Angular 6 typescript integration with KotlinJs

Question

I have just managed to import Kotlin compiled javascript module in an angular 6 typescript file. It was not easy and the result confuses me. I wanna know if more elegant way exists.

Originally I take a Kotlin file:

package com.example.test

data class SomeInterface(
    var id: String? = null,
    var value: String? = null
) {
}

It well compiles to the following JavaScript

(function (root, factory) {
  if (typeof define === 'function' && define.amd)
    define(['exports', 'kotlin'], factory);
  else if (typeof exports === 'object')
    factory(module.exports, require('kotlin'));
  else {
    if (typeof kotlin === 'undefined') {
      throw new Error("Error loading module 'TestKotlinCompiled'. Its dependency 'kotlin' was not found. Please, check whether 'kotlin' is loaded prior to 'TestKotlinCompiled'.");
    }
    root.TestKotlinCompiled = factory(typeof TestKotlinCompiled === 'undefined' ? {} : TestKotlinCompiled, kotlin);
  }
}(this, function (_, Kotlin) {
  'use strict';
  var Kind_CLASS = Kotlin.Kind.CLASS;
  function SomeInterface(id, value) {
    if (id === void 0)
      id = null;
    if (value === void 0)
      value = null;
    this.id = id;
    this.value = value;
  }
  SomeInterface.$metadata$ = {
    kind: Kind_CLASS,
    simpleName: 'SomeInterface',
    interfaces: []
  };
  SomeInterface.prototype.component1 = function () {
    return this.id;
  };
  SomeInterface.prototype.component2 = function () {
    return this.value;
  };
  SomeInterface.prototype.copy_rkkr90$ = function (id, value) {
    return new SomeInterface(id === void 0 ? this.id : id, value === void 0 ? this.value : value);
  };
  SomeInterface.prototype.toString = function () {
    return 'SomeInterface(id=' + Kotlin.toString(this.id) + (', value=' + Kotlin.toString(this.value)) + ')';
  };
  SomeInterface.prototype.hashCode = function () {
    var result = 0;
    result = result * 31 + Kotlin.hashCode(this.id) | 0;
    result = result * 31 + Kotlin.hashCode(this.value) | 0;
    return result;
  };
  SomeInterface.prototype.equals = function (other) {
    return this === other || (other !== null && (typeof other === 'object' && (Object.getPrototypeOf(this) === Object.getPrototypeOf(other) && (Kotlin.equals(this.id, other.id) && Kotlin.equals(this.value, other.value)))));
  };
  var package$com = _.com || (_.com = {});
  var package$example = package$com.example || (package$com.example =     {});
  var package$test = package$example.test || (package$example.test = {});
  package$test.SomeInterface = SomeInterface;
  Kotlin.defineModule('TestKotlinCompiled', _);
  return _;
}));

In package.json I add "kotlin": "^1.2.70", to the dependencies section. In angular component I have to use such a code for import.

import * as TestKotlinCompiled from "../../generated/TestKotlinCompiled";

// @ts-ignore
const SomeInterface = TestKotlinCompiled.com.example.test.SomeInterface;
// @ts-ignore
type SomeInterface = TestKotlinCompiled.com.example.test.SomeInterface;

This is minimal mandatory code to use class SomeInterfac in the package com.example.test generated to the module TestKotlinCompiled.

The problems here are following.

// @ts-ignore is required because at the compile time the ts-comiler does not see the content of the module being imported.

const is required for new SomeInterface()

type is required for let x: SomeInterface;

All these look terribly hacky. I wold like something easier like import {SomeInterface} from '../../generated/TestKotlinCompiled' using namespace com.example.test without const and type. So, is there a way to simplify my above code?

Answer 1

I too had a go and solving this integration, There are a number of issues to overcome, i.e.

