Ensure scala-cli.sh logs to stderr

build.mill

@@ -169,6 +169,8 @@ object integration extends CliIntegration {
 object `docs-tests` extends Cross[DocsTests](Scala.scala3MainVersions)
     with CrossScalaDefaultToInternal
 
+def scalaCliSh = Task.Source("scala-cli.sh")
+
 trait DocsTests extends CrossSbtModule with ScalaCliScalafixModule with LocatedInModules
     with HasTests { main =>
   override def mvnDeps: T[Seq[Dep]] = Seq(
@@ -1037,7 +1039,8 @@ trait CliIntegration extends SbtModule
     override def forkEnv: T[Map[String, String]] = super.forkEnv() ++ Seq(
       "SCALA_CLI_TMP"                -> tmpDirBase().path.toString,
       "SCALA_CLI_PRINT_STACK_TRACES" -> "1",
-      "SCALA_CLI_CONFIG"             -> (tmpDirBase().path / "config" / "config.json").toString
+      "SCALA_CLI_CONFIG"             -> (tmpDirBase().path / "config" / "config.json").toString,
+      "SCALA_CLI_SHELL_LAUNCHER"     -> scalaCliSh().path.toString
     )
 
     def constantsFile: T[PathRef] = Task(persistent = true) {

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

@@ -0,0 +1,63 @@
+package scala.cli.integration
+
+import com.eed3si9n.expecty.Expecty.expect
+
+import scala.concurrent.duration.{Duration, DurationInt}
+import scala.util.Properties
+
+class ShellLauncherTests extends ScalaCliSuite {
+
+  // downloading the launcher + a JVM + the compiler on a cold cache can take a while
+  override def munitTimeout: Duration =
+    10.minutes
+
+  private lazy val launcherScript: os.Path = {
+    val path = Option(System.getenv("SCALA_CLI_SHELL_LAUNCHER")).getOrElse {
+      sys.error("SCALA_CLI_SHELL_LAUNCHER not set")
+    }
+    os.Path(path)
+  }
+
+  private def hasCachedLaunchers(cache: os.Path): Boolean =
+    os.walk(cache).exists { p =>
+      val subPath = p.subRelativeTo(cache)
+      p.last.startsWith("scala-cli-") && subPath.segments.contains("github.com") && os.isFile(p)
+    }
+
+  if (!Properties.isWin)
+    test("only the app output goes to stdout") {
+      stdoutTest()
+    }
+
+  def stdoutTest(): Unit = {
+    val appMessage = "Hello from the dummy app"
+    val appRelPath = os.rel / "app.sc"
+
+    TestInputs(
+      appRelPath -> s"""println("$appMessage")"""
+    ).fromRoot { root =>
+      val cache = root / "cs-cache"
+      os.makeDir.all(cache)
+
+      // sanity check: the launcher really isn't in the cache to begin with
+      expect(!hasCachedLaunchers(cache))
+
+      def runLauncher(): os.CommandResult =
+        os.proc(launcherScript, "run", "--server=false", appRelPath).call(
+          cwd = root,
+          env = Map("COURSIER_CACHE" -> cache.toString)
+        )
+
+      val res = runLauncher()
+
+      // the launcher's own messages (e.g. "Downloading ...") must not leak to stdout
+      expect(res.out.trim() == appMessage)
+      // the launcher got downloaded under COURSIER_CACHE
+      expect(hasCachedLaunchers(cache))
+
+      // second run, with the launcher already present in the cache
+      val res1 = runLauncher()
+      expect(res1.out.trim() == appMessage)
+    }
+  }
+}

scala-cli.sh

@@ -23,23 +23,23 @@ if [ "$(expr substr $(uname -s) 1 5 2>/dev/null)" == "Linux" ]; then
   if [[ "$arch" == "aarch64" ]] || [[ "$arch" == "x86_64" ]]; then
     SCALA_CLI_URL="https://github.com/$GH_ORG/$GH_NAME/releases/download/$TAG/scala-cli-${arch}-pc-linux.gz"
   else
-    echoerr "scala-cli is not supported on $arch"
+    echo "scala-cli is not supported on $arch" 1>&2
     exit 2
   fi
-  CACHE_BASE="$HOME/.cache/coursier/v1"
+  CACHE_BASE="${COURSIER_CACHE:-"$HOME/.cache/coursier/v1"}"
 elif [ "$(uname)" == "Darwin" ]; then
   arch=$(uname -m)
-  CACHE_BASE="$HOME/Library/Caches/Coursier/v1"
+  CACHE_BASE="${COURSIER_CACHE:-"$HOME/Library/Caches/Coursier/v1"}"
   if [[ "$arch" == "x86_64" ]]; then
     SCALA_CLI_URL="https://github.com/$GH_ORG/$GH_NAME/releases/download/$TAG/scala-cli-x86_64-apple-darwin.gz"
   elif [[ "$arch" == "arm64" ]]; then
     SCALA_CLI_URL="https://github.com/$GH_ORG/$GH_NAME/releases/download/$TAG/scala-cli-aarch64-apple-darwin.gz"
   else
-    echoerr "scala-cli is not supported on $arch"
+    echo "scala-cli is not supported on $arch" 1>&2
     exit 2
   fi
 else
-  echo "This standalone scala-cli launcher is supported only in Linux and macOS. If you are using Windows, please use the dedicated launcher scala-cli.bat"
+  echo "This standalone scala-cli launcher is supported only in Linux and macOS. If you are using Windows, please use the dedicated launcher scala-cli.bat" 1>&2
   exit 1
 fi
 
@@ -49,7 +49,7 @@ SCALA_CLI_BIN_PATH=${CACHE_DEST%.gz}
 if [ ! -f "$CACHE_DEST" ]; then
   mkdir -p "$(dirname "$CACHE_DEST")"
   TMP_DEST="$CACHE_DEST.tmp-setup"
-  echo "Downloading $SCALA_CLI_URL"
+  echo "Downloading $SCALA_CLI_URL" 1>&2
   curl -fLo "$TMP_DEST" "$SCALA_CLI_URL"
   mv "$TMP_DEST" "$CACHE_DEST"
 fi