Browser Stdin auto pipes to Stdout.

[IbrahimTanyalcin]

Thank you for this nice package. I am currently trying to make it work with my wasm file in the browser. Here is some background:

I have a bash script that constantly listens to stdin and accumulates user input until a sequence of chars are encountered (____END____ in my case), the tty behavior is like below:

stdin  ===> {"a" 
stdout ===>{"a"
stdin  ===>  ____END____ 
stdout ===>{"a"____END____
stdout ===>{"type":"Error", "message": "Invalid JSON"}
stdin  ===> {"a":1,"b":2}____END____

stdout ===>success!!
stdout ===>{"type":"Error", "message": "Missing fields"}

Until I send SIGINT or similar. Now I converted this to a docker container (with openssl and all other deps with Alpine base image) and run:

docker run -it --rm --name app-test my-repo:my-tag

which replicates the behavior of the bash script 1 to 1. Next I converted the container to a wasm using container2wasm package using c2w binary. And run the resulting wasm using wasmtime:

wasmtime /home/user/path/to/out_alpine.wasm

and the above perfectly replicates the behavior of the bash script. So all 3 steps work. Next is using your package Wasmer to make it work in the browser. So on the main thread side I have this:

const worker = new Worker("static/js/worker.js", {type: "module"});

and on the worker side:

import { init, Wasmer } from "./wasmer-sdk.mjs"; //same as https://unpkg.com/@wasmer/[email protected]/dist/index.mjs, I also have wasmer_js_bg.wasm under the same path 'static/js/wasmer_js_bg.wasm'

let wasmInstance = null;
let wasmStdin = null;
let decoder = new TextDecoder();
let encoder = new TextEncoder();
let stdoutStream  = new WritableStream({
    write(chunk) {
        postMessage({ type: 'output', data: decoder.decode(chunk) + "--test" });
    }
});
let stderrStream   = new WritableStream({
    write(chunk) {
        postMessage({ type: 'error', data: decoder.decode(chunk) + "--err-test" });
    }
});

(async () => {
    await init({log: "trace"});
    try {
        // Fetch the WASM file as binary data
        const response = await fetch("/static/js/out_alpine.wasm");
        if (!response.ok) {
            throw new Error(`Failed to fetch WASM: ${response.statusText}`);
        }

        const binaryFile = new Uint8Array(await response.arrayBuffer());
        const wasmModule = await Wasmer.fromFile(binaryFile);
        const { entrypoint } = wasmModule;

        //wasmInstance = await entrypoint.run({args: ["/bin/bash", "./myscript.sh"], cwd:"/app"}); doesnt work
        //wasmInstance = await entrypoint.run({stdin: (new TextEncoder).encode('{"a":1,"b":2}____END____')}); doesnt work
        wasmInstance = await entrypoint.run();
        //await wasmInstance.wait(); throws null pointer passed to rust
        wasmStdin = wasmInstance.stdin?.getWriter();
        wasmInstance.stdout?.pipeTo(stdoutStream);
        wasmInstance.stderr?.pipeTo(stderrStream);
    } catch (err) {
        postMessage({ type: "error", data: err.message || "Unexpected Error!" });
    }
})().catch(err => postMessage({ type: "error", data: err.message || "Unexpected Error!" }));

onmessage = async (event) => {
    const { input } = event.data;
    try {
        if (wasmStdin) {
            await wasmStdin.write(encoder.encode(input));
            //await wasmStdin.close(); to force EOF and doing encoder.encode(input + "\n") does not work
        } else {
            throw new Error("WASM stdin is not initialized.");
        }
    } catch (err) {
        console.error("Error sending input:", err.message);
        postMessage({ type: 'error', data: err.message || "Unexpected Error!" });
    }
};

above does not throw an error, and in fact loads the wasm as I can see from the debug log, which I attached. My only problem is, when I postMessage to the worker, whatever I post is reflected back. I checked if wasmInstance.stdin or wasmInstance.stdout return the same pointer but no, they return different objects. So it all seems to be working accept the fact that when I postMessage
"abc____END_____", I get back "abc____END_____--test" into the DOM.

Why is stdin seems to be piped to stdout? What am I missing?
I attached the DEBUG log.
wasmer.log

Many thanks!

[gtg092x]

This is additionally happening to me. Stdio is broken if it's using the streaming APIs.