Re-run things when users press enter in watch mode (#1451)

Like how Mill does

Author: alexarchambault

modules/cli/src/main/scala/scala/cli/commands/Compile.scala

@@ -97,7 +97,7 @@ object Compile extends ScalaCommand[CompileOptions] with BuildCommandHelpers {
         for (builds <- res.orReport(logger))
           postBuild(builds, allowExit = false)
       }
-      try WatchUtil.waitForCtrlC()
+      try WatchUtil.waitForCtrlC(() => watcher.schedule())
       finally watcher.dispose()
     }
     else {

modules/cli/src/main/scala/scala/cli/commands/Package.scala

@@ -104,7 +104,7 @@ object Package extends ScalaCommand[PackageOptions] with BuildCommandHelpers {
             System.err.println("Build cancelled")
         }
       }
-      try WatchUtil.waitForCtrlC()
+      try WatchUtil.waitForCtrlC(() => watcher.schedule())
       finally watcher.dispose()
     }
     else {

modules/cli/src/main/scala/scala/cli/commands/Repl.scala

@@ -126,17 +126,23 @@ object Repl extends ScalaCommand[ReplOptions] {
 
     if (inputs.isEmpty) {
       val artifacts = initialBuildOptions.artifacts(logger, Scope.Main).orExit(logger)
-      doRunRepl(
-        initialBuildOptions,
-        artifacts,
-        None,
-        allowExit = !options.sharedRepl.watch.watchMode,
-        buildOpt = None
-      )
+      // synchronizing, so that multiple presses to enter (handled by WatchUtil.waitForCtrlC)
+      // don't try to run repls in parallel
+      val lock = new Object
+      def runThing() = lock.synchronized {
+        doRunRepl(
+          initialBuildOptions,
+          artifacts,
+          None,
+          allowExit = !options.sharedRepl.watch.watchMode,
+          buildOpt = None
+        )
+      }
+      runThing()
       if (options.sharedRepl.watch.watchMode) {
         // nothing to watch, just wait for Ctrl+C
         WatchUtil.printWatchMessage()
-        WatchUtil.waitForCtrlC()
+        WatchUtil.waitForCtrlC(() => runThing())
       }
     }
     else if (options.sharedRepl.watch.watchMode) {
@@ -159,7 +165,7 @@ object Repl extends ScalaCommand[ReplOptions] {
             case _: Build.Cancelled  => buildCancelled(allowExit = false)
           }
       }
-      try WatchUtil.waitForCtrlC()
+      try WatchUtil.waitForCtrlC(() => watcher.schedule())
       finally watcher.dispose()
     }
     else {

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

@@ -230,7 +230,7 @@ object Run extends ScalaCommand[RunOptions] with BuildCommandHelpers {
             System.err.println("Compilation failed")
         }
       }
-      try WatchUtil.waitForCtrlC()
+      try WatchUtil.waitForCtrlC(() => watcher.schedule())
       finally watcher.dispose()
     }
     else {

modules/cli/src/main/scala/scala/cli/commands/Test.scala

@@ -137,7 +137,7 @@ object Test extends ScalaCommand[TestOptions] {
         for (builds <- res.orReport(logger))
           maybeTest(builds, allowExit = false)
       }
-      try WatchUtil.waitForCtrlC()
+      try WatchUtil.waitForCtrlC(() => watcher.schedule())
       finally watcher.dispose()
     }
     else {

modules/cli/src/main/scala/scala/cli/commands/WatchUtil.scala

@@ -17,7 +17,14 @@ object WatchUtil {
   def printWatchMessage(): Unit =
     System.err.println(waitMessage("Watching sources"))
 
-  def waitForCtrlC(): Unit =
-    while (System.in.read() != -1) {}
+  def waitForCtrlC(onPressEnter: () => Unit = () => ()): Unit = {
+    var readKey = -1
+    while ({
+      readKey = System.in.read()
+      readKey != -1
+    })
+      if (readKey == '\n')
+        onPressEnter()
+  }
 
 }

modules/cli/src/main/scala/scala/cli/commands/publish/Publish.scala

@@ -276,7 +276,7 @@ object Publish extends ScalaCommand[PublishOptions] with BuildCommandHelpers {
           )
         }
       }
-      try WatchUtil.waitForCtrlC()
+      try WatchUtil.waitForCtrlC(() => watcher.schedule())
       finally watcher.dispose()
     }
     else {