kotlinlang #webassembly

I want to display different parts of the wasm bundle on different pages. It seems the most straighforward way is to pass parameters to the entry point in js and then parse the params in kotlin

Jaypalsinh Barad

06/24/2025, 10:01 AM

is there any way to remove #
from compose navigation?

base_url/#route_name

base_url/route_name

martmists

06/24/2025, 5:20 PM

How would I create a module definition jszip? it has a

namespace JSZip

with

new(): this;

and

(): JSZip

but I can't figure out how to call it. I tried

external fun JSZip

as well as

external class JSZip

and both give errors.

Anuta Vlad Sv

06/26/2025, 9:18 AM

Hi! I was wondering if this issue was fixed in kotlin 2.2.0 https://youtrack.jetbrains.com/issue/KT-68533/Kotlin-2.0-WasmJs-error-when-using-RepositoriesMode.FAILONPROJECTREPOS

chrisjenx

06/27/2025, 6:18 PM

Super bummed, got the whole project ready for wasm support, finally fixed up all expect/actuals and errors. now seeing a IR error 😞

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e: java.lang.IllegalStateException: Parent of element (VALUE_PARAMETER kind:Regular name:$composer index:0 type:androidx.compose.runtime.Composer? [assignable]) is not initialized.
Please assign it explicitly or use utility such as IrElement.patchDeclarationParents().
        at org.jetbrains.kotlin.ir.declarations.IrDeclarationBase.getParent(IrDeclarationBase.kt:22)

I'll create a ticket, but can't share this project, dunno if anyone can help where the issue might be based on the error?

Phil Burk

06/28/2025, 1:09 AM

I am trying to call some audio rendering code in Kotlin from a WebAudio AudioWorkletProcessor in JavaScript. I tried this: https://kotlinlang.org/docs/wasm-js-interop.html#functions-with-the-jsexport-annotation

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//import exports from "./module.mjs"
import exports from "./composeApp.js"
console.log("Kotlin random code is " + exports.renderKotlinAudio());

But I always get: SyntaxError: Unexpected identifier 'exports' I am using Kotlin/Compose multi-platform code. My Kotlin WASM code has:

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@OptIn(ExperimentalJsExport::class)
@JsExport
fun renderKotlinAudio(): Float {
    return Random.nextFloat()
}

I spent a lot of time with Gemini giving me increasingly complex solutions that did not work. Has anyone actually done this successfully?

Charlie Tapping

06/28/2025, 2:41 PM

Chasm now supports producer modules in

0.1.1

of its Gradle plugin. This is really exploratory work but ultimately the idea behind producer modules is to have an experience wherefore you write a module of code in Kotlin like you would any other, it has a well defined pure Kotlin interface which other modules can depend upon, but this module has the potential to be interpreted with all the benefits that come with that I’ve updated the documentation, and added a producer module to the example project for you to see it in action. Do let me know what you think, any feedback is more than welcome ✌️

てべすてん- TBSten -

06/29/2025, 1:17 AM

Someone help me! I am trying to add WasmJS support to Tart, a Flux architecture library. I simply added

kotlin.wasmJs.browser()

and

kotlin.wasmJs.nodejs()

to the module. However, when I run the

./gradlew wasmJsBrowserTest

task for testing, I get the error: command

/home/runner/.gradle/nodejs/node-v22.0.0-linux-x64/bin/node' exited with errors (exit code: 1)

(this occurs both in CI and locally). The ./gradlew jsBrowserTest task succeeds, so this is puzzling. • CI Error Log: ◦ wasmJsBrowserTest: https://github.com/yumemi-inc/Tart/actions/runs/15945080589/job/44978107464?pr=129#step:6:221 ◦ jsBrowserTest: https://github.com/yumemi-inc/Tart/actions/runs/15384920112/job/43281638863?pr=125 • Source code: https://github.com/TBSten/Tart/tree/feature/wasm ◦ You can verify this locally in

git clone <https://github.com/TBSten/Tart> && git fetch origin feature/wasm && git checkout feature/wasm

. As shown in the CI Error Log > jsBrowserTest, no explicit browser setup is performed in the CI environment, but the

jsBrowserTest

task has been successful in the past. I expected wasmJs to work similarly, but it does not, which is puzzling.

Anuta Vlad Sv

07/01/2025, 7:41 AM

Hello! While exploring the "What's New in Kotlin 2.2.0" section related to Kotlin/Wasm, I came across this example: kotlin

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@JsExport
expect class WindowManager {
    fun close()
}

// jsMain

@JsExport
actual class WindowManager {
    fun close() {
        window.close()
    }
}

Up until now, I could only use the @JsExport annotation on functions. When I tried applying it to a class, I got the error: "This annotation is not applicable to target 'class'. Applicable targets: function." Is this a documentation error, or is @JsExport now intended to work with classes as well?

