如何修复“未找到它的依赖项 'kotlinx-coroutines-core'。”

Question

I followed this tutorial to create a kotlin->js project: https://kotlinlang.org/docs/tutorials/javascript/getting-started-gradle/getting-started-with-gradle.html

Next, I followed these instructions to use coroutines in my code: https://github.com/kotlin/kotlinx.coroutines/blob/master/README.md#using-in-your-projects

Everything was fine to far, no errors marked in the code and I could build my js application without any error messages. However, my js scripts are not running in the browser and I get the above mentioned error message in the browser console. Does any of you here know what I missed or might have configured wrong?

Here's my build.gradle

group 'de.berlin'
version '1.0-SNAPSHOT'

buildscript {
    ext.kotlin_version = '1.3.31'
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
    }
}

apply plugin: 'kotlin2js'

repositories {
    mavenCentral()
}

dependencies {
    compile "org.jetbrains.kotlin:kotlin-stdlib-js:$kotlin_version"
    testCompile "org.jetbrains.kotlin:kotlin-test-js:$kotlin_version"
    compile "org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.0-M1"
    compile("org.jetbrains.kotlinx:kotlinx-coroutines-core-common:1.3.0-M1")
    compile "org.jetbrains.kotlinx:kotlinx-coroutines-core-js:1.3.0-M1"
}

compileKotlin2Js.kotlinOptions.sourceMap = true
compileKotlin2Js.kotlinOptions.outputFile = "${projectDir}/web/js/myApp.js"
compileKotlin2Js.kotlinOptions.suppressWarnings = false
compileKotlin2Js.kotlinOptions.verbose = true

build.doLast {
    configurations.compile.each { File file ->
        copy {
            includeEmptyDirs = false

            from zipTree(file.absolutePath)
            into "${projectDir}/web/js/lib"
            include { fileTreeElement ->
                def path = fileTreeElement.path
                path.endsWith(".js") && (path.startsWith("META-INF/resources/") || !path.startsWith("META-INF/"))
            }
        }
    }

    copy {
        includeEmptyDirs = false
        from "${buildDir}/resources/main"
        into "${projectDir}/web"
    }
}

clean.doFirst {
    delete "${projectDir}/web"

}

Everything compiles without any error message but I get the following error message in the browser console: ""Its dependency 'kotlinx-coroutines-core' was not found. Please, check whether 'kotlinx-coroutines-core' is loaded prior to '(projectname)'."

A more detailled inspection shows that /web/js/lib only contains kotlin.js, shouldn't kotlinx-coroutines-core be also there because it's part of the depencency block and schould be copied in the build.doLast-step? I also noticed that the comiled js file contains the following:

if (typeof kotlin === 'undefined') {
  throw new Error("Error loading module 'myApp'. Its dependency 'kotlin' was not found. Please, check whether 'kotlin' is loaded prior to 'myApp'.");
}
if (typeof this['kotlinx-coroutines-core'] === 'undefined') {
  throw new Error("Error loading module 'myApp'. Its dependency 'kotlinx-coroutines-core' was not found. Please, check whether 'kotlinx-coroutines-core' is loaded prior to 'myApp'.");
}

Why is it this['kotlinx-coroutines-core'] and not kotlinx-coroutines-core (like in the line above)?

Answer 1

Why is it this['kotlinx-coroutines-core'] and not kotlinx-coroutines-core (like in the line above)?

Because "kotlinx-coroutines-core" is not a valid JS identifier.

"this['kotlinx-coroutines-core']" is testing whether the module "kotlinx-coroutines-core" has been loaded or not.

if it is undefined, then it means you have not 'loaded' the module prior to the code being executed.

depending how you load JS modules, you will need to "require(....)" or have an html script reference to the "kotlinx-coroutines-core" module

Answer 2

It has been more than a year and a half since the thread was opened but I answer in case someone has the same problem in the future.

You have to download "kotlinx-coroutines-core" from npm. Coroutines JS - install