Can I get exception stacktrace in kotlin-js?

Question

I've been writing simple web-frontend for application with kotlin-js and faced with a problem of exception handling. As I see, there is no API to get exception stacktrace: https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-throwable/index.html Is it so? If it is, may be anyone know some library or snippets to get stacktrace out of Throwable object?

Currently, I've got some workaround for this:

import kotlin.browser.window

fun main() {
    window.onload = {
        try {
            throw RuntimeException()
        } catch (e: Throwable) {
            console.log(e)
            throw e
        }
    }
}

Console output is:

Object { 
"message_8yp7un$_0": null, 
"cause_th0jdv$_0": null, 
"stack": "captureStack@http://localhost:9080/js/kotlin.js:1767:27\nException@http://localhost:9080/js/kotlin.js:3244:14\nRuntimeException@http://localhost:9080/js/kotlin.js:3255:17\nRuntimeException_init@http://localhost:9080/js/kotlin.js:3261:24\nmain$lambda@http://localhost:9080/js/web-client.js:34:13\n",
"name": "RuntimeException"
}

Here, console.log(Throwable) exposes underlying JavaScript object properties, and there is stack one, but it points to JavaScript code, that is hard to use without source mapping back to kotlin.

UPD: it seems like stack is not standard exception property, but common one for modern browsers.

r33tnup · Accepted Answer · 2020-11-11 11:54:51Z

4

Since Kotlin 1.4 the stdlib contains two extensions for this exact purpose fun Throwable.stackTraceToString()
fun Throwable.printStackTrace()

Using these we can write

    window.onload = {
        try {
            throw RuntimeException()
        } catch (e: Throwable) {
            e.printStackTrace()
        }
    }

answered Nov 11, 2020 at 11:54

r33tnup

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Comments

groenhen · Accepted Answer · 2020-06-16 05:26:45Z

1

Not perfect, not standard, but it works.
It also handles the source map in Firefox, so I get proper file names and line numbers:

try {
    throw IllegalStateException("ops...")
} 
catch (ex : Throwable) {
    val stack = ex.asDynamic().stack
    if (stack is String) {
        val error = js("Error()")
        error.name = ex.toString().substringBefore(':')
        error.message = ex.message?.substringAfter(':')
        error.stack = stack
        console.error(error)
    } else {
        console.log(ex)
    }
}

edited Jun 16, 2020 at 5:26

groenhen

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answered Jun 16, 2020 at 4:57

tiz

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Comments

andylamax · Accepted Answer · 2019-07-11 09:09:00Z

0

Just change your console.log to console.error

import kotlin.browser.window

fun main() {
    window.onload = {
        try {
            throw RuntimeException()
        } catch (e: Throwable) {
            console.error(e) // change here
            throw e
        }
    }
}

answered Jul 11, 2019 at 9:09

andylamax

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