Move `ScalaWorkerApi`/`ScalaJSBridge` over to new `ExternalModule` class

Also add a simple unit to validate that you can use `ExternalModule`s as part of a build, and that the

4 files changed, 67 insertions, 7 deletions

diff --git a/core/src/mill/define/Module.scala b/core/src/mill/define/Module.scala
index 09e8e974..11a98d95 100644
--- a/core/src/mill/define/Module.scala
+++ b/core/src/mill/define/Module.scala
@@ -95,10 +95,9 @@ object BaseModule{
 class BaseModule(basePath0: Path)
                 (implicit millModuleEnclosing0: sourcecode.Enclosing,
                  millModuleLine0: sourcecode.Line,
-                 millName0: sourcecode.Name,
-                 overrides0: Overrides)
+                 millName0: sourcecode.Name)
   extends Module()(
-    mill.define.Ctx.make(implicitly, implicitly, implicitly, BasePath(basePath0), Segments(), implicitly)
+    mill.define.Ctx.make(implicitly, implicitly, implicitly, BasePath(basePath0), Segments(), Overrides(0))
   ){
   // A BaseModule should provide an empty Segments list to it's children, since
   // it is the root of the module tree, and thus must not include it's own
@@ -107,4 +106,16 @@ class BaseModule(basePath0: Path)
   override def basePath = millOuterCtx.basePath
   override implicit def millModuleBasePath: BasePath = BasePath(basePath)
   implicit def millImplicitBaseModule: BaseModule.Implicit = BaseModule.Implicit(this)
+}
+
+class ExternalModule(implicit millModuleEnclosing0: sourcecode.Enclosing,
+                     millModuleLine0: sourcecode.Line,
+                     millName0: sourcecode.Name) extends BaseModule(ammonite.ops.pwd){
+  assert(
+    !" #".exists(millModuleEnclosing0.value.contains(_)),
+    "External modules must be at a top-level static path, not " + millModuleEnclosing0.value
+  )
+  override implicit def millModuleSegments = {
+    Segments(millModuleEnclosing0.value.split('.').map(Segment.Label):_*)
+  }
 }
\ No newline at end of file
diff --git a/core/test/src/mill/eval/ModuleTests.scala b/core/test/src/mill/eval/ModuleTests.scala
new file mode 100644
index 00000000..110e8c79
--- /dev/null
+++ b/core/test/src/mill/eval/ModuleTests.scala
@@ -0,0 +1,47 @@
+package mill.eval
+
+import ammonite.ops._
+import mill.util.{TestEvaluator, TestUtil}
+import mill.T
+import mill.util.TestEvaluator.implicitDisover
+import utest._
+
+
+object ModuleTests extends TestSuite{
+  object ExternalModule extends mill.define.ExternalModule {
+    def x = T{13}
+    object inner extends mill.Module{
+      def y = T{17}
+    }
+  }
+  object Build extends TestUtil.BaseModule{
+    def z = T{ ExternalModule.x() + ExternalModule.inner.y() }
+  }
+  val tests = Tests {
+    'externalModuleTargetsAreNamespacedByModulePackagePath - {
+      val check = new TestEvaluator(
+        Build,
+        pwd / 'target / 'workspace / "module-tests" / "externalModule",
+        pwd
+      )
+
+      val Right((30, 1)) = check.apply(Build.z)
+      val base = check.evaluator.workspacePath
+      assert(
+        read(base / 'z / "meta.json").contains("30"),
+        read(base / 'mill / 'eval / 'ModuleTests / 'ExternalModule / 'x / "meta.json").contains("13"),
+        read(base / 'mill / 'eval / 'ModuleTests / 'ExternalModule / 'inner / 'y / "meta.json").contains("17")
+      )
+    }
+    'externalModuleMustBeGlobalStatic - {
+
+
+      object Build extends mill.define.ExternalModule {
+
+        def z = T{ ExternalModule.x() + ExternalModule.inner.y() }
+      }
+
+      intercept[java.lang.AssertionError]{ Build }
+    }
+  }
+}
diff --git a/core/test/src/mill/util/TestEvaluator.scala b/core/test/src/mill/util/TestEvaluator.scala
index 2301efe6..41830d48 100644
--- a/core/test/src/mill/util/TestEvaluator.scala
+++ b/core/test/src/mill/util/TestEvaluator.scala
@@ -9,10 +9,10 @@ import language.experimental.macros
 object TestEvaluator{
   implicit def implicitDisover[T]: Discover[T] = macro applyImpl[T]
 }
-class TestEvaluator[T <: TestUtil.BaseModule](module: T,
-                                              workspacePath: Path,
-                                              basePath: Path)
-                                             (implicit discover: Discover[T]){
+class TestEvaluator[T <: TestUtil.TestBuild](module: T,
+                                             workspacePath: Path,
+                                             basePath: Path)
+                                            (implicit discover: Discover[T]){
   val evaluator = new Evaluator(workspacePath, basePath, module, discover, DummyLogger)
 //  val evaluator = new Evaluator(workspacePath, basePath, module, discover, new PrintLogger(true, ammonite.util.Colors.Default, System.out, System.out, System.err))
   def apply[T](t: Task[T]): Either[Result.Failing, (T, Int)] = {
diff --git a/core/test/src/mill/util/TestUtil.scala b/core/test/src/mill/util/TestUtil.scala
index 1af12a74..3a025a91 100644
--- a/core/test/src/mill/util/TestUtil.scala
+++ b/core/test/src/mill/util/TestUtil.scala
@@ -8,11 +8,13 @@ import mill.util.Strict.Agg
 import scala.collection.mutable
 
 object TestUtil {
+  trait TestBuild extends mill.define.Module
   class BaseModule(implicit millModuleEnclosing0: sourcecode.Enclosing,
                    millModuleLine0: sourcecode.Line,
                    millName0: sourcecode.Name,
                    overrides: Overrides)
     extends mill.define.BaseModule(ammonite.ops.pwd / millModuleEnclosing0.value)
+  with TestBuild
 
   object test{