Gradle configuration error: Cannot add extension with name 'kotlinNodeJs'

[alshan]

In multiplatform project which is also muiltiproject: as soon as I add id 'kotlinx-serialization' version '1.3.40' to plugins of one of subprojects, gradle can no longer configure other subprojects and fails with the following error:

Cannot add extension with name 'kotlinNodeJs', as there is an extension already registered with that name.

Environment

• Kotlin version: 1.3.40
• Kotlin platforms: Multiplatform
• Gradle version: 4.10.3

[sandwwraith]

Can you post whole contents of your build.gradle, please? Or just give a link to github/gist with your project

[alshan]

This is the entire project: datalore-plot
See: base/build.gradle

[sandwwraith]

I'm still investigating the issue (this is more about Gradle infrastructure and new JS multiplatform plugin rather than serialization), but as a workaround, you can try to include both kotlin and serialization plugins to the root project (use apply false if necessary) and let me know if that works for you

[alshan]

When both plugins are in root project (with apply false) all subprojects are configured with no errors, thank you!

Unfortunately, I wasn't able to deserialize JSON to Map<String, Any>.

I've tried to use Json.parseMap<String, Any>(s) but got

SerializationException:

Can't locate argument-less serializer for class null. For generic classes, such as lists, please provide serializer explicitly.

JSON I needed to parse:

{   "data":    {      "time": ["Lunch","Lunch", "Dinner", "Dinner", "Dinner"]   }           ,   "mapping": {             "x": "time"           },   "layers": [               {                  "geom": "bar"               }           ]}

Aren't you supporting lists in values?

It was JS target. BWT, name kotlinx-serialization-kotlinx-serialization-runtime.js looks a bit weird)

[sandwwraith]

Yes, but for security reasons, we don't support deserializing to arbitrary Any. You can use Map<String, JsonElement> (i.e. JsonObject) to deserialize to Json AST or take a look at polymorphic deserialization which requires to list all possible classes in advance: https://github.com/Kotlin/kotlinx.serialization/blob/master/runtime/commonMain/src/kotlinx/serialization/Polymorphic.kt#L30

[alshan]

But this is just recursive map with strings, numbers and lists of the same types, which is very typical case I think.
Isn't this supposed to work out of the box?

[sandwwraith]

Well, when you read Any in the code, you usually think 'there could be any type', not 'there could be only strings, numbers, and maps'. That was the motivation behind design decision on supporting separate JsonObject instead of Map<String, Any>.

[alshan]

Up to you of course but string, number, boolean, null, object and array is pretty much all what JSON has. The default mapping would be: String, Double, Boolean, null, Map<String,*>, List<*>, and function Json.parseMap just looks like a perfect helper function with these defaults inside.

[eugenio1590]

I get this issue when I try to apply the plugin into a Kotlin JS project for browsers. This is the complete error:

Could not create an instance of type org.jetbrains.kotlin.gradle.targets.js.subtargets.KotlinBrowserJs.
> Failed to apply plugin [class 'org.jetbrains.kotlin.gradle.targets.js.nodejs.NodeJsRootPlugin']
   > Cannot add extension with name 'kotlinNodeJs', as there is an extension already registered with that name.

I am using these plugins:

plugins {
    id("org.jetbrains.kotlin.js") version "1.3.72"
    kotlin("plugin.serialization") version "1.3.72"
}

I tried to use (apply false) but this did not work.

[sandwwraith]

@eugenio1590 Try to use the plugin in the root module of your Gradle project. With apply: false if it is not really needed there

[eugenio1590]

I'll try it. I let you know If this issue persists. Thanks.

[eugenio1590]

I was able to replicate the problem. The issue occurs when I include a Kotlin multi-platform project with browser support in another that uses "kotlinx.serialization" library. I will create a project with that problem later.