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, 16 insertions, 4 deletions

diff --git a/src/dotty/tools/backend/jvm/GenBCode.scala b/src/dotty/tools/backend/jvm/GenBCode.scala
index 2d444d3be..8cec93977 100644
--- a/src/dotty/tools/backend/jvm/GenBCode.scala
+++ b/src/dotty/tools/backend/jvm/GenBCode.scala
@@ -13,6 +13,9 @@ import dotty.tools.dotc
 import dotty.tools.dotc.backend.jvm.DottyPrimitives
 import dotty.tools.dotc.transform.Erasure
 
+import dotty.tools.dotc.interfaces
+import java.util.Optional
+
 import scala.reflect.ClassTag
 import dotty.tools.dotc.core._
 import Periods._
@@ -51,7 +54,17 @@ class GenBCodePipeline(val entryPoints: List[Symbol], val int: DottyBackendInter
 
   var tree: Tree = _
 
-  val sourceJFile: JFile = ctx.compilationUnit.source.file.file
+  val sourceFile = ctx.compilationUnit.source
+
+  /** Convert a `scala.reflect.io.AbstractFile` into a
+   *  `dotty.tools.dotc.interfaces.AbstractFile`.
+   */
+  private[this] def convertAbstractFile(absfile: scala.reflect.io.AbstractFile): interfaces.AbstractFile =
+    new interfaces.AbstractFile {
+      override def name = absfile.name
+      override def path = absfile.path
+      override def jfile = Optional.ofNullable(absfile.file)
+    }
 
   final class PlainClassBuilder(cunit: CompilationUnit) extends SyncAndTryBuilder(cunit)
 
@@ -307,7 +320,7 @@ class GenBCodePipeline(val entryPoints: List[Symbol], val int: DottyBackendInter
       // Statistics.stopTimer(BackendStats.bcodeTimer, bcodeStart)
 
       if (ctx.compilerCallback != null)
-        ctx.compilerCallback.onSourceCompiled(sourceJFile)
+        ctx.compilerCallback.onSourceCompiled(sourceFile)
 
       /* TODO Bytecode can be verified (now that all classfiles have been written to disk)
        *
@@ -373,10 +386,9 @@ class GenBCodePipeline(val entryPoints: List[Symbol], val int: DottyBackendInter
               else getFileForClassfile(outFolder, jclassName, ".class")
             bytecodeWriter.writeClass(jclassName, jclassName, jclassBytes, outFile)
 
-            val outJFile = outFile.file
             val className = jclassName.replace('/', '.')
             if (ctx.compilerCallback != null)
-              ctx.compilerCallback.onClassGenerated(sourceJFile, outJFile, className)
+              ctx.compilerCallback.onClassGenerated(sourceFile, convertAbstractFile(outFile), className)
           }
           catch {
             case e: FileConflictException =>