Load main-kts jar automatically from scripting plugin, if available

compiler/testData/integration/ant/js/verbose/build.log.expected

@@ -4,6 +4,7 @@ Buildfile: [TestData]/build.xml
 build:
 [kotlin2js] Compiling [[TestData]/root1] => [[Temp]/out.js]
 [kotlin2js] logging: using Kotlin home directory [KotlinProjectHome]/dist/kotlinc
+[kotlin2js] logging: configure scripting: Added template org.jetbrains.kotlin.mainKts.MainKtsScript from [[CompilerLib]/kotlin-main-kts.jar, [CompilerLib]/kotlin-reflect.jar, [CompilerLib]/kotlin-script-runtime.jar, [CompilerLib]/kotlin-stdlib.jar]
 [kotlin2js] logging: compiling source files: [TestData]/root1/foo.kt
 
 BUILD SUCCESSFUL

compiler/testData/integration/ant/jvm/verbose/build.log.expected

@@ -5,6 +5,7 @@ build:
   [kotlinc] Compiling [[TestData]/hello.kt] => [[Temp]/hello.jar]
   [kotlinc] logging: using Kotlin home directory [KotlinProjectHome]/dist/kotlinc
   [kotlinc] logging: configuring the compilation environment
+  [kotlinc] logging: configure scripting: Added template org.jetbrains.kotlin.mainKts.MainKtsScript from [[CompilerLib]/kotlin-main-kts.jar, [CompilerLib]/kotlin-reflect.jar, [CompilerLib]/kotlin-script-runtime.jar, [CompilerLib]/kotlin-stdlib.jar]
 
 BUILD SUCCESSFUL
 Total time: [time]

plugins/scripting/scripting-compiler-impl/src/org/jetbrains/kotlin/scripting/definitions/AutoloadedScriptDefinitions.kt

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.scripting.definitions
+
+import java.io.File
+import kotlin.script.experimental.host.ScriptingHostConfiguration
+import kotlin.script.experimental.jvm.impl.tryGetResourcePathForClass
+import kotlin.script.experimental.jvm.util.matchMaybeVersionedFile
+
+class AutoloadedScriptDefinitions(
+    private val hostConfiguration: ScriptingHostConfiguration,
+    private val baseClassloader: ClassLoader,
+    private val messageReporter: MessageReporter
+) : ScriptDefinitionsSource {
+
+    private val basePath by lazy(LazyThreadSafetyMode.PUBLICATION) {
+        tryGetResourcePathForClass(AutoloadedScriptDefinitions::class.java)?.parentFile?.takeIf { it.isDirectory } ?: File(".")
+    }
+
+    override val definitions: Sequence<ScriptDefinition> = sequence {
+        val mainKtsJars = basePath.listFiles { f: File ->
+            MAIN_KTS_JARS.any { expected ->
+                f.matchMaybeVersionedFile(expected) && f.extension == "jar"
+            }
+        }?.toList()
+        if (mainKtsJars != null && mainKtsJars.size >= MAIN_KTS_JARS.size) {
+            yieldAll(
+                loadScriptTemplatesFromClasspath(
+                    listOf("org.jetbrains.kotlin.mainKts.MainKtsScript"),
+                    mainKtsJars,
+                    emptyList(),
+                    baseClassloader,
+                    hostConfiguration,
+                    messageReporter
+                )
+            )
+        }
+    }
+
+    companion object {
+        private val MAIN_KTS_JARS = listOf("kotlin-main-kts", "kotlin-stdlib", "kotlin-script-runtime", "kotlin-reflect")
+    }
+}

plugins/scripting/scripting-compiler-impl/src/org/jetbrains/kotlin/scripting/definitions/ScriptiDefinitionsFromClasspathDiscoverySource.kt

@@ -311,7 +311,7 @@ private fun loadScriptDefinition(
         if (def != null) {
             messageReporter(
                 ScriptDiagnostic.Severity.DEBUG,
-                "Configure scripting: Added template $templateClassName from ${classpathWithLoader.classpath}"
+                "Configure scripting: Added template $templateClassName from ${classpathWithLoader.classpath.sorted()}"
             )
             return def
         }

plugins/scripting/scripting-compiler/src/org/jetbrains/kotlin/scripting/compiler/plugin/ScriptingCompilerConfigurationExtension.kt

@@ -18,10 +18,7 @@ import org.jetbrains.kotlin.idea.KotlinFileType
 import org.jetbrains.kotlin.scripting.compiler.plugin.definitions.CliScriptDefinitionProvider
 import org.jetbrains.kotlin.scripting.compiler.plugin.impl.reporter
 import org.jetbrains.kotlin.scripting.configuration.ScriptingConfigurationKeys
-import org.jetbrains.kotlin.scripting.definitions.ScriptDefinition
-import org.jetbrains.kotlin.scripting.definitions.ScriptDefinitionProvider
-import org.jetbrains.kotlin.scripting.definitions.ScriptDefinitionsFromClasspathDiscoverySource
-import org.jetbrains.kotlin.scripting.definitions.getEnvironment
+import org.jetbrains.kotlin.scripting.definitions.*
 import java.io.File
 import kotlin.script.experimental.host.ScriptingHostConfiguration
 
@@ -70,12 +67,15 @@ class ScriptingCompilerConfigurationExtension(
                 )
             }
 
-            configuration.add(
+            configuration.addAll(
                 ScriptingConfigurationKeys.SCRIPT_DEFINITIONS_SOURCES,
-                ScriptDefinitionsFromClasspathDiscoverySource(
-                    configuration.jvmClasspathRoots,
-                    hostConfiguration,
-                    messageCollector.reporter
+                listOf(
+                    ScriptDefinitionsFromClasspathDiscoverySource(
+                        configuration.jvmClasspathRoots,
+                        hostConfiguration,
+                        messageCollector.reporter
+                    ),
+                    AutoloadedScriptDefinitions(hostConfiguration, this::class.java.classLoader, messageCollector.reporter)
                 )
             )