I'd like people with a good Cloudflare and Kotlin/JS understanding to review (or contribute to) my new project: https://github.com/StefanOltmann/cloudflare-steam-name-update-service I think a lot can be improved here. Especially how I pass in the environment - didn’t find a better way. And I don't like all the

js()

interop, too. I like this to be Kotlin/WASM, but the sample (a fork from the original hello world) I found was outdated and didn't work for me. So I appeciate if you drop me hints how to improve or helpful ressources (like sample code) how to properly work with Kotlin/JS (or even better Kotlin/WASM) on Cloudflare Workers. 🙂

As far as I recall, there was some talk about un-deprecating the

@EagerInitialization

annotation. If that is the case: 1. could it be also applicable to top-level functions? This would be useful for code that has to run when the JS module is initialized. The current workaround is a property that calls a function. 2. could we instead move to an annotation that starts with

@Js*

to streamline the naming? For example

@JsEager

or

@JsImmediate

.

Trying to upgrade Kotlin from 2.2.0 -> 2.2.10 and started getting this error:

Execution failed for task ':kotlinNpmInstall'.
>                 Process 'Resolving NPM dependencies using yarn' returns 1
                  Unknown Syntax Error: Unsupported option name ("--network-concurrency").

Any workaround?

What would be the correct way to add a dependency if the user has configured a specific feature? For example, I need a specific dependency if the user has defined

useCommonJs()

. To detect that, I'm using:

val moduleKind = project.objects.property<JsModuleKind>()
	project.tasks.withType<org.jetbrains.kotlin.gradle.targets.js.ir.KotlinJsIrLink> {
		moduleKind.set(compilerOptions.moduleKind)
	}

but by the time

moduleKind

is set, it's not allowed to add a

implementation(npm("foo", "1.0.0"))

anymore. I've also tried having a

: RequiresNpmDependencies

task with a dependency set that changes once

moduleKind

is known, and that works without the configuration cache, but with it I get a serialization crash within the configuration cache itself.

How can I achieve lazy loading to reduce initialize time of any kotlin js browser app?

Hello, I have a library that targets both Android and Js. It uses Metro for DI. I compile with

jsBrowserProductionLibraryDistribution

js {
        moduleName = project.name
        useEsModules()
        binaries.library()
    }

I have the following code

@Inject
internal class InvocationHandler(
    private val exposedFunctions: Map<String, Provider<ExposedFunction>>,
) {
    operator fun invoke(
        onInvocations: SharedFlow<Invocation>,
    ): Flow<Invocation> {
        return onInvocations
            .onEach {
                val exposedFunction = exposedFunctions[it.location] ?: return@onEach

                it.handle {
                    val fn = exposedFunction()
                    fn(it.parameters) // This throws an error on JS
                }
            }
    }
}

// ...

@Inject
@ContributesIntoMap(AppScope::class)
@ExposedAtLocation(ExposedFunctionLocation.IS_FILE_CACHED)
internal class IsFileCached(private val cacheRepository: CacheRepository) : ExposedFunction {
    override suspend fun invoke(args: List<Any>): Any {
        val fileUrl = args[0] as? String ?: return false
        return cacheRepository.isCached(fileUrl)
    }
}

For the code above, I will get

TypeError: fn is not a function

And if I print with

fn.toString

function (_this__u8e3s4, $completion) {
    return i.v8b(_this__u8e3s4, $completion);
  }

Do you know what could cause this issue?

I'm getting this weird import in the generated

kotlin-kotlin-stdlib.js

const DYNAMIC_MODULES_ID = '\0commonjs-dynamic-modules';
const HELPERS_ID = '\0commonjsHelpers.js';

Note the

\0

. Has anyone seen this before?

Im getting an error

Could not locate the bindings file

when I am installing

sqlite3

as a npm() dependnecy in build.gradle.kts:

implementation(npm("sqlite3",  "5.1.7"))

I think it has something to do with native bindings (C ?) . The library is this one Any pointers on how to use it in kotlin /js ?

running into

e: org.jetbrains.kotlin.util.FileAnalysisException: Somewhere in file /Users/casvanluijtelaar/Projects/***/deals/DealsOfferKey.kt: java.lang.NullPointerException: null cannot be cast to non-null type org.jetbrains.kotlin.fir.symbols.impl.FirRegularClassSymbol
	at org.jetbrains.kotlin.util.AnalysisExceptionsKt.wrapIntoFileAnalysisExceptionIfNeeded(AnalysisExceptions.kt:62)
	at org.jetbrains.kotlin.fir.FirCliExceptionHandler.handleExceptionOnFileAnalysis(Utils.kt:251)
	at org.jetbrains.kotlin.fir.resolve.transformers.FirSupertypeResolverTransformer.transformFile(FirSupertypesResolution.kt:892)
	at org.jetbrains.kotlin.fir.declarations.FirFile.transform(FirFile.kt:46)
	at org.jetbrains.kotlin.fir.resolve.transformers.FirTransformerBasedResolveProcessor.processFile(FirResolveProcessor.kt:48)
	at org.jetbrains.kotlin.fir.resolve.transformers.FirTotalResolveProcessor.process(FirTotalResolveProcessor.kt:36)
	at org.jetbrains.kotlin.fir.pipeline.AnalyseKt.runResolution(analyse.kt:24)
	at org.jetbrains.kotlin.fir.pipeline.FirUtilsKt.resolveAndCheckFir(firUtils.kt:76)

when I try to build

jsBrowserDevelopmentLibraryDistribution

seems to throw on any file with kotlinx-serializable imported. e.g. this file only contains:

import kotlinx.serialization.Serializable

@Serializable
data class DealsOfferKey(
    val offerId: Int,
    val offerInstanceUniqueId: String?,
)

removing the annotation and the import fixes the issue. but then errors on one of a million other files with serializable included. Anyone seen this before?

