Make builds able to depend on external projects (#291)

* Make builds able to depend on external projects

Builds are now able to load external projects and depend on them
as if they were local submodules.

`import $file.external.path.build`

* Disambiguate "dest" for foreign modules.

* Calling modules loaded from external directories "Foreign" to avoid
conflicting with the already existing concept of "ExternalModule".
* Amended the way `dest` is computed for foreign modules
* Added tests to check that the source paths and dest are as expected
* Added a test to show that local modules do not conflict with foreign
modules when they are named the same

* WIP windows build fail

* Added bootstrapping step in CYGWIN CI job

* * Revert externalOutPath deletion
* Add documentation for foreign-modules

* reverting appveyor changes

* Disabling Foreign modules tests against Java9

See https://github.com/lihaoyi/mill/issues/302

1 files changed, 11 insertions, 4 deletions

diff --git a/main/src/mill/main/MainRunner.scala b/main/src/mill/main/MainRunner.scala
index fed664fd..a289db5f 100644
--- a/main/src/mill/main/MainRunner.scala
+++ b/main/src/mill/main/MainRunner.scala
@@ -1,9 +1,10 @@
 package mill.main
-import java.io.{InputStream, OutputStream, PrintStream}
+import java.io.{InputStream, PrintStream}
 
 import ammonite.Main
 import ammonite.interp.{Interpreter, Preprocessor}
 import ammonite.ops.Path
+import ammonite.util.Util.CodeSource
 import ammonite.util._
 import mill.eval.{Evaluator, PathRef}
 import mill.util.PrintLogger
@@ -120,20 +121,26 @@ class MainRunner(val config: ammonite.main.Cli.Config,
 
   object CustomCodeWrapper extends Preprocessor.CodeWrapper {
     def apply(code: String,
-              pkgName: Seq[ammonite.util.Name],
+              source: CodeSource,
               imports: ammonite.util.Imports,
               printCode: String,
               indexedWrapperName: ammonite.util.Name,
               extraCode: String): (String, String, Int) = {
+      import source.pkgName
       val wrapName = indexedWrapperName.backticked
-      val literalPath = pprint.Util.literalize(config.wd.toString)
+      val path = source
+        .path
+        .map(path => path.toNIO.getParent)
+        .getOrElse(config.wd.toNIO)
+      val literalPath = pprint.Util.literalize(path.toString)
+      val external = !(path.compareTo(config.wd.toNIO) == 0)
       val top = s"""
         |package ${pkgName.head.encoded}
         |package ${Util.encodeScalaSourcePath(pkgName.tail)}
         |$imports
         |import mill._
         |object $wrapName
-        |extends mill.define.BaseModule(ammonite.ops.Path($literalPath))
+        |extends mill.define.BaseModule(ammonite.ops.Path($literalPath), foreign0 = $external)
         |with $wrapName{
         |  // Stub to make sure Ammonite has something to call after it evaluates a script,
         |  // even if it does nothing...