Vladyslav

07/01/2025, 11:09 AM

Hi there , is that possible to somehow compile kotlin code into wasm32-unknown-unknow target , make it like lib with no entry point ?

Robert Jaros

07/01/2025, 1:33 PM

When running Kotlin/WasmJS app in Firefox 140 I see this warning in the browser console:

The WebAssembly exception handling 'try' instruction is deprecated and should no longer be used. Please recompile to use the 'try_table' instruction instead.

. Is this a known issue?

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Charlie Tapping

07/01/2025, 6:59 PM

I’ve noticed the compiler always generates an _initialize function, irrespective as to whether the program needs it. Is there any work to conditionally include this function if its needed? It looks like the function does a bunch of different things but could it also be set as a start function if its idempotent? I guess this is a question for @bashor @Artem Kobzar

chrisjenx

07/03/2025, 5:43 PM

I have multiple projects now, anything beyond a basic templete generated by the KMP plugin either doens't compile or we get runtime errors:

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[object WebAssembly.Exception]
    at handleError (webpack-internal:///../../node_modules/webpack-dev-server/client/overlay.js:251:58)
    at eval (webpack-internal:///../../node_modules/webpack-dev-server/client/overlay.js:274:7)

(When other targets work fine)

darkmoon_uk

07/08/2025, 10:57 PM

⚠️ Does Kotlin (WASM/JS) have a value class equality problem? For an App with a financial component, I'm creating a

Decimal

abstraction over: • JVM/Android (

BigDecimal

) ✅ • iOS (

NSDecimalNumber

) ✅ • ...and finally WasmJs (npm's

decimal.js

) ⚠️ In such situations, for the sake of resource efficiency, we would like to use a

value class

to unify these. This is almost working fine - perfectly with JVM/iOS - but theres a problem with equality when it comes to the wasmJs target. Unless I'm mistaken, it works like this:

value class

equality defers to the

equals(other: Any?)

of the wrapped value. ...which for JVM and iOS, is already mapped (as a matter of built-in KMP Interop.) to the canonical function of each platform; being JVM equals and iOS isEqual. With wasmJs (and JS in general I guess?) there is no canonical equality function, which entails that common code

equals

can currently only ever compare object identity for WASM/JS value classes ❓ Current 'KMP + value class' design leaves us with no opportunity to defer to a suitable equivalence function (like the

equals

function provided by decimal.js). This breaks use cases for naturally equatable objects. This means the

value class

efficiency dream is off the table ⁉️ Since we can't currently intercept

equals

by either: • Overriding

equals

in a

value class

(compiler error) 🙅 • Nor at the level of declaring an

external class

for JS mapping (an affordance here could be nice) 🙅 (

JsAny

Any

issue) Are there any workarounds? While this may not be a bug in KMP JS/WASM target; it appears to be a significant '_feature usability issue_' for such cases.

Thierry Kh

07/17/2025, 11:21 PM

Hi. I have been focusing on the Android target of my project these past weeks, and updated some dependencies (Kotlin 2.2.0, Compose 1.9.0-alpha03, lifecycle-runtime-compose 2.9.1, Koin 4.1.0, Adaptive 1.2.0-alpha03). Now that i try to run the Wasm target, i get this error :

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[object WebAssembly.Exception]
    at handleError (<webpack://composeApp/../../node_modules/webpack-dev-server/client/overlay.js?:251:58|webpack://composeApp/../../node_modules/webpack-dev-server/client/overlay.js?:251:58>)
    at eval (<webpack://composeApp/../../node_modules/webpack-dev-server/client/overlay.js?:274:7|webpack://composeApp/../../node_modules/webpack-dev-server/client/overlay.js?:274:7>)

I have no idea about what causes this so far. The Android, JVM and JS apps work. I also use Voyager 1.1.0-beta03 and Multiplatform Settings 1.3.0. It used to run fine on Kotlin 2.1.20, Compose 1.8.1, lifecycle-runtime-compose 2.9.0-alpha05 and Koin 4.0.2-RC3.

