Hi, I try to use a npm package in a mpp project. ...

# javascript

[Patrick Doering]

Hi,
I try to use a npm package in a mpp project.

Like from the example:
dependencies {
    // ...
    implementation(npm("is-sorted", "1.0.5"))
}

@JsModule("is-sorted")
@JsNonModule
external fun <T> sorted(a: Array<T>): Boolean

console.log("Hello, Kotlin/JS!")
console.log(sorted(arrayOf(1,2,3)))
console.log(sorted(arrayOf(3,1,2)))

Now I wanna use another npm library with the name kafkjs in that way:

dependencies {
    // ...
   implementation (npm( "kafkajs", "^1.12.0"))
}

fun createConsumer(): dynamic {
return js(
“kafka.consumer({groupID: ‘test-group’ })”
)
}

but I alwas get the error:

ReferenceError: kafka is not defined

Any ideas what I am doing wrong?

[turansky]

Main problem - no kafka declarations

// declarations
@JsModule("kafka")
external object kafka {
    fun consumer(options: ConsumerOptions): dynamic
}

external interface ConsumerOptions {
    var groupID: String
}

// code
fun createConsumer(): dynamic {
val options: ConsumerOptions = js("({})")
options.groupID = "test-group"
return kafka.consumer(options)
}

[turansky]

Declarations required for “autoimport”

[Patrick Doering]

Thank you for the help.
Now I get another error:
Cannot find module 'kafka'
When I am right, it comes that the module should be kafkajs.
In JS I use this with: const { Kafka } = require('kafkajs')

When I change that it comes to a TypeError: $module$kafkajs.consumer is not a function

But I don`t understand why, at the moment.

[Ilya Goncharov [JB]]

In fact you require not consumer but Kafka
So in fact in external declaration you have

@file:JsModule(“kafkajs”) // file means that all further external declarations will be found as a subobject on “kafkajs”

external object Kafka {
   fun consumer(...)
}

[Patrick Doering]

That means this should run:

@JsModule("kafkajs")
@JsNonModule
external object Kafka {
    fun consumer(options: ConsumerOptions): dynamic
}

external interface ConsumerOptions {
    var groupID: String
}

fun createConsumer(): dynamic {
    val options: ConsumerOptions = js("({})")
    options.groupID = "test-group"

    return Kafka.consumer(options)
}

But with this I get the TypeError.
TypeError: $module$kafkajs.consumer is not a function

[Ilya Goncharov [JB]]

In your decision, you mark external object with @JsModule . It means that all your external object looked as a JsModule. It is similar with JS code

const { consumer } = require("kafkajs")

But you need if I understand correctly

const { Kafka } = require("kafkajs")
const consumer = Kafka.consumer

For this you can mark all file with @JsModule telling that all external declarations are part of JsModule

@file:JsModule("kafkajs") // file: is important!

external object Kafka {
    fun consumer(options: ConsumerOptions): dynamic
}
external interface ConsumerOptions {
    var groupID: String
}

[Patrick Doering]

Ok now im lost. When I mark the file with @JsModule how can I pass the configuration options to the consumer? I mean the original function is not usable any more.

fun createConsumer(): dynamic {
    val options: ConsumerOptions = js("({})")
    options.groupID = "test-group"

    return Kafka.consumer(options)
}

And how should my call from NodeJS look like?
Please excuse the many questions I am completely new in Kotlin / JS and I want to learn and understand it.

[Ilya Goncharov [JB]]

Yes, for now if you mark file with @JsModule it means that you can add only external declarations to this file, you can move non-external fun to another file.
In all other questions it should be completely the same

[turansky]

@Patrick Doering Also you can vote here - https://youtrack.jetbrains.com/issue/KT-37776 🙂

[Patrick Doering]

@Ilya Goncharov [JB] as I see it right in the documentation I need following:

const kafka = new Kafka({
  clientId: 'my-app',
  brokers: ['kafka1:9092', 'kafka2:9092']
})
 
const producer = kafka.producer()
const consumer = kafka.consumer({ groupId: 'test-group' })

If I understand you right I have to implement it in that way:

File: KafkaImpl.kt

@file:JsModule("kafkajs") // file: is important!

package <myCoolPackage>

external object Kafka {
    fun producer(): dynamic
    fun consumer(options: ConsumerOptions): dynamic
}
external interface ConsumerOptions {
    var groupID: String
}

and another File: KafkaInitialisation.kt

fun createConsumer(): dynamic {
    val options: ConsumerOptions = js("({})")
    options.groupID = "test-group"
    return Kafka.consumer(options)
}

fun createProducer(): dynamic {
    return Kafka.producer()
}

And call them from node with:

const myKafka = require('../build/js/packages/kafkaDemo').de.kafkaDemo.kafka;
async function testCall() {
  const producer = myKafka.createProducer();
  const consumer = myKafka.createConsumer();
}

testCall();

Is that right?

[Ilya Goncharov [JB]]

Yes, it is right
If you are interesting in integration with external JS project, you can check it, maybe it will be useful
https://github.com/ilgonmic/kotlin-ts

[Patrick Doering]

Thank you. So I implemented in that way and it is actual not running. I always get the error.
UnhandledPromiseRejectionWarning: TypeError: Kafka.producer is not a function

I will check your repo. And hopefully find a solution.

[Patrick Doering]

I don`t see my error.
Everytime when I try it is not working.
https://github.com/munichbughunter/callJSLib

[Ilya Goncharov [JB]]

As I can see, kafkajs initially requires to create Kafka instance, and only after that to call producer and consumer on instance.
So it means that in your external declarations Kafka should be class
But I can recommend to use dukat , you can send third parameter into npm dependency

implementation(npm("kafkajs", "...", true))

and it include generated external declarations into your build.

There is small trick, because kafkajs uses @types/nodejs , dukat can’t generate it, but we have nodejs declarations here (https://github.com/Kotlin/kotlinx-nodejs), you can have dependency on it

[Ilya Goncharov [JB]]

And it requires to make changes in your KafkaInitialisation something like this

fun createConsumer(): dynamic {
    val options: KafkaConfig = js("({})")
    val consumerOptions: ConsumerConfig = js("({})")
    consumerOptions.groupId = "test-group"
    return Kafka(options).consumer(consumerOptions)
}

fun createProducer(): dynamic {
    val options: KafkaConfig = js("({})")
    return Kafka(options).producer()
}

[Ilya Goncharov [JB]]

But honestly, now I see that dukat generates a bit errors (it does not provide @JsModule annotation in this case cc @[JB] Shagen)
So you can use manual task *generateExternals and find declarations in folder externals and copy it inside your sources, and make all necessary changes

[Patrick Doering]

I will evaluate or later. I have kiddies Time. 😅

[Ilya Goncharov [JB]]

Seems that something work here (https://github.com/ilgonmic/callJSLib) - Kafka error, but it seems that it is kafka related specific

I can reach it with next steps
1. Add kotlinx-nodejs dependency
2. Run task nodeJsGenerateExternals
3. Copy from externals to sources
4. Add to index.module_kafkajs.kt on top @file:JsModule("kafkajs")
5. Move all typealiases (non external) to other file (in my case index.module_kafkajs2.kt

[Patrick Doering]

Wohoo @Ilya Goncharov [JB] it works now. Really really great.
Thanks for all the help in my journey of learning Kotlin/JS (and particularly using it in nodeJS). Great learning experience for me.