As long as I referred to the latest and old documents (listed below), they have never clarified the first value of the result array of wasi_ephemeral_args.get. Both wasmtime and wasmer actually put the wasm file's basename there, but that isn't documented yet. Due to the vagueness, Node.js's WASI implementation doesn't pass the basename unless the user explicitly pass as the args option.

For example:

Source file of the WASI executable (args.rs):

use std::env;

fn main() {
    println!("{:?}", env::args().collect::<Vec<String>>())
}

Node.js script to run the WASI file (run-wasi.mjs):

import fs from 'fs';
import { WASI } from 'wasi';

const [_node, _thisScript, wasmFile, ... args] = process.argv;

const wasi = new WASI({ args });
const importObject = { wasi_snapshot_preview1: wasi.wasiImport };

const wasm = await WebAssembly.compile(fs.readFileSync(wasmFile));
const instance = await WebAssembly.instantiate(wasm, importObject);

wasi.start(instance);

Example result by Node.js:

> node -v
v16.3.0
> node --experimental-wasi-unstable-preview1 run-wasi.mjs  path/to/args.wasm aaa bbb
(node:7950) ExperimentalWarning: WASI is an experimental feature. This feature could change at any time
(Use `node --trace-warnings ...` to show where the warning was created)
["aaa", "bbb"]

Example result by wasmtime:

> wasmtime --version
wasmtime 0.28.0
> wasmtime  path/to/args.wasm aaa bbb
["args.wasm", "aaa", "bbb"]

So I think we should specify the current behavior of wasmtime and wasmer in the document for consistency.

Ref.

• https://github.com/WebAssembly/wasi-classic-command/blob/5bacb3845eb16c37f036ce4a330201c8dc0defe9/phases/ephemeral/docs.md#-getargv-pointerpointeru8-argv_buf-pointeru8---result-errno
• https://github.com/WebAssembly/WASI/blob/main/phases/ephemeral/docs.md#-getargv-pointerpointeru8-argv_buf-pointeru8---result-errno
• https://github.com/WebAssembly/WASI/blob/main/phases/snapshot/docs.md#-args_getargv-pointerpointeru8-argv_buf-pointeru8---result-errno
• https://github.com/WebAssembly/WASI/blob/main/phases/old/snapshot_0/docs.md#-args_getargv-pointerpointeru8-argv_buf-pointeru8---result-errno