Add a `dotty-interfaces` package

We introduce a new entry point for the compiler in
`dotty.tools.dotc.Driver`:
```
def process(args: Array[String], simple: interfaces.SimpleReporter,
  callback: interfaces.CompilerCallback): interfaces.ReporterResult
```
Except for `args` which is just an array, the argument types and return
type of this method are Java interfaces defined in a new package called
`dotty-interfaces` which has a stable ABI. This means that you can
programmatically run a compiler with a custom reporter and callbacks
without having to recompile it against every version of dotty: you only
need to have `dotty-interfaces` present at compile-time and call the
`process` method using Java reflection.

See `test/test/InterfaceEntryPointTest.scala` for a concrete example.

This design is based on discussions with the IntelliJ IDEA Scala plugin
team. Thanks to Nikolay Tropin for the discussions and his PR
proposal (see #1011).

1 files changed, 10 insertions, 1 deletions

diff --git a/project/Build.scala b/project/Build.scala
index 980c7ccb0..8b7238a09 100644
--- a/project/Build.scala
+++ b/project/Build.scala
@@ -35,7 +35,16 @@ object DottyBuild extends Build {
     )
   }
 
+  lazy val `dotty-interfaces` = project.in(file("interfaces")).
+    settings(
+      // Do not append Scala versions to the generated artifacts
+      crossPaths := false,
+      // Do not depend on the Scala library
+      autoScalaLibrary := false
+    )
+
   lazy val dotty = project.in(file(".")).
+    dependsOn(`dotty-interfaces`).
     settings(
       // set sources to src/, tests to test/ and resources to resources/
       scalaSource in Compile := baseDirectory.value / "src",
@@ -105,7 +114,7 @@ object DottyBuild extends Build {
       parallelExecution in Test := false,
 
       // http://grokbase.com/t/gg/simple-build-tool/135ke5y90p/sbt-setting-jvm-boot-paramaters-for-scala
-      javaOptions <++= (managedClasspath in Runtime, packageBin in Compile) map { (attList, bin) =>
+      javaOptions <++= (dependencyClasspath in Runtime, packageBin in Compile) map { (attList, bin) =>
         // put the Scala {library, reflect} in the classpath
         val path = for {
           file <- attList.map(_.data)