Implement InternalActionResult

core-macros/src/main/scala/sbt/internal/util/appmacro/Cont.scala

@@ -356,16 +356,18 @@ trait Cont:
       // wrap body in between output var declarations and var references
       def letOutput[A1: Type](
           outputs: List[Output]
-      )(body: Expr[A1]): Expr[(A1, Seq[VirtualFile])] =
+      )(body: Expr[A1]): Expr[ActionCache.InternalActionResult[A1]] =
         Block(
           outputs.map(_.toVarDef),
           '{
-            (
+            ActionCache.InternalActionResult(
-              $body,
+              value = $body,
-              List(${ Varargs[VirtualFile](outputs.map(_.toRef.asExprOf[VirtualFile])) }: _*)
+              outputs = List(${
+                Varargs[VirtualFile](outputs.map(_.toRef.asExprOf[VirtualFile]))
+              }: _*),
             )
           }.asTerm
-        ).asExprOf[(A1, Seq[VirtualFile])]
+        ).asExprOf[ActionCache.InternalActionResult[A1]]
 
       val WrapOutputName = "wrapOutput_\u2603\u2603"
       // Called when transforming the tree to add an input.

util-cache/src/main/scala/sbt/util/ActionCache.scala

@@ -33,7 +33,7 @@ object ActionCache:
       extraHash: Digest,
       tags: List[CacheLevelTag],
   )(
-      action: I => (O, Seq[VirtualFile])
+      action: I => InternalActionResult[O],
   )(
       config: BuildWideCacheConfiguration
   ): O =
@@ -44,8 +44,8 @@ object ActionCache:
 
     def organicTask: O =
       // run action(...) and combine the newResult with outputs
-      val (result, outputs) =
+      val InternalActionResult(result, outputs) =
-        try action(key)
+        try action(key): @unchecked
         catch
           case e: Exception =>
             cacheEventLog.append(ActionCacheEvent.Error)
@@ -90,6 +90,21 @@ object ActionCache:
             if paths.isEmpty then organicTask
             else valueFromStr(IO.read(paths.head.toFile()), result.origin)
       case Left(_) => organicTask
+
+  /**
+   * Represents a value and output files, used internally by the macro.
+   */
+  class InternalActionResult[A1] private (
+      val value: A1,
+      val outputs: Seq[VirtualFile],
+  )
+  end InternalActionResult
+  object InternalActionResult:
+    def apply[A1](value: A1, outputs: Seq[VirtualFile]): InternalActionResult[A1] =
+      new InternalActionResult(value, outputs)
+    private[sbt] def unapply[A1](r: InternalActionResult[A1]): Option[(A1, Seq[VirtualFile])] =
+      Some(r.value, r.outputs)
+  end InternalActionResult
 end ActionCache
 
 class BuildWideCacheConfiguration(

util-cache/src/test/scala/sbt/util/ActionCacheTest.scala

@@ -11,6 +11,7 @@ import xsbti.VirtualFileRef
 import java.nio.file.Path
 import java.nio.file.Paths
 import java.nio.file.Files
+import ActionCache.InternalActionResult
 
 object ActionCacheTest extends BasicTestSuite:
   val tags = CacheLevelTag.all.toList
@@ -35,9 +36,9 @@ object ActionCacheTest extends BasicTestSuite:
   def testActionCacheBasic(cache: ActionCacheStore): Unit =
     import sjsonnew.BasicJsonProtocol.*
     var called = 0
-    val action: ((Int, Int)) => (Int, Seq[VirtualFile]) = { case (a, b) =>
+    val action: ((Int, Int)) => InternalActionResult[Int] = { case (a, b) =>
       called += 1
-      (a + b, Nil)
+      InternalActionResult(a + b, Nil)
     }
     IO.withTemporaryDirectory: (tempDir) =>
       val config = getCacheConfig(cache, tempDir)
@@ -57,10 +58,10 @@ object ActionCacheTest extends BasicTestSuite:
     import sjsonnew.BasicJsonProtocol.*
     IO.withTemporaryDirectory: (tempDir) =>
       var called = 0
-      val action: ((Int, Int)) => (Int, Seq[VirtualFile]) = { case (a, b) =>
+      val action: ((Int, Int)) => InternalActionResult[Int] = { case (a, b) =>
         called += 1
         val out = StringVirtualFile1(s"$tempDir/a.txt", (a + b).toString)
-        (a + b, Seq(out))
+        InternalActionResult(a + b, Seq(out))
       }
       val config = getCacheConfig(cache, tempDir)
       val v1 =