7 files changed, 78 insertions, 14 deletions
diff --git a/examples/dotty-example/src/Main.scala b/examples/dotty-example/src/Main.scala
index 1963b51..fdc2068 100644
--- a/examples/dotty-example/src/Main.scala
+++ b/examples/dotty-example/src/Main.scala
@@ -1,5 +1,6 @@
+package dotty_example
 object Main extends Foo("Hello Dotty - trait parameters, yay"){
-  def main(args: Array[String]) = {  
+  def main(args: Array[String]): Unit = {
     println(hello)
 
     // Sanity check the classpath: this won't run if the dotty jar is not present.
diff --git a/examples/scalafmt-example/build/build.scala b/examples/scalafmt-example/build/build.scala
index a489616..b8a819b 100644
--- a/examples/scalafmt-example/build/build.scala
+++ b/examples/scalafmt-example/build/build.scala
@@ -1,7 +1,7 @@
 import cbt._
 import org.scalafmt.ScalafmtStyle
 
-class Build(val context: Context) extends BuildBuild with Scalafmt {
+class Build(val context: Context) extends BaseBuild with Scalafmt {
   override def compile = {
     scalafmt
     super.compile
diff --git a/plugins/uber-jar/src/UberJar.scala b/plugins/uber-jar/src/UberJar.scala
index c6815b4..3783367 100644
--- a/plugins/uber-jar/src/UberJar.scala
+++ b/plugins/uber-jar/src/UberJar.scala
@@ -13,7 +13,7 @@ trait UberJar extends BaseBuild {
     ExitCode.Success
   }
 
-  def uberJarMainClass: Option[String] = Some(runClass)
+  def uberJarMainClass: Option[String] = runClass
 
   def uberJarName: String = projectName + ".jar"
 
diff --git a/stage1/Stage1Lib.scala b/stage1/Stage1Lib.scala
index c427b77..5e65018 100644
--- a/stage1/Stage1Lib.scala
+++ b/stage1/Stage1Lib.scala
@@ -8,7 +8,7 @@ import java.nio.file._
 import java.nio.file.attribute.FileTime
 import javax.tools._
 import java.security._
-import java.util.{Set=>_,Map=>_,_}
+import java.util.{Set=>_,Map=>_,List=>_,_}
 import java.util.concurrent.ConcurrentHashMap
 import javax.xml.bind.annotation.adapters.HexBinaryAdapter
 
@@ -95,12 +95,6 @@ class Stage1Lib( val logger: Logger ) extends BaseLib{
 
   // ========== compilation / execution ==========
 
-  def runMainIfFound(cls: String, args: Seq[String], classLoader: ClassLoader ): ExitCode = {
-    if( classLoader.canLoad(cls) ){
-      runMain(cls, args, classLoader )
-    } else ExitCode.Success
-  }
-
   def runMain( cls: String, args: Seq[String], classLoader: ClassLoader, fakeInstance: Boolean = false ): ExitCode = {
     import java.lang.reflect.Modifier
     logger.lib(s"Running $cls.main($args) with classLoader: " ++ classLoader.toString)
@@ -118,6 +112,67 @@ class Stage1Lib( val logger: Logger ) extends BaseLib{
     }
   }
 
