I have an Elixir module in which I am trying to call out to Pdfcpu to modify existing PDFs. Pdfcpu is written in Go and has a CLI and an API, and I am trying to use the API. I am using Wasmex to run the WASM code and interface with Elixir.

I have created a simple Go module:

package main

import (
    "log"

    "github.com/pdfcpu/pdfcpu/pkg/api"
)

func main() {
}

func RotateFile(inFile, outFile string, rotation int, selectedPages []string) {
    if err := api.RotateFile(inFile, outFile, rotation, []string{"1"}, nil); err != nil {
        log.Fatal(err)
    }
}

then ran

go mod init proj/pdfcpu
go get github.com/pdfcpu/pdfcpu@latest
go mod tidy
GOOS=wasip1 GOARCH=wasm go build -o main.go

To test, I ran a simple Elixir script

api_binary = File.read!("main.wasm")
{:ok, api_pid} = Wasmex.start_link(%{bytes: api_binary, wasi: true})

Wasmex.call_function(api_pid, "RotateFile", ["input.pdf", "output.pdf", 180, [], nil])

And I receive {:error, "exported function `RotateFile` not found"}

RotateFile is in the api package, so I tried calling “api.RotateFile” instead of “RotateFile”, but it made no difference.

What am I doing wrong?