1 files changed, 66 insertions, 0 deletions
diff --git a/main/core/src/mill/util/ClassLoader.scala b/main/core/src/mill/util/ClassLoader.scala
new file mode 100644
index 00000000..c0421a7b
--- /dev/null
+++ b/main/core/src/mill/util/ClassLoader.scala
@@ -0,0 +1,66 @@
+package mill.util
+
+import java.net.{URL, URLClassLoader}
+
+import ammonite.ops._
+import io.github.retronym.java9rtexport.Export
+
+object ClassLoader {
+
+  def create(urls: Seq[URL], parent: java.lang.ClassLoader)(
+      implicit ctx: Ctx.Home): URLClassLoader = {
+    new URLClassLoader(
+      makeUrls(urls).toArray,
+      refinePlatformParent(parent)
+    ) {
+      override def findClass(name: String): Class[_] = {
+        if (name.startsWith("com.sun.jna")) getClass.getClassLoader.loadClass(name)
+        else super.findClass(name)
+      }
+    }
+  }
+
+  def create(urls: Seq[URL],
+             parent: java.lang.ClassLoader,
+             customFindClass: String => Option[Class[_]])(
+      implicit ctx: Ctx.Home): URLClassLoader = {
+    new URLClassLoader(
+      makeUrls(urls).toArray,
+      refinePlatformParent(parent)
+    ) {
+      override def findClass(name: String): Class[_] = {
+        if (name.startsWith("com.sun.jna")) getClass.getClassLoader.loadClass(name)
+        else customFindClass(name).getOrElse(super.findClass(name))
+      }
+    }
+  }
+
+  /**
+    *  Return `ClassLoader.getPlatformClassLoader` for java 9 and above, if parent class loader is null,
+    *  otherwise return same parent class loader.
+    *  More details: https://docs.oracle.com/javase/9/migrate/toc.htm#JSMIG-GUID-A868D0B9-026F-4D46-B979-901834343F9E
+    *
+    *  `ClassLoader.getPlatformClassLoader` call is implemented via runtime reflection, cause otherwise
+    *  mill could be compiled only with jdk 9 or above. We don't want to introduce this restriction now.
+    */
+  private def refinePlatformParent(parent: java.lang.ClassLoader): ClassLoader = {
+    if (ammonite.util.Util.java9OrAbove) {
+      if (parent == null)
+        classOf[ClassLoader]
+          .getMethod("getPlatformClassLoader")
+          .invoke(null)
+          .asInstanceOf[ClassLoader]
+      else parent
+    } else {
+      parent
+    }
+  }
+
+  private def makeUrls(urls: Seq[URL])(implicit ctx: Ctx.Home): Seq[URL] = {
+    if (ammonite.util.Util.java9OrAbove) {
+      urls :+ Export.rtAt(ctx.home.toIO).toURI.toURL
+    } else {
+      urls
+    }
+  }
+}