feat: support lambdas that access variables outside the lambda

build-tools-gradle-test/build.gradle.kts

@@ -39,8 +39,9 @@ mpsBuild {
     }
 
     runMPS("runLambdaInMPS") {
+        val variableOutsideTheLambda = "a"
         implementation {
-            println("Lambda invoked")
+            println("Lambda invoked: $variableOutsideTheLambda")
         }
     }
 }

build-tools-gradle/src/main/kotlin/org/modelix/gradle/mpsbuild/InvokeLambda.kt

@@ -1,16 +1,17 @@
 package org.modelix.gradle.mpsbuild
 
+import java.io.FileInputStream
+import java.io.ObjectInputStream
+
 object InvokeLambda {
-    const val PROPERTY_KEY = "runMPS.lambda.name"
+    const val PROPERTY_KEY = "runMPS.lambda.file"
 
     @JvmStatic
     fun invoke() {
-        // System.getProperty(PROPERTY_KEY) would get instrumented which introduces a Gradle dependency
-        val lambdaName = System::class.java.getMethod("getProperty", String::class.java)
-            .invoke(null, PROPERTY_KEY) as String
-        val cls = Class.forName(lambdaName)
-        val lambdaInstance = cls.getField("INSTANCE").also { it.trySetAccessible() }
-            .get(null) as () -> Unit
+        val lambdaFileName = System.getProperty(PROPERTY_KEY)
+        val lambdaInstance = ObjectInputStream(FileInputStream(lambdaFileName)).use {
+            it.readObject() as () -> Unit
+        }
         lambdaInstance()
     }
 }

build-tools-gradle/src/main/kotlin/org/modelix/gradle/mpsbuild/MPSBuildPlugin.kt

@@ -43,6 +43,7 @@ import org.modelix.buildtools.runner.MPSRunner
 import org.modelix.buildtools.xmlToString
 import org.zeroturnaround.zip.ZipUtil
 import java.io.File
+import java.io.ObjectOutputStream
 import java.nio.file.Path
 import java.nio.file.Paths
 import java.text.SimpleDateFormat
@@ -411,14 +412,18 @@ class MPSBuildPlugin : Plugin<Project> {
                 val exportImplTask: TaskProvider<Task>? = if (mainMethodImpl != null) {
                     val implJarFile = workDir.resolve(entry.key + "-impl.jar")
                     val implClass = mainMethodImpl::class.java
+                    val serializedLambdaFile = workDir.resolve(entry.key + "-impl.obj")
                     runnerConfig = runnerConfig.copy(
                         classPathElements = runnerConfig.classPathElements + implJarFile,
                         mainClassName = InvokeLambda::class.java.name,
                         mainMethodName = InvokeLambda::invoke.name,
-                        jvmArgs = runnerConfig.jvmArgs + "-D${InvokeLambda.PROPERTY_KEY}=${implClass.name}"
+                        jvmArgs = runnerConfig.jvmArgs + "-D${InvokeLambda.PROPERTY_KEY}=${serializedLambdaFile.absolutePath}"
                     )
                     project.tasks.register(entry.key + "_exportImpl") {
                         doLast {
+                            ObjectOutputStream(serializedLambdaFile.outputStream()).use {
+                                it.writeObject(mainMethodImpl)
+                            }
                             ZipOutputStream(implJarFile.outputStream()).use { zos ->
                                 for (cls in listOf(implClass, InvokeLambda::class.java)) {
                                     zos.putNextEntry(ZipEntry(cls.getResourceName().trimStart('/')))
@@ -704,9 +709,17 @@ class MPSBuildPlugin : Plugin<Project> {
 private fun String.firstLetterUppercase() = if (isEmpty()) this else substring(0, 1).toUpperCase() + drop(1)
 
 private fun Class<*>.readClassBytes(): ByteArray {
+    // Try to get the non-instrumented original class file first
+    val classLoaders = generateSequence(classLoader) { it.parent }
+    for (currentLoader in classLoaders.toList().asReversed()) {
+        val resource = currentLoader.getResource(getResourceName()) ?: continue
+        return resource.readBytes()
+    }
+
     val resource = getResource(getResourceName())
         ?: throw RuntimeException("Resource ${getResourceName()} not found in $classLoader")
     return resource.readBytes()
+
 }
 
 private fun Class<*>.getResourceName() = "/${name.replace(".", "/")}.class"