John O'Reilly

07/18/2025, 7:54 PM

Upgraded project here to Kotlin 2.2.20-Beta1 and getting following when running Compose for Web app.....all other targets seem ok

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WebAssembly.instantiate(): Import #5281 "./skiko.mjs" "org_jetbrains_skia_Shader__1nMakeWithLocalMatrix": function import requires a callable
LinkError: WebAssembly.instantiate(): Import #5281 "./skiko.mjs" "org_jetbrains_skia_Shader__1nMakeWithLocalMatrix": function import requires a callable

Winson Chiu

07/19/2025, 7:08 PM

Does anyone know how to configure

-Xwasm-use-new-exception-proposal

only for

wasmJsDevelopmentRun

and not

wasmJsBrowserDistribution

? I've been adding the flag manually when running the former, but curious if it can be automated, because sometimes I forget and waste a build. 😐

chrisjenx

07/23/2025, 4:16 PM

Is there an "official" way to have production/development env/distribution? seems like there is no way to pick development/production compilation/distribution targets? This seems not like the best/but only way... https://gist.github.com/CameronProbert/85b7d60fa9572d93566f5c5ee62441e0

Tóth István Zoltán

07/23/2025, 6:24 PM

When porting JS code to WebAssembly, what strategy should I follow for functions not exposed by kotlinx.browser? For example, this works for JS but I can't figure out how to do this in WASM.

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private suspend fun Blob.asByteArray(): ByteArray {
        //<https://developer.mozilla.org/en-US/docs/Web/API/Blob/arrayBuffer>
        val buffer = asDynamic().arrayBuffer() as Promise<ArrayBuffer>
        return Int8Array(buffer.await()).unsafeCast<ByteArray>()
    }

Kinar Sharma

07/24/2025, 12:09 PM

Hi guys, I was configuring my compose multiplatform app for WasmJS to run it on web, I'm able to make it run but as soon as it launches I get an error screen with the following error, and I'm not able to figure out the issue with this message, can anyone help me in resolving or get more detailed logs to resolve this issue

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WebAssembly.instantiateStreaming(): Compiling function #80262:"in.porter.owner.ownerapp.shared.core.journeys.r..." failed: struct.set[1] expected type (ref null 13693), found struct.get of type (ref null 431) @+13386268
CompileError: WebAssembly.instantiateStreaming(): Compiling function #80262:"in.porter.owner.ownerapp.shared.core.journeys.r..." failed: struct.set[1] expected type (ref null 13693), found struct.get of type (ref null 431) @+13386268

sns

07/24/2025, 11:17 PM

Hi, does anyone know how to access

composeResources

when composeApp.js is loaded on a non root path? I keep on getting

MissingResourceException: Missing resource with path: ./composeResources/my.package.name/drawable/compose-multiplatform.xml

Albert

07/25/2025, 7:56 AM

Hi all, is it possible that with Kotlin JVM (setup with maven) to include wasm libraries from other projects, using it for back-end project? Can't find resources about it, only find things about compose

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mbonnin

07/28/2025, 5:47 PM

How do you test

browser

node

given that https://youtrack.jetbrains.com/issue/KT-60802 is still an issue? Do you test only a single environment? Do a separate project specifically for testing the other environment? Something else?

Alexey Zolotarev

07/30/2025, 12:42 PM

Hi, is it possible to get exceptions stacktrace when an error happens inside Kotlin 2.2.0-compiled Wasm (executed in NodeJS, old version of Exception Handling proposal)? The stacktrace seems be absent and debugging exceptions without a message like NPEs that happen somewhere is inconvenient to say the least. Not clear from the EH proposal if this is supported by the proposal itself but please advise if there are any debugging means that make it easier to localize the place where an exception is thrown other than using a bunch of `println`'s

Michael Paus

07/31/2025, 10:03 AM

I am just trying to understand how to use the APIs provided by the kotlin-wrappers project. As an example I have picked the kotlin-jszip module. I tried to convert the initial example given in https://stuk.github.io/jszip/ to Kotlin but somehow I got stuck. It took me already quite some time to find out about this “unsafeJso” function. I finally failed to convert the async stuff. Can anybody help me with that. Code so far inside the thread.

eygraber

07/31/2025, 8:16 PM

Why are pre-release versions of Kotlin being used in released libraries (kotlinx-browser in this case):

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w: The version of the Kotlin/Wasm standard library (2.2.20-Beta2-release-177) differs from the version of the compiler (2.2.0). Please, note that while Kotlin/Wasm is in active development phase only matching versions are supported.
Please, make sure that the standard library has the same version as the compiler. Adjust your project's settings if necessary.
e: warnings found and -Werror specified

chrisjenx

08/02/2025, 2:09 AM

Is it expected that if a composeResource file fails to load on wasmJs/js, it will completely stop composition and kill the ui? Dunno if there is a safer way to handle resource loading? Minus pre caching everything which seems a little heavy handed?

Piotr Krzemiński

08/02/2025, 9:44 PM

Hi! I'm trying to read a ZIP from within Wasm/JS. I thought about using https://github.com/nodeca/pako through JS interop, however I'm getting the following problem when calling the library, the full stack trace is in the thread. The code is here. It's almost identical to what's done in Ashampoo's kim (code). @Stefan Oltmann maybe you have an idea what's wrong?

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