First pass at splitting out worker-api from mill core. (#504)

This reduces the {scala,scalajs,scalanative}-worker dependency from the entirety of Mill to a much narrower `mill.api` module. This reduces the amount of classpath pollution within these workers, should mean they're much faster to download the first time, and reduces the amount of random junk they would pull in if they were to be used outside of the Mill project.

The interactions between the various *Modules and their *WorkerImpls has been narrowed down to the `*.api` modules, which only depend on other `*.api` modules.

A lot of things have been moved around; user code is unlikely to break, but it's possible some will if it references classes that have been moved around. Forwarders have been left for the few internal classes that Mill uses in it's own `build.sc`, to support bootstrapping. Third-party code which breaks should be a straightforward to fix just by updating imports

The `*.api` modules have minimal dependencies (mostly uPickle and os-lib) and minimal code. There is still a bunch of implementation code in there: some of it defining data-types that are commonly sent across the module/worker interface (`Agg`, `PathRef`, ...), and some of it just general helper functions that are needed both in modules and workers. The latter code isn't strictly API definitions, but for now is small enough it's not worth splitting into it's own module

5 files changed, 66 insertions, 61 deletions

diff --git a/scalanativelib/api/src/mill/scalanativelib/api/ScalaNativeWorkerApi.scala b/scalanativelib/api/src/mill/scalanativelib/api/ScalaNativeWorkerApi.scala
new file mode 100644
index 00000000..e1fee0da
--- /dev/null
+++ b/scalanativelib/api/src/mill/scalanativelib/api/ScalaNativeWorkerApi.scala
@@ -0,0 +1,60 @@
+package mill.scalanativelib.api
+
+import upickle.default.{macroRW, ReadWriter => RW}
+import java.io.File
+import sbt.testing.Framework
+
+trait ScalaNativeWorkerApi {
+  def discoverClang: os.Path
+  def discoverClangPP: os.Path
+  def discoverTarget(clang: os.Path, workDir: os.Path): String
+  def discoverCompileOptions: Seq[String]
+  def discoverLinkingOptions: Seq[String]
+
+  def config(nativeLibJar: os.Path,
+             mainClass: String,
+             classpath: Seq[os.Path],
+             nativeWorkdir: os.Path,
+             nativeClang: os.Path,
+             nativeClangPP: os.Path,
+             nativeTarget: String,
+             nativeCompileOptions: Seq[String],
+             nativeLinkingOptions: Seq[String],
+             nativeGC: String,
+             nativeLinkStubs: Boolean,
+             releaseMode: ReleaseMode,
+             logLevel: NativeLogLevel): NativeConfig
+
+  def defaultGarbageCollector: String
+  def nativeLink(nativeConfig: NativeConfig, outPath: os.Path): os.Path
+
+  def newScalaNativeFrameWork(framework: Framework, id: Int, testBinary: File,
+                              logLevel: NativeLogLevel, envVars: Map[String, String]): Framework
+}
+
+
+sealed abstract class NativeLogLevel(val level: Int) extends Ordered[NativeLogLevel] {
+  def compare(that: NativeLogLevel) =  this.level - that.level
+}
+
+object NativeLogLevel {
+  case object Error extends NativeLogLevel(200)
+  case object Warn extends NativeLogLevel(300)
+  case object Info extends NativeLogLevel(400)
+  case object Debug extends NativeLogLevel(500)
+  case object Trace extends NativeLogLevel(600)
+
+  implicit def rw: RW[NativeLogLevel] = macroRW
+}
+
+sealed abstract class ReleaseMode(val name: String)
+
+object ReleaseMode {
+  case object Debug extends ReleaseMode("debug")
+  case object Release extends ReleaseMode("release")
+
+  implicit def rw: RW[ReleaseMode] = macroRW
+}
+
+// result wrapper to preserve some type safety
+case class NativeConfig(config: Any)
\ No newline at end of file
diff --git a/scalanativelib/src/mill/scalanativelib/ScalaNativeModule.scala b/scalanativelib/src/mill/scalanativelib/ScalaNativeModule.scala
index d8a282de..a7a2b96b 100644
--- a/scalanativelib/src/mill/scalanativelib/ScalaNativeModule.scala
+++ b/scalanativelib/src/mill/scalanativelib/ScalaNativeModule.scala
@@ -6,37 +6,14 @@ import java.net.URLClassLoader
 import coursier.Cache
 import coursier.maven.MavenRepository
 import mill.define.{Target, Task}
-import mill.eval.Result
+import mill.api.Result
 import mill.modules.Jvm
 import mill.scalalib.{Dep, DepSyntax, Lib, SbtModule, ScalaModule, TestModule, TestRunner}
 import mill.util.Loose.Agg
 import sbt.testing.{AnnotatedFingerprint, SubclassFingerprint}
 import sbt.testing.Fingerprint
 import upickle.default.{ReadWriter => RW, macroRW}
-
-
-sealed abstract class NativeLogLevel(val level: Int) extends Ordered[NativeLogLevel] {
-  def compare(that: NativeLogLevel) =  this.level - that.level
-}
-
-object NativeLogLevel {
-  case object Error extends NativeLogLevel(200)
-  case object Warn extends NativeLogLevel(300)
-  case object Info extends NativeLogLevel(400)
-  case object Debug extends NativeLogLevel(500)
-  case object Trace extends NativeLogLevel(600)
-
-  implicit def rw: RW[NativeLogLevel] = macroRW
-}
-
-sealed abstract class ReleaseMode(val name: String)
-
-object ReleaseMode {
-  case object Debug extends ReleaseMode("debug")
-  case object Release extends ReleaseMode("release")
-
-  implicit def rw: RW[ReleaseMode] = macroRW
-}
+import mill.scalanativelib.api._
 
