Watch the artifact files for changes too

So that users doing a publishLocal and using it from a watched Scala CLI
project get their Scala CLI build re-run upon newly locally published
stuff, for example.

Author: alexarchambault

modules/build/src/main/scala/scala/build/Build.scala

@@ -713,6 +713,26 @@ object Build {
           }
         }
       }
+
+      val artifacts = res
+        .map { builds =>
+          def artifacts(build: Build): Seq[os.Path] =
+            build.successfulOpt.toSeq.flatMap(_.artifacts.classPath)
+          val main = artifacts(builds.main)
+          val test = builds.get(Scope.Test).map(artifacts).getOrElse(Nil)
+          (main ++ test).distinct
+        }
+        .getOrElse(Nil)
+      for (artifact <- artifacts) {
+        val depth    = if (os.isFile(artifact)) -1 else Int.MaxValue
+        val watcher0 = watcher.newWatcher()
+        watcher0.register(artifact.toNIO, depth)
+        watcher0.addObserver {
+          onChangeBufferedObserver { _ =>
+            watcher.schedule()
+          }
+        }
+      }
     }
 
     try doWatch()

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

@@ -2,6 +2,8 @@ package scala.cli.integration
 
 import com.eed3si9n.expecty.Expecty.expect
 
+import scala.concurrent.ExecutionContext
+import scala.concurrent.duration.Duration
 import scala.util.Properties
 
 class RunTestsDefault extends RunTestDefinitions(scalaVersionOpt = None) {
@@ -64,4 +66,67 @@ class RunTestsDefault extends RunTestDefinitions(scalaVersionOpt = None) {
     }
   }
 
+  test("watch artifacts") {
+    val libSourcePath = os.rel / "lib" / "Messages.scala"
+    def libSource(hello: String) =
+      s"""//> using publish.organization "test-org"
+         |//> using publish.name "messages"
+         |//> using publish.version "0.1.0"
+         |
+         |package messages
+         |
+         |object Messages {
+         |  def hello(name: String) = s"$hello $$name"
+         |}
+         |""".stripMargin
+    val inputs = TestInputs(
+      libSourcePath -> libSource("Hello"),
+      os.rel / "app" / "TestApp.scala" ->
+        """//> using lib "test-org::messages:0.1.0"
+          |
+          |package testapp
+          |
+          |import messages.Messages
+          |
+          |@main
+          |def run(): Unit =
+          |  println(Messages.hello("user"))
+          |""".stripMargin
+    )
+    inputs.fromRoot { root =>
+      val testRepo = root / "test-repo"
+
+      def publishLib(): Unit =
+        os.proc(TestUtil.cli, "publish", "--publish-repo", testRepo, "lib")
+          .call(cwd = root)
+
+      publishLib()
+
+      val proc = os.proc(TestUtil.cli, "run", "app", "-w", "-r", testRepo.toNIO.toUri.toASCIIString)
+        .spawn(cwd = root)
+
+      try
+        TestUtil.withThreadPool("watch-artifacts-test", 2) { pool =>
+          val timeout = Duration("20 seconds")
+          val ec      = ExecutionContext.fromExecutorService(pool)
+
+          val output = TestUtil.readLine(proc.stdout, ec, timeout)
+          expect(output == "Hello user")
+
+          os.write.over(root / libSourcePath, libSource("Hola"))
+          publishLib()
+
+          val secondOutput = TestUtil.readLine(proc.stdout, ec, timeout)
+          expect(secondOutput == "Hola user")
+        }
+      finally
+        if (proc.isAlive()) {
+          proc.destroy()
+          Thread.sleep(200L)
+          if (proc.isAlive())
+            proc.destroyForcibly()
+        }
+    }
+  }
+
 }