[bug] Calling Rust from the frontend: invalid type

[thep0y]

Describe the bug

I have a function defined in main.ts that needs to be called in the frontend:

#[tauri::command]
fn close_conn() -> i8 {
    -1
}

fn main() {
    let context = tauri::generate_context!();
    tauri::Builder::default()
        .menu(if cfg!(target_os = "macos") {
            tauri::Menu::os_default(&context.package_info().name)
        } else {
            tauri::Menu::default()
        })
        .invoke_handler(tauri::generate_handler![close_conn])
        .run(context)
        .expect("error while running tauri application");
}

And call it in App.vue:

<script setup lang="ts">
import HelloWorld from './components/HelloWorld.vue'
import { invoke } from "@tauri-apps/api"

invoke('close_conn')
  .then((code) => alert(code))
  .catch((error) => console.error(error))

But, I got an error:

Reproduction

No response

Expected behavior

No response

Platform and versions

Environment
  › OS: Windows 10.0.22000 X64
  › Webview2: 103.0.1264.44
  › MSVC:
      - Visual Studio Community 2022
  › Node.js: 16.15.1
  › npm: 8.5.2
  › pnpm: Not installed!
  › yarn: 1.22.19
  › rustup: 1.24.3
  › rustc: 1.62.0
  › cargo: 1.62.0
  › Rust toolchain: stable-x86_64-pc-windows-msvc

Packages
  › @tauri-apps/cli [NPM]: 1.0.1
  › @tauri-apps/api [NPM]: 1.0.1
  › tauri [RUST]: 1.0.2,
  › tauri-build [RUST]: 1.0.2,
  › tao [RUST]: 0.12.1,
  › wry [RUST]: 0.19.0,

App
  › build-type: bundle
  › CSP: unset
  › distDir: ../dist
  › devPath: http://localhost:3000/
  › framework: Vue.js

App directory structure
  ├─ .vscode
  ├─ dist
  ├─ node_modules
  ├─ public
  ├─ src
  └─ src-tauri

Stack trace

No response

Additional context

No response

[FabianLars]

We have to manually overwrite the browser default alert function and our message dialog only supports strings.

Leaving this open for the team to decide if we want to add a toString() here