• generating typescript declaration files
• unpacking kotlin JS modules into node_modules
• third-party libraries

Blog post describing the issues is here https://medium.com/@dr.david.h.akehurst/building-applications-with-kotlin-and-typescript-8a165e76252c

I also created a gradle plugin that make it all alot easier, https://github.com/dhakehurst/net.akehurst.kotlin.kt2ts

Answer 2

I succeeded to improve little bit usability of KotlinJs in Angular. I dispose my experiments in https://github.com/svok/kotlin-multiplatform-sample

First, we must create a multiplatform submodule in Gradle. In that we generate js files (among other possible platforms).

Then we add to package.json...

{
  "dependencies": {
    "kotlin": "^1.3.21",
    "proj-common": "file:../build/javascript-compiled"
  }
}

proj-common is our compiled Kotlin module. The path there is where kotlin-js files are built to.

Thus, in typescript we just use one more npm module

import {sample} from 'proj-common/proj-common';

// For class Sample
sample = new sample.Sample();

// For object Platform
platform = sample.Platform;

Compilation goes well with no neсessity to use // @ts-ignore

Update

In the above explanation there was a problem with subdependencies. They were not exported, but not all subdependencies have their equivalents in npm repository. The below code solves this problem.

tasks {
    task<Sync>("assembleWeb") {
        val dependencies = configurations.get("jsMainImplementation").map {
            val file = it
            val (tDir, tVer) = "^(.*)-([\\d.]+-\\w+|[\\d.]+)\\.jar$"
                .toRegex()
                .find(file.name)
                ?.groupValues
                ?.drop(1)
                ?: listOf("", "")
            var jsFile: File? = null
            copy {
                from(zipTree(file.absolutePath), {
                    includeEmptyDirs = false
                    include { fileTreeElement ->
                        val path = fileTreeElement.path
                        val res = (path.endsWith(".js") || path.endsWith(".map"))
                                && (path.startsWith("META-INF/resources/") || !path.startsWith("META-INF/"))
                        if (res && path.endsWith(".js") && ! path.endsWith(".meta.js")) jsFile = fileTreeElement.file
                        res
                    }
                })
                into("$npmTarget/$tDir")
            }
            jsFile?.also { packageJson(tDir, it, tVer) }
            tDir to jsFile
        }
            .filter { it.second != null }
            .map { it.first to it.second!! }
            .toMap()

        packageJson(npmDir, File(jsOutputFile), project.version.toString(), dependencies)
        dependsOn("jsMainClasses")
    }

    assemble.get().dependsOn("assembleWeb")
}

fun packageJson(dir: String, jsFile: File, version: String, dependencies: Map<String, File> = emptyMap()) {
    val deps = dependencies.map {
        """"${js2Name(it.value)}": "file:../${it.key}""""
    }.joinToString(",\n            ")
    val text = """
        {
          "name": "${js2Name(jsFile)}",
          "version": "${version}",
          "main": "./${jsFile.name}",
          "dependencies": {
            ${deps}
          }
        }
    """.trimIndent()
    File("$npmTarget/$dir/package.json").apply {
        if (parentFile.exists()) {
            parentFile.delete()
        }
        parentFile.mkdirs()
        writeText(text)
    }
}

fun js2Name(jsFile: File) = jsFile.name.replace("""\.js$""".toRegex(), "")

Then, import from the front submodule:

{
  "dependencies": {
    "proj-common": "file:../build/npm"
  }
}

And in the typescript file:

import {sample} from 'proj-common';

// For class Sample
sample = new sample.Sample();

// For object Platform
platform = sample.Platform;

The sample project see at https://github.com/svok/kotlin-multiplatform-sample

Update 2

Now you can create full stack projects with kotlin common subproject as easy as just attaching a plugin in gradle

plugins {
    id("com.crowdproj.plugins.jar2npm")
}

This plugin will automatically inject all your kotlin-js jar packages into your node_modules during compilation.

The https://github.com/svok/kotlin-multiplatform-sample project is now rewritten with this plugin. See proj-angularfront submodule.