#[tauri::command] macro generates “defined multiple times” error when using lib.rs

I’m trying to create a Tauri app by moving some commands into lib.rs.

lib.rs

#[tauri::command]
pub async fn get_file_path_in_rust(file_path: String) {
    println!("The Path Received: {}", file_path);
}

main.rs

#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]

use tauri_plugin_opener::OpenerExt;
use whoami;
use crate::get_file_path_in_rust;

#[tauri::command]
fn get_user() -> String {
    whoami::username()
}

fn main() {
    tauri::Builder::default()
        .plugin(tauri_plugin_dialog::init())
        .plugin(tauri_plugin_opener::init())
        .invoke_handler(tauri::generate_handler![
            get_user,
            get_file_path_in_rust
        ])
        .run(tauri::generate_context!())
        .expect("error while running tauri app");
}

But when I run it, I get this error:

the name `__cmd__get_file_path_in_rust` is defined multiple times
`__cmd__get_file_path_in_rust` must be defined only once in the macro namespace of this module

I only have the function once, so I don’t understand why the macro is being generated twice.

Question:

What’s the correct way to put #[tauri::command] functions in lib.rs and call them from main.rs?

How do I avoid this duplicate macro error?