nest-kotlin

A proof-of-concept project exploring interop between NestJS, TypeScript and KotlinJS.

Overview

What It Does

Demonstrates a Kotlin-first code sharing mechanism, where data models and business logic can be defined in Kotlin and utilized in Nest.

What it Doesn't Do

Interaction with TypeScript files from Kotlin is not currently supported and as a result, neither is definition of Nest modules & controllers in Kotlin.

Example

foo.kt

package foo

fun getFoo():String {
    return "Foo!"
}

foo.controller.ts

import * as interop from "interop"

@Controller()
export class FooController {
    constructor() {}

    @Get('foo')
    async get(@Request() req, @Response() res, next) {
        res.status(HttpStatus.OK).send(interop.foo.getFoo());
    }
}

How It Works

• Interoperation is achieved by targeting JS when compiling Kotlin, and then generating TypeScript definitions for the JS output.
• The project can be built and run with npm start and npm run start:prod similar to the other starter repos.
• Kotlin is compiled to JS via Gradle and the included Gradle wrapper. KotlinJS configuration can be seen in build.gradle.
• The NPM scripts which define the build process can be viewed in package.json.

Build Process

1. Compiles Kotlin to JS by calling ./gradlew assemble, outputting a CommonJS module that's ready to use with Node
2. Calls dtsmake to generate typings from the JS output, complete with realistic types thanks to type inference
3. Uses shx to copy the JS output to npm_modules so it can be imported by Node - this could use a second look.
4. Calls tsc
5. Runs with node index.js or node dist/server.js

Dependencies

In addition to NPM, the JRE/JDK will also be required to run the gradle build and compile the Kotlin code. Use of IntelliJ IDEA is highly recommended for working with Kotlin.

Should I Use This?

Probably not.