flonso/kotlin-scala.js

Compile Kotlin code to JavaScript through the Scala.js compiler

Kotlin-Scala.js

Compile Kotlin code to JavaScript through the Scala.js compiler

Documentation

A full technical report is available under the docs/report directory. Useful resources include the Kotlin Documentation and the Scala.js Website.

Running the compiler

sbt "run {list_of_source_files} -d {output_sjsir_dir} -kotlin-home {kotlin_home_directory}"

To compile the Kotlin Standard Library use the -Xallow-kotlin-package option to ignore the package kotlin reservation.

• A gradle plugin is also available with an example project here
• A basic maven plugin is available here

Testing

All tests are stored under src/test and can be run with sbt test. Before running them, create the folders src/test/resources/out and src/test/resources/benchmark_out.

You will need to install the same version of Kotlin which is used by SBT.

To do so, either install it from here https://kotlinlang.org/docs/tutorials/command-line.html and/or change the path to the directory by changing the KOTLIN_HOME value in BlackBoxTest.scala

The tests require the presence of the Scala.js library jar file inside src/test/resources/lib. It should be included in this repository. If you need to change the Scala.js version in use for the tests, be sure to change the referenced .jar inside the BlackBoxTest.scala file.

Kotlin Standard Library

A test has been setup to check that the IR generated for the files constituting the Kotlin Standard Library is valid. Because the standard library is not compilable yet, the test has been disabled by default. It can be enabled in file src/test/scala/KotlinStdLibTest.

Benchmarking

Benchmarks are available in src/test/scala/BenchmarkTest. Outputs are written to the benchmark_out directory mentioned above.

kotlin-scala.js's Issues

Behaviour of is operator on Int and Double

The following Kotlin code doesn't produce the same output on both Kotlin "stock" compiler and the Kotlin-Scala.js compiler :

fun main(args: Array<String>) {
    val myDouble = 1.7

    check(myDouble)
}

fun check(a: Any) {

    if (a is Int) println("$a is an Int")
    if (a is Double) println("$a is a Double")
    if (a is Long) println("$a is a Long")


    if (a !is Int) println("$a is not an Int")
    if (a !is Double) println("$a is not a Double")
    if (a !is Long) println("$a is not a Long")
}

Output for KotlinJS compiler :

1.7 is an Int
1.7 is a Double
1.7 is not a Long

Output for Kotlin-Scala.js compiler :

1.7 is a Double
1.7 is not an Int
1.7 is not a Long

Need to investigate the reason behind this difference.