Swap shared vars for AtomicReferences

Author: MaciejG604

modules/cli/src/main/scala/scala/cli/commands/run/Run.scala

@@ -7,6 +7,7 @@ import caseapp.core.help.HelpFormat
 import java.io.File
 import java.util.Locale
 import java.util.concurrent.CompletableFuture
+import java.util.concurrent.atomic.AtomicReference
 
 import scala.build.EitherCps.{either, value}
 import scala.build.*
@@ -229,18 +230,18 @@ object Run extends ScalaCommand[RunOptions] with BuildCommandHelpers {
  /** A handle to the Runner process, used to kill the process if it's still alive when a change
  * occured and restarts are allowed or to wait for it if restarts are not allowed
  */
- var processOpt = Option.empty[(Process, CompletableFuture[_])]
+ val processOpt = AtomicReference(Option.empty[(Process, CompletableFuture[_])])
 
  /** shouldReadInput controls whether [[WatchUtil.waitForCtrlC]](that's keeping the main thread
  * alive) should try to read StdIn or just call wait()
  */
- var shouldReadInput = false
+ val shouldReadInput = AtomicReference(false)
 
- /** a handle to the main thread to interrupt its operations when:
+ /** A handle to the main thread to interrupt its operations when:
  * - it's blocked on reading StdIn, and it's no longer required
  * - it's waiting and should start reading StdIn
  */
- var mainThreadOpt = Option.empty[Thread]
+ val mainThreadOpt = AtomicReference(Option.empty[Thread])
 
  val watcher = Build.watch(
  inputs,
@@ -253,22 +254,22 @@ object Run extends ScalaCommand[RunOptions] with BuildCommandHelpers {
  partial = None,
  actionableDiagnostics = actionableDiagnostics,
  postAction = () =>
- if (processOpt.exists(_._1.isAlive()))
+ if (processOpt.get().exists(_._1.isAlive()))
  WatchUtil.printWatchWhileRunningMessage()
  else
  WatchUtil.printWatchMessage()
  ) { res =>
- for ((process, onExitProcess) <- processOpt) {
+ for ((process, onExitProcess) <- processOpt.get()) {
  onExitProcess.cancel(true)
  ProcUtil.interruptProcess(process, logger)
  }
  res.orReport(logger).map(_.main).foreach {
  case s: Build.Successful =>
- for ((proc, _) <- processOpt if proc.isAlive)
+ for ((proc, _) <- processOpt.get() if proc.isAlive)
  // If the process doesn't exit, send SIGKILL
  ProcUtil.forceKillProcess(proc, logger)
- shouldReadInput = false
- mainThreadOpt.foreach(_.interrupt())
+ shouldReadInput.set(false)
+ mainThreadOpt.get().foreach(_.interrupt())
  val maybeProcess = maybeRun(
  s,
  allowTerminate = false,
@@ -282,29 +283,36 @@ object Run extends ScalaCommand[RunOptions] with BuildCommandHelpers {
  case (proc, onExit) =>
  if (options.sharedRun.watch.restart)
  onExit.thenApply { _ =>
- shouldReadInput = true
- mainThreadOpt.foreach(_.interrupt())
+ shouldReadInput.set(true)
+ mainThreadOpt.get().foreach(_.interrupt())
  }
  (proc, onExit)
  }
  s.copyOutput(options.shared)
  if (options.sharedRun.watch.restart)
- processOpt = maybeProcess
+ processOpt.set(maybeProcess)
  else {
  for ((proc, onExit) <- maybeProcess)
  ProcUtil.waitForProcess(proc, onExit)
- shouldReadInput = true
- mainThreadOpt.foreach(_.interrupt())
+ shouldReadInput.set(true)
+ mainThreadOpt.get().foreach(_.interrupt())
  }
  case _: Build.Failed =>
  System.err.println("Compilation failed")
  }
  }
- mainThreadOpt = Some(Thread.currentThread())
-
- try WatchUtil.waitForCtrlC(() => watcher.schedule(), () => shouldReadInput)
+ mainThreadOpt.set(Some(Thread.currentThread()))
+
+ try
+ WatchUtil.waitForCtrlC(
+ { () =>
+ watcher.schedule()
+ shouldReadInput.set(false)
+ },
+ () => shouldReadInput.get()
+ )
  finally {
- mainThreadOpt = None
+ mainThreadOpt.set(None)
  watcher.dispose()
  }
  }