Script with a main method is not run in kscript

[xgouchet]

I'm using IntelliJ to write kotlin script. In order to make my script valid with IntelliJ inspections, I'm defining a standard main method. The problem is that when running my file from kscript, my main method is not run at all.

Is there a special action to run the main method from the command line ?

[holgerbrandl]

Not sure if I'm missing your point here, but there is no need for a main method in a kotlin kts script. See https://kotlinlang.org/docs/tutorials/command-line.html#using-the-command-line-to-run-scripts

I could imagine that you're trying to provide a regular kotlin class file (which indeed would need a main method as entry point) to kscript. However Kotlin kts scripts allow for more simplistic code. E.g.

print(1+1)

is a valid kotlin script.

Regular class files are not supported (yet) by kscript. It crossed my mind to do so, but it is conceptually not possible without making assumptions about the user code, since a kt file could contain multiple classes with a main methods, so the entry point might not be always clearly defined.

I hope this answers your question.

Inspections work fine without. If not it's most likely an IJ bug.

I'll update docs to point out the difference between scripts and regular kotlin classes sources more clear.

[holgerbrandl]

One potential fix would be via another configuration comment, similar to //DEPS. E.g.

//ENTRY Foo.main

could be implemented to instruct kscript to use the companion method main of the class Foo as entrypoint. Technically it would do so by adding the line

Foo.main(args)

to the end of the provided user code to launch the application. So we would implicitly treat kotlin kt files as kts files. I think it is legit to do so, but I'm not really sure.

I'm also unsure if such a feature would be conceptually too confusing. Furthermore, such a solution would still require some effort from the user to define //ENTRY.
One the plus side, it would extend kscript to also become a more generic application launcher.

Your opinions are welcome here!

[xgouchet]

Thanks a lot for all these precisions.

To explain my issue with IntelliJ, let's use the following script example :

    #!/usr/bin/env kscript
    
    println("Hello from Kotlin!")
    for (arg in args) {
        println("arg: $arg")
    }

Even if the file has a .kts extension, IntelliJ complains that the args reference is undefined. This means that writing kscript with all the power of IJ is not possible.

[xgouchet]

Regarding your //ENTRY directive, this would indeed be a good thing to specify, but you could use the default main function (if any), eg :

#!/usr/bin/env kscript

fun main(args: Array<String>) {
    args.forEach { it -> println(it) }
}

[holgerbrandl]

Concerning your first comment. This is a known regression In IJ since kotlin v1.1, which is indeed super-annoying. Please vote for it under https://youtrack.jetbrains.com/issue/KT-16802

[holgerbrandl]

Concerning the //ENTRY directive. Assuming the presence of a main method does not make sense imho because kotlin scripts don't require a main and work fine without.

And since Kotlin is very flexible concerning how main can be defined in a kt source file, I'm not sure it's intuitive to assume one particular type of main. E.g. another popular to define via a companion method:

class Foo{
    companion object {
        @JvmStatic fun main(args: Array<String>) {
            println("Hello World")
        }
    }
}

To detect the entry-point programmatically here would require quite some non-trivial logic.

[holgerbrandl]

I finally managed to implement it for kt files (because its the only context in which an entry-point declaration makes sense imho).

See here for an example about how to use the new //ENTRY directive.

Please have a look and let me know what you think about it.

[fjay]

The main method is still not available with the latest version 1.6.0

kscript K2.kt
K2.kt:10:20: warning: parameter 'name' is never used
fun findUserByName(name: String): User = null!!
^
.Foor: could not find or load main class test

[holgerbrandl]

Thanks for the feedback. Could you run

kscript --clear-cache
kscript --version

first to make sure that you're running the latest version and caching is not causing the error.

Btw the user warning is normal, as the argument name is indeed not used. I'll update the example.

Do you use the provided example? If not, could you attach your K2.kt to this ticket?

[fjay]

I've run
kscript --clear-cache
kscript --version

I'm sure it's in v1.6.0, and it doesn't work for me.

The content of K2.kt is what you provided before

Here is the jar file after the execution