Merge pull request #1369 from Gedochao/backwards-compat-classpat-and-…

…main-class-inputs

Make inputs optional when `-classpath` and `--main-class` are passed

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

@@ -57,7 +57,8 @@ object Build {
     def outputOpt: Some[os.Path]          = Some(output)
     def dependencyClassPath: Seq[os.Path] = sources.resourceDirs ++ artifacts.classPath
     def fullClassPath: Seq[os.Path]       = Seq(output) ++ dependencyClassPath
-    def foundMainClasses(): Seq[String]   = MainClass.find(output)
+    def foundMainClasses(): Seq[String] =
+      MainClass.find(output) ++ options.classPathOptions.extraClassPath.flatMap(MainClass.find)
     def retainedMainClass(
       mainClasses: Seq[String],
       commandString: String,

modules/build/src/main/scala/scala/build/Inputs.scala

@@ -302,10 +302,11 @@ object Inputs {
     directories: Directories,
     forcedWorkspace: Option[os.Path],
     enableMarkdown: Boolean,
-    allowRestrictedFeatures: Boolean
+    allowRestrictedFeatures: Boolean,
+    extraClasspathWasPassed: Boolean
   ): Inputs = {
 
-    assert(validElems.nonEmpty)
+    assert(extraClasspathWasPassed || validElems.nonEmpty)
 
     val (inferredWorkspace, inferredNeedsHash, workspaceOrigin) = {
       val settingsFiles = projectSettingsFiles(validElems)
@@ -490,7 +491,8 @@ object Inputs {
     acceptFds: Boolean,
     forcedWorkspace: Option[os.Path],
     enableMarkdown: Boolean,
-    allowRestrictedFeatures: Boolean
+    allowRestrictedFeatures: Boolean,
+    extraClasspathWasPassed: Boolean
   ): Either[BuildException, Inputs] = {
     val validatedArgs: Seq[Either[String, Seq[Element]]] =
       validateArgs(args, cwd, download, stdinOpt, acceptFds)
@@ -504,15 +506,16 @@ object Inputs {
       val validElems = validatedArgsAndSnippets.collect {
         case Right(elem) => elem
       }.flatten
-      assert(validElems.nonEmpty)
+      assert(extraClasspathWasPassed || validElems.nonEmpty)
 
       Right(forValidatedElems(
         validElems,
         baseProjectName,
         directories,
         forcedWorkspace,
         enableMarkdown,
-        allowRestrictedFeatures
+        allowRestrictedFeatures,
+        extraClasspathWasPassed
       ))
     }
     else
@@ -533,10 +536,11 @@ object Inputs {
     acceptFds: Boolean = false,
     forcedWorkspace: Option[os.Path] = None,
     enableMarkdown: Boolean = false,
-    allowRestrictedFeatures: Boolean
+    allowRestrictedFeatures: Boolean,
+    extraClasspathWasPassed: Boolean
   ): Either[BuildException, Inputs] =
     if (
-      args.isEmpty && scriptSnippetList.isEmpty && scalaSnippetList.isEmpty && javaSnippetList.isEmpty
+      args.isEmpty && scriptSnippetList.isEmpty && scalaSnippetList.isEmpty && javaSnippetList.isEmpty && !extraClasspathWasPassed
     )
       defaultInputs().toRight(new InputsException(
         "No inputs provided (expected files with .scala, .sc, .java or .md extensions, and / or directories)."
@@ -555,7 +559,8 @@ object Inputs {
         acceptFds,
         forcedWorkspace,
         enableMarkdown,
-        allowRestrictedFeatures
+        allowRestrictedFeatures,
+        extraClasspathWasPassed
       )
 
   def default(): Option[Inputs] =

modules/build/src/main/scala/scala/build/internal/MainClass.scala

@@ -1,6 +1,7 @@
 package scala.build.internal
 
 import org.objectweb.asm
+import org.objectweb.asm.ClassReader
 
 object MainClass {
 
@@ -36,20 +37,27 @@ object MainClass {
       if (foundMainClass) nameOpt else None
   }
 
