Allow Target creation from Result[T] (#79)

2 files changed, 17 insertions, 1 deletions

diff --git a/core/src/main/scala/mill/define/Task.scala b/core/src/main/scala/mill/define/Task.scala
index 17392725..71a98fa7 100644
--- a/core/src/main/scala/mill/define/Task.scala
+++ b/core/src/main/scala/mill/define/Task.scala
@@ -40,7 +40,7 @@ object Target extends Applicative.Applyer[Task, Task, Result, Ctx]{
 
   implicit def apply[T](t: T): Target[T] = macro targetImpl[T]
 
-  implicit def apply[T](t: Result[T]): Target[T] = macro targetImpl[T]
+  implicit def apply[T](t: Result[T]): Target[T] = macro targetResultImpl[T]
 
   def apply[T](t: Task[T]): Target[T] = macro targetTaskImpl[T]
 
@@ -88,6 +88,15 @@ object Target extends Applicative.Applyer[Task, Task, Result, Ctx]{
     )
   }
 
+  def targetResultImpl[T: c.WeakTypeTag](c: Context)(t: c.Expr[Result[T]]): c.Expr[Target[T]] = {
+    import c.universe._
+    c.Expr[Target[T]](
+      mill.plugin.Cacher.wrapCached(c)(
+        q"new ${weakTypeOf[TargetImpl[T]]}(${Applicative.impl0[Task, T, Ctx](c)(t.tree).tree}, _root_.sourcecode.Enclosing())"
+      )
+    )
+  }
+
   def underlying[A](v: Task[A]) = v
   def mapCtx[A, B](t: Task[A])(f: (A, Ctx) => Result[B]) = t.mapDest(f)
   def zip() =  new Task.Task0(())
diff --git a/core/src/test/scala/mill/define/CacherTests.scala b/core/src/test/scala/mill/define/CacherTests.scala
index 4e647f82..fe8e1b89 100644
--- a/core/src/test/scala/mill/define/CacherTests.scala
+++ b/core/src/test/scala/mill/define/CacherTests.scala
@@ -4,6 +4,7 @@ import mill.discover.Discovered
 import mill.eval.Evaluator
 import mill.util.{DummyLogger, OSet}
 import mill.T
+import mill.eval.Result.Success
 import utest._
 import utest.framework.TestPath
 
@@ -11,6 +12,7 @@ object CacherTests extends TestSuite{
   object Base extends Base
   trait Base extends Task.Module{
     def value = T{ 1 }
+    def result = T{ Success(1) }
   }
   object Middle extends Middle
   trait Middle extends Base{
@@ -36,6 +38,11 @@ object CacherTests extends TestSuite{
       eval(Discovered.mapping(Base), Base.value) == 1
     )
 
+    'resultDefIsCached - assert(
+      Base.result eq Base.result,
+      eval(Discovered.mapping(Base), Base.result) == 1
+    )
+
     val middleMapping = Discovered.mapping(Middle)
 
     'overridingDefIsAlsoCached - assert(