I have an external Wasm file named “rust_library.w...

# webassembly

[Michael Paus]

I have an external Wasm file named “rust_library.wasm” which exports a function “fibonacci”. Where do I have to place this file and what else has to be done to be able to directly import this function into Kotlin/wasmJs and thus avoid going through JS interop?

I have placed it into “.../src/wasmJsMain/resources” and imported the function like this:

@kotlin.wasm.WasmImport("rust_library", "fibonacci")
external fun calculateFibonacci(n: Int): Int

But at build time I only get

Module not found: Error: Can't resolve 'rust_library' in '/Users/mpaus/Projects/tmp/EmmentalerDemo/build/js/packages/composeApp/kotlin'

although this folder actually contains the Wasm file.

The Wasm file itself is correct because it works nicely in Chasm, Chickory and GraalVMWasm.

[Michael Paus]

I got it working myself. The correct way to import the module is:

@kotlin.wasm.WasmImport("./rust_library.wasm", "fibonacci")
external fun calculateFibonacci(n: Int): Int

So, the module here is actually a relative file path and not only the module name.

Calling this function like this

val fib = calculateFibonacci(10)
println("fib(10) = $fib (should be 55)")

actually produces

fib(10) = 55 (should be 55)

in the browser console 🎉.

Now let’s see whether I can also get less trivial code to work.