+  def findInClass(path: os.Path): Iterator[String] = {
+    val is = os.read.inputStream(path)
+    try {
+      val reader  = new ClassReader(is)
+      val checker = new MainMethodChecker
+      reader.accept(checker, 0)
+      checker.mainClassOpt.iterator
+    }
+    finally is.close()
+  }
   def find(output: os.Path): Seq[String] =
-    os.walk(output)
-      .iterator
-      .filter(os.isFile(_))
-      .filter(_.last.endsWith(".class"))
-      .flatMap { path =>
-        val is = os.read.inputStream(path)
-        try {
-          val reader  = new asm.ClassReader(is)
-          val checker = new MainMethodChecker
-          reader.accept(checker, 0)
-          checker.mainClassOpt.iterator
-        }
-        finally is.close()
-      }
-      .toVector
+    output match {
+      case o if os.isFile(o) && o.last.endsWith(".class") =>
+        findInClass(o).toVector
+      case o if os.isDir(o) =>
+        os.walk(o)
+          .iterator
+          .filter(os.isFile(_))
+          .filter(_.last.endsWith(".class"))
+          .flatMap(findInClass)
+          .toVector
+      case _ => Vector.empty
+    }
 }

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

@@ -43,7 +43,8 @@ final case class TestInputs(
         tmpDir,
         Directories.under(tmpDir / ".data"),
         forcedWorkspace = forcedWorkspaceOpt.map(_.resolveFrom(tmpDir)),
-        allowRestrictedFeatures = true
+        allowRestrictedFeatures = true,
+        extraClasspathWasPassed = false
       )
       res match {
         case Left(err)     => throw new Exception(err)

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

@@ -17,7 +17,8 @@ object Clean extends ScalaCommand[CleanOptions] {
       options.directories.directories,
       defaultInputs = () => Inputs.default(),
       forcedWorkspace = options.workspace.forcedWorkspaceOpt,
-      allowRestrictedFeatures = ScalaCli.allowRestrictedFeatures
+      allowRestrictedFeatures = ScalaCli.allowRestrictedFeatures,
+      extraClasspathWasPassed = false
     ) match {
       case Left(message) =>
         System.err.println(message)

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

@@ -34,7 +34,8 @@ class Default(
       {
         val shouldDefaultToRun =
           args.remaining.nonEmpty || options.shared.snippet.executeScript.nonEmpty ||
-          options.shared.snippet.executeScala.nonEmpty || options.shared.snippet.executeJava.nonEmpty
+          options.shared.snippet.executeScala.nonEmpty || options.shared.snippet.executeJava.nonEmpty ||
+          (options.shared.extraJarsAndClasspath.nonEmpty && options.sharedRun.mainClass.mainClass.nonEmpty)
         if shouldDefaultToRun then RunOptions.parser else ReplOptions.parser
       }.parse(rawArgs) match
         case Left(e)                              => error(e)

modules/cli/src/main/scala/scala/cli/commands/util/SharedOptionsUtil.scala

@@ -61,7 +61,8 @@ object SharedOptionsUtil extends CommandHelpers {
     scriptSnippetList: List[String],
     scalaSnippetList: List[String],
     javaSnippetList: List[String],
-    enableMarkdown: Boolean = false
+    enableMarkdown: Boolean = false,
+    extraClasspathWasPassed: Boolean = false
   ): Either[BuildException, Inputs] = {
     val resourceInputs = resourceDirs
       .map(os.Path(_, Os.pwd))
@@ -84,7 +85,8 @@ object SharedOptionsUtil extends CommandHelpers {
       acceptFds = !Properties.isWin,
       forcedWorkspace = forcedWorkspaceOpt,
       enableMarkdown = enableMarkdown,
-      allowRestrictedFeatures = ScalaCli.allowRestrictedFeatures
+      allowRestrictedFeatures = ScalaCli.allowRestrictedFeatures,
+      extraClasspathWasPassed = extraClasspathWasPassed
     )
     maybeInputs.map { inputs =>
       val forbiddenDirs =
@@ -367,7 +369,8 @@ object SharedOptionsUtil extends CommandHelpers {
         scriptSnippetList = allScriptSnippets,
         scalaSnippetList = allScalaSnippets,
         javaSnippetList = allJavaSnippets,
-        enableMarkdown = v.markdown.enableMarkdown
+        enableMarkdown = v.markdown.enableMarkdown,
+        extraClasspathWasPassed = v.extraJarsAndClasspath.nonEmpty
       )
 
     def allScriptSnippets: List[String] = v.snippet.scriptSnippet ++ v.snippet.executeScript

