolve dependencies using Coursier.
     *
-    * We do not bother breaking this out into the separate ScalaWorker classpath,
+    * We do not bother breaking this out into the separate ZincWorkerApi classpath,
     * because Coursier is already bundled with mill/Ammonite to support the
     * `import $ivy` syntax.
     */
@@ -413,17 +414,19 @@ object Jvm {
 
       def load(artifacts: Seq[coursier.Artifact]) = {
         val logger = None
-        val loadedArtifacts = scalaz.concurrent.Task.gatherUnordered(
+
+        import scala.concurrent.ExecutionContext.Implicits.global
+        val loadedArtifacts = Gather[Task].gather(
           for (a <- artifacts)
-            yield coursier.Cache.file(a, logger = logger).run
+            yield coursier.Cache.file[Task](a, logger = logger).run
               .map(a.isOptional -> _)
-        ).unsafePerformSync
+        ).unsafeRun
 
         val errors = loadedArtifacts.collect {
-          case (false, scalaz.-\/(x)) => x
-          case (true, scalaz.-\/(x)) if !x.notFound => x
+          case (false, Left(x)) => x
+          case (true, Left(x)) if !x.notFound => x
         }
-        val successes = loadedArtifacts.collect { case (_, scalaz.\/-(x)) => x }
+        val successes = loadedArtifacts.collect { case (_, Right(x)) => x }
         (errors, successes)
       }
 
@@ -459,8 +462,10 @@ object Jvm {
       mapDependencies = mapDependencies
     )
 
-    val fetch = Fetch.from(repositories, Cache.fetch())
-    val resolution = start.process.run(fetch).unsafePerformSync
+    val fetch = Fetch.from(repositories, Cache.fetch[Task]())
+
+    import scala.concurrent.ExecutionContext.Implicits.global
+    val resolution = start.process.run(fetch).unsafeRun()
     (deps.toSeq, resolution)
   }
 }