Fix runBefore with :=

sbt/src/sbt-test/actions/task-map/build.sbt

@@ -3,11 +3,21 @@ val taskB = taskKey[File]("")
 val taskC = taskKey[File]("")
 val taskD = taskKey[File]("")
 
+val taskE = taskKey[File]("")
+val taskF = taskKey[File]("")
+val taskG = taskKey[File]("")
+val taskH = taskKey[File]("")
+
 taskA := touch(target.value / "a")
 taskB := touch(target.value / "b")
 taskC := touch(target.value / "c")
 taskD := touch(target.value / "d")
 
+taskE := touch(target.value / "e")
+taskF := touch(target.value / "f")
+taskG := touch(target.value / "g")
+taskH := touch(target.value / "h")
+
 //   a <<= a triggeredBy b
 // means "a" will be triggered by "b"
 // said differently, invoking "b" will run "b" and then run "a"
@@ -15,6 +25,13 @@ taskD := touch(target.value / "d")
 taskA <<= taskA triggeredBy taskB
 taskC := (taskC triggeredBy taskD).value
 
+//   e <<= e runBefore f
+// means "e" will be run before running "f"
+// said differently, invoking "f" will run "e" and then run "f"
+
+taskE <<= taskE runBefore taskF
+taskG := (taskG runBefore taskH).value
+
 
 
 // test utils

sbt/src/sbt-test/actions/task-map/test

@@ -0,0 +1,15 @@
+> taskB
+$ exists target/b
+$ exists target/a
+
+> taskD
+$ exists target/d
+$ exists target/c
+
+> taskF
+$ exists target/e
+$ exists target/f
+
+> taskH
+$ exists target/g
+$ exists target/h

sbt/src/sbt-test/actions/triggeredby/test

@@ -1,7 +0,0 @@
-> taskB
-$ exists target/b
-$ exists target/a
-
-> taskD
-$ exists target/d
-$ exists target/c

tasks/standard/src/main/scala/sbt/std/TaskExtra.scala

@@ -118,10 +118,11 @@ trait TaskExtra {
     def result: Task[Result[S]] = mapR(idFun)
 
     private val triggeredByKey = AttributeKey[Seq[Task[_]]]("triggered-by")
-    private def newInfo[A]: Info[A] = {
-      val i = Info[A]()
-      (in.info get triggeredByKey).fold(i)(i.set(triggeredByKey, _))
-    }
+    private val runBeforeKey = AttributeKey[Seq[Task[_]]]("run-before")
+    private def newInfo[A]: Info[A] =
+      Seq(triggeredByKey, runBeforeKey)
+        .flatMap(k => (in.info get k) map (k -> _))
+        .foldLeft(Info[A]()) { case (i, (k, v)) => i.set(k, v) }
 
     def flatMapR[T](f: Result[S] => Task[T]): Task[T] = Task(Info(), new FlatMapped[T, K](in, f, ml))
     def mapR[T](f: Result[S] => T): Task[T] = Task(newInfo, new Mapped[T, K](in, f, ml))