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

@@ -6,7 +6,7 @@ class DefaultTests extends ScalaCliSuite {
   test("running scala-cli with no args should default to repl") {
     TestInputs.empty.fromRoot { root =>
       val res = os.proc(TestUtil.cli, "--repl-dry-run").call(cwd = root, mergeErrIntoOut = true)
-      expect(res.out.trim() == "Dry run, not running REPL.")
+      expect(res.out.trim() == replDryRunOutput)
     }
   }
   test("running scala-cli with no args should not accept run-only options") {
@@ -94,11 +94,66 @@ class DefaultTests extends ScalaCliSuite {
     }
   }
 
+  test("default to the run sub-command if -classpath and --main-class are passed") {
+    val expectedOutput = "Hello"
+    val mainClassName  = "Main"
+    TestInputs(
+      os.rel / s"$mainClassName.scala" -> s"""object $mainClassName extends App { println("$expectedOutput") }"""
+    ).fromRoot { (root: os.Path) =>
+      val compilationOutputDir = os.rel / "compilationOutput"
+      // first, precompile to an explicitly specified output directory with -d
+      os.proc(
+        TestUtil.cli,
+        ".",
+        "-d",
+        compilationOutputDir
+      ).call(cwd = root)
+
+      // next, run while relying on the pre-compiled class instead of passing inputs
+      val runRes = os.proc(
+        TestUtil.cli,
+        "--main-class",
+        mainClassName,
+        "-classpath",
+        (os.rel / compilationOutputDir).toString
+      ).call(cwd = root)
+      expect(runRes.out.trim == expectedOutput)
+    }
+  }
+
+  test("default to the repl sub-command if -classpath is passed, but --main-class isn't") {
+    val expectedOutput = "Hello"
+    val mainClassName  = "Main"
+    TestInputs(
+      os.rel / s"$mainClassName.scala" -> s"""object $mainClassName extends App { println("$expectedOutput") }"""
+    ).fromRoot { (root: os.Path) =>
+      val compilationOutputDir = os.rel / "compilationOutput"
+      // first, precompile to an explicitly specified output directory with -d
+      os.proc(
+        TestUtil.cli,
+        ".",
+        "-d",
+        compilationOutputDir
+      ).call(cwd = root)
+
+      // next, run the repl while relying on the pre-compiled classes
+      val runRes = os.proc(
+        TestUtil.cli,
+        "--repl-dry-run",
+        "-classpath",
+        (os.rel / compilationOutputDir).toString
+      ).call(cwd = root, mergeErrIntoOut = true)
+      expect(runRes.out.trim == replDryRunOutput)
+    }
+  }
+
   private def unrecognizedArgMessage(argName: String) =
     s"""
        |Unrecognized argument: $argName
        |
        |To list all available options, run
        |  ${Console.BOLD}${TestUtil.detectCliPath} --help${Console.RESET}
        |""".stripMargin.trim
+
+  private lazy val replDryRunOutput = "Dry run, not running REPL."
 }

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

@@ -2313,6 +2313,34 @@ abstract class RunTestDefinitions(val scalaVersionOpt: Option[String])
     }
   }
 
+  test("run main class from -classpath even when no explicit inputs are passed") {
+    val expectedOutput = "Hello"
+    TestInputs(
+      os.rel / "Main.scala" -> s"""object Main extends App { println("$expectedOutput") }"""
+    ).fromRoot { (root: os.Path) =>
+      val compilationOutputDir = os.rel / "compilationOutput"
+      // first, precompile to an explicitly specified output directory with -d
+      os.proc(
+        TestUtil.cli,
+        "compile",
+        ".",
+        "-d",
+        compilationOutputDir,
+        extraOptions
+      ).call(cwd = root)
+
+      // next, run while relying on the pre-compiled class instead of passing inputs
+      val runRes = os.proc(
+        TestUtil.cli,
+        "run",
+        "-classpath",
+        (os.rel / compilationOutputDir).toString,
+        extraOptions
+      ).call(cwd = root)
+      expect(runRes.out.trim == expectedOutput)
+    }
+  }
+
   if (actualScalaVersion.startsWith("3"))
     test("should throw exception for code compiled by scala 3.1.3") {
       val exceptionMsg = "Throw exception in Scala"