Add a command line option & directive for enabling/disabling Scala Na…

…tive multithreading (#3011)

modules/build/src/test/scala/scala/build/tests/ScalaNativeUsingDirectiveTests.scala

@@ -236,4 +236,17 @@ class ScalaNativeUsingDirectiveTests extends TestUtil.ScalaCliBuildSuite {
       )
     }
   }
+
+  for { multithreadingDirective <- Seq("`native-multithreading`", "nativeMultithreading") }
+    test(s"ScalaNativeOptions for $multithreadingDirective") {
+      val inputs = TestInputs(
+        os.rel / "p.sc" ->
+          s"""//> using $multithreadingDirective
+             |def foo() = println("hello foo")
+             |""".stripMargin
+      )
+      inputs.withLoadedBuild(buildOptions, buildThreads, bloopConfig) { (_, _, maybeBuild) =>
+        assert(maybeBuild.options.scalaNativeOptions.multithreading.get)
+      }
+    }
 }

modules/cli/src/main/scala/scala/cli/commands/shared/ScalaNativeOptions.scala

@@ -70,7 +70,12 @@ final case class ScalaNativeOptions(
   @Group(HelpGroup.ScalaNative.toString)
   @HelpMessage("Embed resources into the Scala Native binary (can be read with the Java resources API)")
    @Tag(tags.should)
-    embedResources: Option[Boolean] = None
+    embedResources: Option[Boolean] = None,
+
+  @Group(HelpGroup.ScalaNative.toString)
+  @HelpMessage("Enable/disable Scala Native multithreading support")
+  @Tag(tags.should)
+    nativeMultithreading: Option[Boolean] = None
 
 )
 // format: on

modules/cli/src/main/scala/scala/cli/commands/shared/SharedOptions.scala

@@ -285,6 +285,7 @@ final case class SharedOptions(
       compileDefaults = nativeCompileDefaults,
       embedResources = embedResources,
       buildTargetStr = nativeTarget,
+      multithreading = nativeMultithreading,
       maxDefaultNativeVersions = maxDefaultScalaNativeVersions
     )
   }

modules/directives/src/main/scala/scala/build/preprocessing/directives/ScalaNative.scala

@@ -46,6 +46,7 @@ final case class ScalaNative(
     nativeClangPP: Option[String] = None,
   nativeEmbedResources: Option[Boolean] = None,
   nativeTarget: Option[String] = None,
+  nativeMultithreading: Option[Boolean] = None
 ) extends HasBuildOptions {
   // format: on
   def buildOptions: Either[BuildException, BuildOptions] = {
@@ -59,7 +60,8 @@ final case class ScalaNative(
       clang = nativeClang,
       clangpp = nativeClangPP,
       embedResources = nativeEmbedResources,
-      buildTargetStr = nativeTarget
+      buildTargetStr = nativeTarget,
+      multithreading = nativeMultithreading
     )
     val buildOpt = BuildOptions(scalaNativeOptions = nativeOptions)
     Right(buildOpt)

modules/integration/src/test/scala/scala/cli/integration/RunScalaNativeTestDefinitions.scala

@@ -401,4 +401,60 @@ trait RunScalaNativeTestDefinitions { _: RunTestDefinitions =>
         }
       }
     }
+
+  for {
+    expectedMultithreadingState <- Seq(true, false)
+    // multithreading should be enabled by Scala Native by default
+    setExplicitly <- if (expectedMultithreadingState) Seq(true, false) else Seq(true)
+    useDirective  <- if (setExplicitly) Seq(true, false) else Seq(false)
+    directive =
+      if (useDirective && setExplicitly)
+        s"//> using nativeMultithreading $expectedMultithreadingState"
+      else ""
+    cliOptions =
+      if (!useDirective && setExplicitly)
+        Seq(s"--native-multithreading=$expectedMultithreadingState")
+      else Nil
+    testDescriptionString = useDirective -> setExplicitly match {
+      case (_, false)    => "(implicitly)"
+      case (true, true)  => "with directive"
+      case (false, true) => "with command line option"
+    }
+  }
+    test(
+      s"Scala Native multithreading set to $expectedMultithreadingState $testDescriptionString"
+    ) {
+      val fileName       = "multithreading.sc"
+      val expectedOutput = "42"
+      val threadSleep    = "100"
+      val threadAwait    = "2.seconds"
+      val inputs = TestInputs(
+        os.rel / fileName ->
+          s"""$directive
+             |import scala.concurrent._
+             |import scala.concurrent.duration._
+             |import ExecutionContext.Implicits.global
+             |val promise = Promise[Int]()
+             |val thread = new Thread(new Runnable {
+             |    def run(): Unit = {
+             |      Thread.sleep($threadSleep)
+             |      promise.success($expectedOutput)
+             |    }
+             |  })
+             |thread.start()
+             |val result = Await.result(promise.future, $threadAwait)
+             |println(result)
+             |""".stripMargin
+      )
+      inputs.fromRoot { root =>
+        val r = os.proc(TestUtil.cli, extraOptions, fileName, "--native", cliOptions)
+          .call(cwd = root, stderr = os.Pipe, check = expectedMultithreadingState)
+        if (!expectedMultithreadingState) expect(r.exitCode == 1)
+        else {
+          expect(r.exitCode == 0)
+          expect(r.out.trim() == expectedOutput)
+        }
+        expect(r.err.trim().contains(s"multithreadingEnabled=$expectedMultithreadingState"))
+      }
+    }
 }

