How do sourcemaps work? If I create a simple proj...

# javascript

[CLOVIS]

How do sourcemaps work?

If I create a simple project and run jsBrowserDevelopmentRun , I get:
• build/js/packages/example-simple/kotlin/example-simple.js
• build/js/packages/example-simple/kotlin/example-simple.js.map
The second one contains:

{
	"version": 3,
	"sources": [
		"../../../../../src/jsMain/kotlin/Main.kt",
		"../../../../compileSync/js/main/developmentExecutable/kotlin/src/kotlin/util/Standard.kt"
	],
    // …

The Main.kt file refers to my own source code, fine.

However, I don't understand that Standard.kt file. The build/compileSync/js/main/developmentExecutable/kotlin folder does NOT contain a src/ folder, and there is no Standard.kt file anywhere in the build/ directory.

What's going on here?

[leonhardt]

In my experience, sourcemaps are broken when producing ECMAScript Modules. I filed this bug report a few months ago.
https://youtrack.jetbrains.com/issue/KT-76170/KJS-KMP-sourcemap-source-paths-are-broken-when-building-ECMAScript-modules
Does that issue match what you're seeing?

[CLOVIS]

I'm using the default configuration

[Edoardo Luppi]

It's "normal" as the compiler will process all files (be them sources or from klib metadata) under the compilation and will attempt to include them into the source map file. Obviously it can't link to a real source file.

[Edoardo Luppi]

Standard.kt refers to https://github.com/JetBrains/kotlin/blob/master/libraries/stdlib/src/kotlin/util/Standard.kt

[leonhardt]

@Edoardo Luppi actually, it seems that the JS build output for each module includes source files for the stdlib and other libraries, as needed (e.g. kotlin-kotlin-stdlib.mjs), so I think proper sourcemap linking should be possible. As far as we've been able to figure, there is just a bug that produces broken paths.

@Artem Kobzar did acknowledge the issue a couple months ago by marking it as planned so we've just patiently waiting (with broken source maps) in the meantime.