+  /** shows an interactive dialogue in the shell asking the user to pick one of many choices */
+  def pickOne[T]( msg: String, choices: Seq[T] )( show: T => String ): Option[T] = {
+    if(choices.size == 0) None else if(choices.size == 1) Some(choices.head) else {
+      Option(System.console).map{
+        console =>
+        val indexedChoices: Map[Int, T] = choices.zipWithIndex.toMap.mapValues(_+1).map(_.swap)
+        System.err.println(
+          indexedChoices.map{ case (index,choice) => s"[${index}] "++show(choice)}.mkString("\n")
+        )
+        val range = s"1 - ${indexedChoices.size}"
+        System.err.println()
+        System.err.println( msg ++ " [" ++ range ++ "] " )
+        val answer = console.readLine()
+        val choice = try{
+          Some(Integer.parseInt(answer))
+        }catch{
+          case e:java.lang.NumberFormatException => None
+        }
+
+        choice.flatMap(indexedChoices.get).orElse{
+          System.err.println("Not in range "++range)
+          None
+        }
+      }.getOrElse{
+        System.err.println("Using '"++show(choices.head)++"' because System.console() == null. Use `cbt direct <task>` or see https://github.com/cvogt/cbt/issues/236")
+        None
+      }
+    }
+  }
+
+  /** interactively pick one main class */
+  def runClass( mainClasses: Seq[Class[_]] ): Option[Class[_]] = {
+    pickOne( "Which one do you want to run?", mainClasses )( _.toString )
+  }
+
+  def mainClasses( targetDirectory: File, classLoader : ClassLoader ): Seq[Class[_]] = {
+    val arrayClass = classOf[Array[String]]
+    val unitClass = classOf[Unit]
+
+    listFilesRecursive(targetDirectory)
+      .filter(_.isFile)
+      .map(_.getPath)
+      .collect{
+        // no $ to avoid inner classes
+        case path if !path.contains("$") && path.endsWith(".class") =>
+          classLoader.loadClass(
+            path
+              .stripSuffix(".class")
+              .stripPrefix(targetDirectory.getPath)
+              .stripPrefix(File.separator) // 1 for the slash
+              .replace(File.separator, ".")
+          )
+      }.filter(
+        _.getDeclaredMethods().exists( m =>
+          m.getName == "main"
+            && m.getParameterTypes.toList == List(arrayClass)
+            && m.getReturnType == unitClass
+        )
+      )
+  }
+
   implicit class ClassLoaderExtensions(classLoader: ClassLoader){
     def canLoad(className: String) = {
       try{
diff --git a/stage2/BasicBuild.scala b/stage2/BasicBuild.scala
index bcc3646..98deddc 100644
--- a/stage2/BasicBuild.scala
+++ b/stage2/BasicBuild.scala
@@ -136,8 +136,15 @@ trait BaseBuild extends DependencyImplementation with BuildInterface with Trigge
     )
   }
 
-  def runClass: String = "Main"
-  def run: ExitCode = lib.runMainIfFound( runClass, context.args, classLoader(context.classLoaderCache) )
+  
+  def mainClasses: Seq[Class[_]] = compile.toSeq.flatMap( lib.mainClasses( _, classLoader(classLoaderCache) ) )
+
+  def runClass: Option[String] = lib.runClass( mainClasses ).map( _.getName )
+
+  def run: ExitCode = runClass.map( lib.runMain( _, context.args, classLoader(context.classLoaderCache) ) ).getOrElse{
+    logger.task( "No main class found for " ++ projectDirectory.string )
+    ExitCode.Success
+  }
 
   def clean = {
     lib.clean(
diff --git a/stage2/Lib.scala b/stage2/Lib.scala
index 46fecf7..c18bf2e 100644
--- a/stage2/Lib.scala
+++ b/stage2/Lib.scala
@@ -201,7 +201,7 @@ final class Lib(logger: Logger) extends Stage1Lib(logger) with Scaffold{
 
   def consoleOrFail(msg: String) = {
     Option(System.console).getOrElse(
-      throw new Exception(msg + ". java.io.Console == null. See https://github.com/cvogt/cbt/issues/236")
+      throw new Exception(msg + ". System.console() == null. See https://github.com/cvogt/cbt/issues/236")
     )
   }
 
diff --git a/test/test.scala b/test/test.scala
index dfc35d0..8845528 100644
--- a/test/test.scala
+++ b/test/test.scala
@@ -1,4 +1,5 @@
-import cbt._
+package cbt
+package test
 import java.util.concurrent.ConcurrentHashMap
 import java.io.File
 import java.nio.file._