Question: How do I access FileSystem in wasmJs?

[stepango]

I'm using following multiplatform configuration for wasm target

wasmJs {
    binaries.executable()
    nodejs()
}

trying to add nodefilesystem dep

sourceSets {
    val wasmJsMain by getting {
        dependencies {
            implementation("com.squareup.okio:okio-nodefilesystem:3.9.0")
        }
    }
 }

But getting following error

Could not determine the dependencies of task ':kotlinNpmInstall'.
> Could not resolve all dependencies for configuration ':llama2:wasmJsNpmAggregated'.
  > Could not resolve com.squareup.okio:okio-nodefilesystem:3.9.0.
    Required by:
        project :llama2
     > No matching variant of com.squareup.okio:okio-nodefilesystem:3.9.0 was found. The consumer was configured to find a library for use during 'kotlin-runtime', preferably optimized for non-jvm, as well as attribute 'org.jetbrains.kotlin.platform.type' with value 'wasm', attribute 'org.jetbrains.kotlin.js.public.package.json' with value 'public-package-json', attribute 'org.jetbrains.kotlin.wasm.target' with value 'js' but:
         - Variant 'commonFakeApiElements-published' capability com.squareup.okio:okio-nodefilesystem:3.9.0:
             - Incompatible because this component declares a component for use during 'kotlin-api', as well as attribute 'org.jetbrains.kotlin.platform.type' with value 'common' and the consumer needed a component for use during 'kotlin-runtime', as well as attribute 'org.jetbrains.kotlin.platform.type' with value 'wasm'
             - Other compatible attributes:
                 - Doesn't say anything about its component category (required a library)
                 - Doesn't say anything about its target Java environment (preferred optimized for non-jvm)
                 - Doesn't say anything about org.jetbrains.kotlin.js.public.package.json (required 'public-package-json')
                 - Doesn't say anything about org.jetbrains.kotlin.wasm.target (required 'js')
         - Variant 'jsApiElements-published' capability com.squareup.okio:okio-nodefilesystem:3.9.0 declares a library:
             - Incompatible because this component declares a component for use during 'kotlin-api', as well as attribute 'org.jetbrains.kotlin.platform.type' with value 'js' and the consumer needed a component for use during 'kotlin-runtime', as well as attribute 'org.jetbrains.kotlin.platform.type' with value 'wasm'
             - Other compatible attributes:
                 - Doesn't say anything about its target Java environment (preferred optimized for non-jvm)
                 - Doesn't say anything about org.jetbrains.kotlin.js.public.package.json (required 'public-package-json')
                 - Doesn't say anything about org.jetbrains.kotlin.wasm.target (required 'js')
         - Variant 'jsRuntimeElements-published' capability com.squareup.okio:okio-nodefilesystem:3.9.0 declares a library for use during 'kotlin-runtime':
             - Incompatible because this component declares a component, as well as attribute 'org.jetbrains.kotlin.platform.type' with value 'js' and the consumer needed a component, as well as attribute 'org.jetbrains.kotlin.platform.type' with value 'wasm'
             - Other compatible attributes:
                 - Doesn't say anything about its target Java environment (preferred optimized for non-jvm)
                 - Doesn't say anything about org.jetbrains.kotlin.js.public.package.json (required 'public-package-json')
                 - Doesn't say anything about org.jetbrains.kotlin.wasm.target (required 'js')
         - Variant 'jsSourcesElements-published' capability com.squareup.okio:okio-nodefilesystem:3.9.0 declares a component for use during 'kotlin-runtime':
             - Incompatible because this component declares documentation, as well as attribute 'org.jetbrains.kotlin.platform.type' with value 'js' and the consumer needed a library, as well as attribute 'org.jetbrains.kotlin.platform.type' with value 'wasm'
             - Other compatible attributes:
                 - Doesn't say anything about its target Java environment (preferred optimized for non-jvm)
                 - Doesn't say anything about org.jetbrains.kotlin.js.public.package.json (required 'public-package-json')
                 - Doesn't say anything about org.jetbrains.kotlin.wasm.target (required 'js')

Which kind of makes sense.

Is there any option for wasmJs to read from real fs the same way it works for js targets?

[swankjesse]

Try wasmWasi ?

[swankjesse]

We expose the Node FileSystem in Kotlin/JS only. For WASM we have the WASI FileSystem, which is needs its directories to be specified.

[JakeWharton]

Or if you're in a browser you have to use the JS file system API directly and can't use Okio: https://developer.mozilla.org/en-US/docs/Web/API/File_System_API. In that case you can wrap your file system interactions in a higher-level suspending interface and switch between Okio and native JS implementations.

[ApoloApps]

@JakeWharton will there be in the future a okio-fs wrapper around browser's filesystem apis (without node)?

[JakeWharton]

No. Okio's file system API only supports contexts where it can be used in a synchronous, blocking manner.