Run Main.main in current process (#115)

* no message

* fix compile

* fix compile again

* finishing in process running

* remove comment

* fix bug

* fix bug

1 files changed, 57 insertions, 0 deletions

diff --git a/core/src/main/scala/mill/modules/Jvm.scala b/core/src/main/scala/mill/modules/Jvm.scala
index 48f100b2..888a687b 100644
--- a/core/src/main/scala/mill/modules/Jvm.scala
+++ b/core/src/main/scala/mill/modules/Jvm.scala
@@ -1,6 +1,7 @@
 package mill.modules
 
 import java.io.FileOutputStream
+import java.lang.reflect.Modifier
 import java.net.URLClassLoader
 import java.nio.file.attribute.PosixFilePermission
 import java.util.jar.{JarEntry, JarFile, JarOutputStream}
@@ -9,6 +10,7 @@ import ammonite.ops._
 import mill.define.Task
 import mill.eval.PathRef
 import mill.util.Ctx
+import mill.util.Ctx.LogCtx
 import mill.util.Loose.Agg
 
 import scala.annotation.tailrec
@@ -36,6 +38,61 @@ object Jvm {
     %("java", "-cp", classPath.mkString(":"), mainClass, options)
   }
 
+  def inprocess(mainClass: String,
+    classPath: Agg[Path],
+    options: Seq[String] = Seq.empty)
+    (implicit ctx: Ctx): Unit = {
+    inprocess(classPath, classLoaderOverrideSbtTesting = false, cl => {
+      getMainMethod(mainClass, cl).invoke(null, options.toArray)
+    })
+  }
+
+  private def getMainMethod(mainClassName: String, cl: ClassLoader) = {
+    val mainClass = cl.loadClass(mainClassName)
+    val method = mainClass.getMethod("main", classOf[Array[String]])
+    // jvm allows the actual main class to be non-public and to run a method in the non-public class,
+    //  we need to make it accessible
+    method.setAccessible(true)
+    val modifiers = method.getModifiers
+    if (!Modifier.isPublic(modifiers))
+      throw new NoSuchMethodException(mainClassName + ".main is not public")
+    if (!Modifier.isStatic(modifiers))
+      throw new NoSuchMethodException(mainClassName + ".main is not static")
+    method
+  }
+
+
+  def inprocess[T](classPath: Agg[Path],
+    classLoaderOverrideSbtTesting: Boolean,
+    body: ClassLoader => T): T = {
+    val cl = if (classLoaderOverrideSbtTesting) {
+      val outerClassLoader = getClass.getClassLoader
+      new URLClassLoader(
+        classPath.map(_.toIO.toURI.toURL).toArray,
+        ClassLoader.getSystemClassLoader().getParent()){
+        override def findClass(name: String) = {
+          if (name.startsWith("sbt.testing.")){
+            outerClassLoader.loadClass(name)
+          }else{
+            super.findClass(name)
+          }
+        }
+      }
+    } else {
+      new URLClassLoader(
+        classPath.map(_.toIO.toURI.toURL).toArray,
+        ClassLoader.getSystemClassLoader().getParent())
+    }
+    val oldCl = Thread.currentThread().getContextClassLoader
+    Thread.currentThread().setContextClassLoader(cl)
+    try {
+      body(cl)
+    }finally{
+      Thread.currentThread().setContextClassLoader(oldCl)
+      cl.close()
+    }
+  }
+
   def subprocess(mainClass: String,
                  classPath: Agg[Path],
                  jvmOptions: Seq[String] = Seq.empty,