 
 trait ScalaNativeModule extends ScalaModule { outer =>
diff --git a/scalanativelib/src/mill/scalanativelib/ScalaNativeWorkerApi.scala b/scalanativelib/src/mill/scalanativelib/ScalaNativeWorkerApi.scala
index be834e89..80325f1e 100644
--- a/scalanativelib/src/mill/scalanativelib/ScalaNativeWorkerApi.scala
+++ b/scalanativelib/src/mill/scalanativelib/ScalaNativeWorkerApi.scala
@@ -5,7 +5,7 @@ import java.net.URLClassLoader
 
 import mill.define.{Discover, Worker}
 import mill.{Agg, T}
-import sbt.testing.Framework
+import mill.scalanativelib.api._
 
 
 class ScalaNativeWorker {
@@ -38,38 +38,6 @@ class ScalaNativeWorker {
   }
 }
 
-
-// result wrapper to preserve some type safety
-case class NativeConfig(config: Any)
-
-trait ScalaNativeWorkerApi {
-  def discoverClang: os.Path
-  def discoverClangPP: os.Path
-  def discoverTarget(clang: os.Path, workDir: os.Path): String
-  def discoverCompileOptions: Seq[String]
-  def discoverLinkingOptions: Seq[String]
-
-  def config(nativeLibJar: os.Path,
-             mainClass: String,
-             classpath: Seq[os.Path],
-             nativeWorkdir: os.Path,
-             nativeClang: os.Path,
-             nativeClangPP: os.Path,
-             nativeTarget: String,
-             nativeCompileOptions: Seq[String],
-             nativeLinkingOptions: Seq[String],
-             nativeGC: String,
-             nativeLinkStubs: Boolean,
-             releaseMode: ReleaseMode,
-             logLevel: NativeLogLevel): NativeConfig
-
-  def defaultGarbageCollector: String
-  def nativeLink(nativeConfig: NativeConfig, outPath: os.Path): os.Path
-
-  def newScalaNativeFrameWork(framework: Framework, id: Int, testBinary: File,
-                              logLevel: NativeLogLevel, envVars: Map[String, String]): Framework
-}
-
 object ScalaNativeWorkerApi extends mill.define.ExternalModule {
   def scalaNativeWorker: Worker[ScalaNativeWorker] = T.worker { new ScalaNativeWorker() }
   lazy val millDiscover = Discover[this.type]
diff --git a/scalanativelib/test/src/mill/scalanativelib/HelloNativeWorldTests.scala b/scalanativelib/test/src/mill/scalanativelib/HelloNativeWorldTests.scala
index 37fbfc80..74d4238a 100644
--- a/scalanativelib/test/src/mill/scalanativelib/HelloNativeWorldTests.scala
+++ b/scalanativelib/test/src/mill/scalanativelib/HelloNativeWorldTests.scala
@@ -12,7 +12,7 @@ import utest._
 
 
 import scala.collection.JavaConverters._
-
+import mill.scalanativelib.api._
 
 object HelloNativeWorldTests extends TestSuite {
   val workspacePath =  TestUtil.getOutPathStatic() / "hello-native-world"
diff --git a/scalanativelib/worker/0.3/src/mill/scalanativelib/worker/ScalaNativeWorkerImpl.scala b/scalanativelib/worker/0.3/src/mill/scalanativelib/worker/ScalaNativeWorkerImpl.scala
index 8c24a39e..b32e84ff 100644
--- a/scalanativelib/worker/0.3/src/mill/scalanativelib/worker/ScalaNativeWorkerImpl.scala
+++ b/scalanativelib/worker/0.3/src/mill/scalanativelib/worker/ScalaNativeWorkerImpl.scala
@@ -4,13 +4,13 @@ import java.io.File
 import java.lang.System.{err, out}
 
 import scala.scalanative.build.{Build, Config, Discover, GC, Logger, Mode}
-import mill.scalanativelib.{NativeConfig, NativeLogLevel, ReleaseMode}
+import mill.scalanativelib.api.{NativeConfig, NativeLogLevel, ReleaseMode}
 import sbt.testing.Framework
 
 import scala.scalanative.testinterface.ScalaNativeFramework
 
 
-class ScalaNativeWorkerImpl extends mill.scalanativelib.ScalaNativeWorkerApi {
+class ScalaNativeWorkerImpl extends mill.scalanativelib.api.ScalaNativeWorkerApi {
   def logger(level: NativeLogLevel) =
     Logger(
       debugFn = msg => if (level >= NativeLogLevel.Debug) out.println(msg),