tauri-syntax-commands

Quick Reference

Command Definition (Rust)

Pattern	Syntax	Notes
Sync command	#[tauri::command] fn name() -> T	Runs on main thread
Async command	#[tauri::command] async fn name() -> T	Spawned on tokio runtime
Forced async	#[tauri::command(async)] fn name() -> T	Sync function on tokio runtime
Renamed args	#[tauri::command(rename_all = "snake_case")]	JS passes snake_case keys

Argument Types (Rust <- JS)

Rust Type	JS Type	Notes
i32, u64, f64	number	Direct mapping
bool	boolean	Direct mapping
String	string	Owned string
Vec<T>	T[]	Array to Vec
Option<T>	T | null | undefined	Nullable
PathBuf	string	Path string
Custom struct	object	Must #[derive(Deserialize)]

Return Types (Rust -> JS)

Rust Return	JS Result	Notes
()	void / null	No return value
T (Serialize)	T	Direct serialization
Result<T, E>	T or throw E	E must impl Serialize
Response	ArrayBuffer	Binary data bypass

Special Injected Parameters (NOT passed from JS)

Rust Parameter	Purpose	Example
app: AppHandle	Application handle	app.emit("event", data)
window: WebviewWindow	Calling window	window.label()
state: State<'_, T>	Managed state	state.inner()
request: tauri::ipc::Request	Raw IPC request	request.headers(), request.body()

Frontend invoke() API

Feature	Syntax
Import	import { invoke } from '@tauri-apps/api/core'
Basic call	await invoke('command_name')
With args	await invoke('cmd', { argName: value })
Typed return	await invoke<ReturnType>('cmd')
With headers	await invoke('cmd', args, { headers: {...} })
Binary data	await invoke('cmd', new Uint8Array([...]))

Critical Warnings

NEVER use snake_case keys in JS invoke() arguments -- Tauri auto-converts camelCase to snake_case. Passing { file_path: "x" } will NOT match Rust parameter file_path.

NEVER forget to implement Serialize on error types -- Result<T, E> requires E to implement Serialize to send errors to the frontend.

NEVER use &str parameters in async commands -- borrowed references cannot cross the async spawn boundary. Use String instead.

NEVER register commands with multiple invoke_handler() calls -- only the last one takes effect.

NEVER mark commands in lib.rs as pub -- glue code generation prevents it. Move to a separate module if pub is needed.

ALWAYS wrap invoke() calls in try/catch -- Rust Result::Err rejects the JS Promise.

ALWAYS use Channel<T> for streaming data instead of multiple events -- channels are tied to the command invocation and type-safe.

ALWAYS derive serde::Deserialize on custom argument types and serde::Serialize on custom return types.

---

Essential Patterns

Pattern 1: Basic Command (Rust + TypeScript)

// src-tauri/src/commands.rs
#[tauri::command]
pub fn greet(name: String) -> String {
    format!("Hello, {}!", name)
}

// src/main.ts
import { invoke } from '@tauri-apps/api/core';

const greeting = await invoke<string>('greet', { name: 'World' });
console.log(greeting); // "Hello, World!"

Pattern 2: Async Command with Error Handling

#[derive(Debug, thiserror::Error)]
enum Error {
    #[error(transparent)]
    Io(#[from] std::io::Error),
    #[error("not found: {0}")]
    NotFound(String),
}

// REQUIRED: Serialize impl for sending errors to frontend
impl serde::Serialize for Error {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where S: serde::ser::Serializer {
        serializer.serialize_str(self.to_string().as_ref())
    }
}

#[tauri::command]
async fn read_file(path: String) -> Result<String, Error> {
    let content = tokio::fs::read_to_string(&path).await?;
    Ok(content)
}

try {
    const content = await invoke<string>('read_file', { path: '/tmp/data.txt' });
    console.log(content);
} catch (error) {
    // error is the serialized string: "not found: ..." or "io error: ..."
    console.error('Failed:', error);
}

Pattern 3: Structured Error Types

For richer error handling on the frontend, use tagged enum serialization.

#[derive(serde::Serialize)]
#[serde(tag = "kind", content = "message")]
#[serde(rename_all = "camelCase")]
enum AppError {
    Io(String),
    NotFound(String),
    Unauthorized(String),
}

#[tauri::command]
async fn load_data(id: u32) -> Result<Data, AppError> {
    if id == 0 {
        return Err(AppError::NotFound("Item not found".into()));
    }
    Ok(Data { /* ... */ })
}

try {
    const data = await invoke<Data>('load_data', { id: 42 });
} catch (err: any) {
    // err = { kind: 'notFound', message: 'Item not found' }
    switch (err.kind) {
        case 'notFound':
            showNotFoundUI(err.message);
            break;
        case 'unauthorized':
            redirectToLogin();
            break;
        default:
            console.error('Unexpected error:', err);
    }
}

Pattern 4: Special Injected Parameters

These parameters are injected by Tauri -- the frontend does NOT pass them.

use tauri::{AppHandle, State, WebviewWindow};