modules/options/src/main/scala/scala/build/options/ScalaNativeOptions.scala

@@ -40,6 +40,7 @@ final case class ScalaNativeOptions(
   compileDefaults: Option[Boolean] = None,
   embedResources: Option[Boolean] = None,
   buildTargetStr: Option[String] = None,
+  multithreading: Option[Boolean] = None,
   maxDefaultNativeVersions: List[(String, String)] = Nil
 ) {
 
@@ -122,6 +123,9 @@ final case class ScalaNativeOptions(
       }
     else Nil
 
+  private def multithreadingCliOption(): List[String] =
+    multithreading.toList.flatMap(m => List("--multithreading", m.toString))
+
   def platformSuffix: String =
     "native" + ScalaVersion.nativeBinary(finalVersion).getOrElse(finalVersion)
 
@@ -174,7 +178,8 @@ final case class ScalaNativeOptions(
       linkingCliOptions() ++
       compileCliOptions() ++
       resourcesCliOptions(resourcesExist) ++
-      targetCliOption()
+      targetCliOption() ++
+      multithreadingCliOption()
 
 }
 

website/docs/reference/cli-options.md

@@ -1396,6 +1396,10 @@ Build target type
 
 Embed resources into the Scala Native binary (can be read with the Java resources API)
 
+### `--native-multithreading`
+
+Enable/disable Scala Native multithreading support
+
 ## Scalac options
 
 Available in commands:

website/docs/reference/scala-command/cli-options.md

@@ -900,6 +900,12 @@ Build target type
 
 Embed resources into the Scala Native binary (can be read with the Java resources API)
 
+### `--native-multithreading`
+
+`SHOULD have` per Scala Runner specification
+
+Enable/disable Scala Native multithreading support
+
 ## Scalac options
 
 Available in commands:

website/docs/reference/scala-command/runner-specification.md

@@ -204,6 +204,10 @@ Build target type
 
 Embed resources into the Scala Native binary (can be read with the Java resources API)
 
+**--native-multithreading**
+
+Enable/disable Scala Native multithreading support
+
 **--repository**
 
 Add repositories for dependency resolution.
@@ -967,6 +971,10 @@ Build target type
 
 Embed resources into the Scala Native binary (can be read with the Java resources API)
 
+**--native-multithreading**
+
+Enable/disable Scala Native multithreading support
+
 **--repository**
 
 Add repositories for dependency resolution.
@@ -1532,6 +1540,10 @@ Build target type
 
 Embed resources into the Scala Native binary (can be read with the Java resources API)
 
+**--native-multithreading**
+
+Enable/disable Scala Native multithreading support
+
 **--repository**
 
 Add repositories for dependency resolution.
@@ -2129,6 +2141,10 @@ Build target type
 
 Embed resources into the Scala Native binary (can be read with the Java resources API)
 
+**--native-multithreading**
+
+Enable/disable Scala Native multithreading support
+
 **--repository**
 
 Add repositories for dependency resolution.
@@ -2739,6 +2755,10 @@ Build target type
 
 Embed resources into the Scala Native binary (can be read with the Java resources API)
 
+**--native-multithreading**
+
+Enable/disable Scala Native multithreading support
+
 **--repository**
 
 Add repositories for dependency resolution.
@@ -3325,6 +3345,10 @@ Build target type
 
 Embed resources into the Scala Native binary (can be read with the Java resources API)
 
+**--native-multithreading**
+
+Enable/disable Scala Native multithreading support
+
 **--repository**
 
 Add repositories for dependency resolution.
@@ -3948,6 +3972,10 @@ Build target type
 
 Embed resources into the Scala Native binary (can be read with the Java resources API)
 
+**--native-multithreading**
+
+Enable/disable Scala Native multithreading support
+
 **--repository**
 
 Add repositories for dependency resolution.
@@ -4622,6 +4650,10 @@ Build target type
 
 Embed resources into the Scala Native binary (can be read with the Java resources API)
 
+**--native-multithreading**
+
+Enable/disable Scala Native multithreading support
+
 **--repository**
 
 Add repositories for dependency resolution.
@@ -5537,6 +5569,10 @@ Build target type
 
 Embed resources into the Scala Native binary (can be read with the Java resources API)
 
+**--native-multithreading**
+
+Enable/disable Scala Native multithreading support
+
 **--repository**
 
 Add repositories for dependency resolution.