Trying to run Kotlin script in IntelliJ IDEA

Question

I am learning Kotlin by doing Kotlin Koans int IntelliJ EduKotlin plugin (https://plugins.jetbrains.com/plugin/8186). While doing tasks and running them im this plugin is working, I am not able to create new Kotlin script and run it without this plugin.

Sample code in a file named Hello.kt:

fun hello() : String {
    return "ok"
}

Then I create new run configuration derived from 'Kotlin script', set 'Working directory' to ProjectName/src folder (or ProjectName folder, same result) and IDE shows me a 'Could not find script file: Hello.kt' warning as in the screen below:

And indeed, while trying to run script I got following stacktrace:

"C:\Program Files\Java\jdk1.8.0_74\bin\java" -Dfile.encoding=windows-1250 -classpath C:\Users\myUser\.IdeaIC2016\config\plugins\Kotlin\kotlinc\lib\kotlin-compiler.jar;C:\Users\myUser\.IdeaIC2016\config\plugins\Kotlin\kotlinc\lib\kotlin-reflect.jar;C:\Users\myUser\.IdeaIC2016\config\plugins\Kotlin\kotlinc\lib\kotlin-runtime.jar org.jetbrains.kotlin.cli.jvm.K2JVMCompiler -script Hello.kt
exception: java.lang.RuntimeException: Failed to evaluate script: kotlin.KotlinNullPointerException
at org.jetbrains.kotlin.cli.jvm.compiler.KotlinToJVMBytecodeCompiler.compileScript(KotlinToJVMBytecodeCompiler.kt:263)
at org.jetbrains.kotlin.cli.jvm.compiler.KotlinToJVMBytecodeCompiler.compileAndExecuteScript(KotlinToJVMBytecodeCompiler.kt:212)
at org.jetbrains.kotlin.cli.jvm.K2JVMCompiler.doExecute(K2JVMCompiler.kt:181)
at org.jetbrains.kotlin.cli.jvm.K2JVMCompiler.doExecute(K2JVMCompiler.kt:49)
at org.jetbrains.kotlin.cli.common.CLICompiler.exec(CLICompiler.java:181)
at org.jetbrains.kotlin.cli.common.CLICompiler.exec(CLICompiler.java:138)
at org.jetbrains.kotlin.cli.common.CLICompiler.exec(CLICompiler.java:57)
at org.jetbrains.kotlin.cli.common.CLICompiler.doMainNoExit(CLICompiler.java:248)
at org.jetbrains.kotlin.cli.common.CLICompiler.doMain(CLICompiler.java:238)
at org.jetbrains.kotlin.cli.jvm.K2JVMCompiler$Companion.main(K2JVMCompiler.kt:248)
at org.jetbrains.kotlin.cli.jvm.K2JVMCompiler.main(K2JVMCompiler.kt)
Caused by: kotlin.KotlinNullPointerException
at org.jetbrains.kotlin.cli.jvm.compiler.KotlinToJVMBytecodeCompiler.compileScript(KotlinToJVMBytecodeCompiler.kt:475)
... 10 more


Process finished with exit code 2

What more, the hello method is marked as never used. However, when I change file extension from .kt to .ktscript, then this method is marked as used, and the output from running code is following:

"C:\Program Files\Java\jdk1.8.0_74\bin\java" -Dfile.encoding=windows-1250 -classpath C:\Users\myUser\.IdeaIC2016\config\plugins\Kotlin\kotlinc\lib\kotlin-compiler.jar;C:\Users\myUser\.IdeaIC2016\config\plugins\Kotlin\kotlinc\lib\kotlin-reflect.jar;C:\Users\myUser\.IdeaIC2016\config\plugins\Kotlin\kotlinc\lib\kotlin-runtime.jar org.jetbrains.kotlin.cli.jvm.K2JVMCompiler -script Hello.kt

error: source file or directory not found: Hello.kt

Process finished with exit code 1

So my question is: what am I missing when trying to create and run Kotlin code in a standalone Kotlin script in IntelliJ?

Answer 1

A standalone Kotlin script file needs to have a .kts extension. If you rename your file, you also need to make sure that your run configuration is updated to refer to the new name of the file.

Also, if you create any file (a regular Kotlin file or a .kts file) which only contains a function, running the script will not produce any output, because the function will not be called. To see some output, you need to call the function in your script:

fun hello(): String {
    return "ok"
}

println(hello())

The stacktrace that you saw is a bug in Kotlin.