2.2.20 is out, and there are a lot of improvements for JS. https://github.com/JetBrains/kotlin/releases/tag/v2.2.20

Just an observation now that I've compiled with 2.2.20. The new

String.substring

approach is better because it directly calls JS'

substring

, however it now produces:

substring(response, startIndex, endIndex);

Where

substring

is:

function substring(_this__u8e3s4, startIndex, endIndex) {
  _init_properties_stringJs_kt__bg7zye();
  // Inline function 'kotlin.js.asDynamic' call
  return _this__u8e3s4.substring(startIndex, endIndex);
}

If instead you bring back

inline

for those two functions https://github.com/JetBrains/kotlin/blob/400e1ecadbef70744b6ee7eb6234a0a6ea8bbda8/libraries/stdlib/js/src/kotlin/text/stringJs.kt#L274-L276 you won't have to pass by the lazy initialization of the file-level properties. A similar situation is valid for

Long

too as far as I can see. Alternatively properties could be marked with

EagerInitialization

.

Is it possible to use

@JsName

on properties declared on a

@JsPlainObject

? I wanted to change some

snake_case

variables into

camelCase

, to make it look "better" in Kotlin I tried searching for it, but the only result of someone trying to do this was this conversation: https://kotlinlang.slack.com/archives/C0B8L3U69/p1728428182216839 However after testing it, it doesn't seem to work on Kotlin 2.2.0 😞

Are unsigned types fully supported on JS? I was trying to use them but I ran into a strange error:

fun main() {
    ubyteArrayOf(
        *listOf(ubyteArrayOf())[0]
    )
}

results in:

Unhandled JavaScript exception: listOf(...).get_c1px32_k$(...).slice is not a function

https://pl.kotl.in/nEyBqjkBZ The same code works just fine when replacing

ubyteArrayOf

with

byteArrayOf

or running it on JVM instead.

Worried about bundle size? Here are two options that can help decrease it: • Using ESM modules • Using ES2015 language features Both of these articles give examples of how the options affect the generated code.

Anybody else ran into this issue before? IDE isn’t able to resolve KotlinJsTargetDsl and it makes dev very annoying bc all the JsExport stuff shows red in the editor https://youtrack.jetbrains.com/issue/KT-81089/

Anyone else run into an issue where changing the version of an npm dependency (via the Gradle DSL, i.e.

implementation(npm(package, version))

does not invalidate build cache? Kotlin 2.2.0, Gradle 8.12 Running build before and after changing the NPM dependency shows the same build cache key for

compileKotlinJs

. I would expect this to trigger a failed build and prompt the user to run

kotlinUpgradeYarnLock

like normal.

While waiting for AWS SDK Multiplatform I wonder why there a no Kotlin-wrappers available for the official AWS S3 JS lib… isn’t that thing popular?

I'm writing type defs and came across

{GridCoordinates2D|HexagonalGridCube2D|Point} HexagonalGridCoordinates2D

and wondered, if there was a way to model that in Kotlin. Couldn't you use a marker interface for that? As in: an empty interface that all of these types extend?

Hello everybody, how can i instruct gradle to get a npm dependency directly from a github repo instead of npmjs.com?

How can I pass a parameter from the Gradle command line to my JS tests (Node, browser, Wasm)? Example: Indicate if tests run on CI.

Hi all, today I noticed that there are no null checks for non nullable fields for generated JS code in KMP. I was assuming that the behaviour might have been similar to JVM where generated bytecode has null checks and code fails fast but it is not. How do people overcome this usually ? I can manually add null checks in

init {}

block but not only kotlin gives warning for that, it's cumbersome process to add to all exposed classes and would pollute the code as well.

Just decided to open source this investment tracker I've been working on as a personal passion project: https://github.com/TENET-THEORY/knance. It is probably the only sample out there that shares code between ktor and next js. Inspired by https://github.com/Kotlin/kmp-fullstack-conference-cms. If you like it, give it a star!

[kotlin - Why can't I use @JsExport in commonMain? Workaround with expect/actual seems to work fine - Stack Overflow](https://stackoverflow.com/questions/79782181/why-cant-i-use-jsexport-in-commonmain-workaround-with-expect-actual-seems-to)

Good morning everyone ☀️ I need your input so much in the following question. In the thread, please share how you publish Kotlin/JS artifacts (not KLIB, but the executable) to a registry (e.g., NPM, JSR, Maven) and any pain points you've encountered with the approach. Thank you for the help 🙏 Artem, Kotlin/JS Lead

Kotlin 2.2.21-RC is out with a couple of fixes for K/JS. https://github.com/JetBrains/kotlin/releases/tag/v2.2.21-RC

[kotlin - Can we expose interfaces from

commonMain

to JS that can be implemented in Typescript? - Stack Overflow](https://stackoverflow.com/questions/79786639/can-we-expose-interfaces-from-commonmain-to-js-that-can-be-implemented-in-type)

How can you create Web Components using Kotlin/JS? I did try to follow this guide and, while it did work in the past, it seems that the

kotlin-browser

bindings for Web Components have changed quite a bit, and now I'm not able to get a custom element to work

Major bottleneck for me right now with kotlin/js is the compilation speed. It slows down the dev loop dramatically vs just using javascript. This is while building backends on nodejs Everything else is fantastic

Edit: https://kotlinlang.slack.com/archives/CDFP59223/p1759383119112699 What's up with this warning in 2.2.20? I suppose it's an IDE bug, and I don't have to worry about anything.

Is there a way for generated typescript files

d.ts

to have KDoc comments transferred over to

d.ts

from the Kotlin files?