#[tauri::command]
async fn complex_command(
    app: AppHandle,                       // injected: app handle
    window: WebviewWindow,                // injected: calling window
    state: State<'_, MyState>,            // injected: managed state
    // Regular parameters (passed from JS):
    query: String,
    limit: Option<u32>,
) -> Result<Vec<Item>, String> {
    println!("Called from window: {}", window.label());
    let config = state.inner();
    // ... use app, window, state as needed
    Ok(vec![])
}

// Frontend only passes the regular parameters -- injected params are omitted
const items = await invoke<Item[]>('complex_command', {
    query: 'search term',
    limit: 10,
});

Pattern 5: Channel Streaming (Rust -> JS)

use tauri::ipc::Channel;

#[derive(Clone, serde::Serialize)]
struct DownloadProgress {
    bytes_read: u64,
    total: u64,
    percent: f64,
}

#[tauri::command]
async fn download_file(
    url: String,
    on_progress: Channel<DownloadProgress>,
) -> Result<String, String> {
    let response = reqwest::get(&url).await.map_err(|e| e.to_string())?;
    let total = response.content_length().unwrap_or(0);
    let mut bytes_read = 0u64;

    // Stream progress updates
    on_progress.send(DownloadProgress {
        bytes_read,
        total,
        percent: 0.0,
    }).unwrap();

    // ... read chunks, updating progress ...

    Ok("download complete".into())
}

import { invoke, Channel } from '@tauri-apps/api/core';

interface DownloadProgress {
    bytesRead: number;
    total: number;
    percent: number;
}

const onProgress = new Channel<DownloadProgress>();
onProgress.onmessage = (progress) => {
    updateProgressBar(progress.percent);
    console.log(`${progress.bytesRead}/${progress.total}`);
};

const result = await invoke<string>('download_file', {
    url: 'https://example.com/file.zip',
    onProgress,  // Pass the channel as a regular argument
});

Pattern 6: Binary Data with Request/Response

Bypass JSON serialization for large binary payloads.

use tauri::ipc::{Request, Response};

// Receiving binary data from JS
#[tauri::command]
fn upload(request: Request) -> Result<String, String> {
    let tauri::ipc::InvokeBody::Raw(data) = request.body() else {
        return Err("Expected binary data".into());
    };
    let auth = request.headers().get("Authorization");
    println!("Received {} bytes", data.len());
    Ok(format!("Uploaded {} bytes", data.len()))
}

// Returning binary data to JS
#[tauri::command]
fn get_image(path: String) -> Response {
    let data = std::fs::read(path).unwrap();
    Response::new(data)
}

// Sending binary data
const data = new Uint8Array([1, 2, 3, 4, 5]);
const result = await invoke<string>('upload', data, {
    headers: { Authorization: 'Bearer token123' },
});

// Receiving binary data
const imageData = await invoke<ArrayBuffer>('get_image', { path: '/photo.jpg' });

Pattern 7: Command Registration

// src-tauri/src/lib.rs
mod commands;

#[cfg_attr(mobile, tauri::mobile_entry_point)]
pub fn run() {
    tauri::Builder::default()
        .invoke_handler(tauri::generate_handler![
            commands::greet,
            commands::read_file,
            commands::download_file,
            commands::upload,
        ])
        .run(tauri::generate_context!())
        .expect("error while running tauri application");
}

Rule: ALL commands MUST be listed in a single generate_handler![] macro call. Multiple invoke_handler() calls do NOT merge.

---

Argument Name Mapping

Tauri automatically converts between JS camelCase and Rust snake_case.

Rust Parameter	JS Argument Key
file_path: String	filePath
user_name: String	userName
item_count: u32	itemCount
is_active: bool	isActive

To override this behavior:

#[tauri::command(rename_all = "snake_case")]
fn my_command(file_path: String) { }

// With rename_all = "snake_case", pass snake_case keys
await invoke('my_command', { file_path: '/tmp/file.txt' });

---

Channel vs Events

Feature	Channel	Events
Direction	Rust -> JS (response stream)	Bidirectional
Lifetime	Tied to command invocation	App lifetime
Targeting	Specific caller	Broadcast or filtered
Type safety	Generic Channel<T>	Serialized JSON
Use case	Progress, streaming data	App-wide notifications

ALWAYS use Channel<T> for progress updates and streaming data from a command. NEVER use events for command-specific streaming -- channels are scoped to the invocation.

---

Runtime Generics (Plugin Authors)

When writing commands for plugins or libraries that need to be runtime-agnostic:

use tauri::{AppHandle, Runtime, WebviewWindow};

#[tauri::command]
async fn plugin_command<R: Runtime>(
    app: AppHandle<R>,
    window: WebviewWindow<R>,
    data: String,
) -> Result<String, String> {
    Ok(format!("Processed: {}", data))
}

With the default wry feature, R resolves to Wry. This generic is only necessary for plugin/library code.

---

Reference Links

• references/methods.md -- Command macro attributes, invoke signature, Channel API
• references/examples.md -- Sync commands, async commands, binary data, channels, errors
• references/anti-patterns.md -- All command + invoke mistakes

Official Sources

• https://v2.tauri.app/develop/calling-rust/
• https://docs.rs/tauri/latest/tauri/command/index.html
• https://docs.rs/tauri/latest/tauri/ipc/struct.Channel.html
• https://www.npmjs.com/package/@tauri-apps/api