Rust Tauri Development

Expert Tauri v2 development for building desktop applications with Rust backend and web frontend.

DECISION POINTS

IPC Pattern Selection

Data Exchange Pattern:
├─ Request/Response needed?
│  ├─ YES: Use #[tauri::command]
│  │  ├─ Sync operation? → fn command() -> Result<T, String>
│  │  └─ I/O operation? → async fn command() -> Result<T, String>
│  └─ NO: Fire-and-forget?
│     ├─ YES: Use events (emit/listen)
│     └─ Large binary data? → Use raw payload channels

State Management Pattern:
├─ Simple shared data?
│  ├─ Read-only → Arc<T>
│  ├─ Mutable + sync access → Arc<Mutex<T>>
│  └─ Mutable + async access → Arc<RwLock<T>>
├─ Database needed?
│  ├─ Simple KV → tauri-plugin-store
│  └─ Relational → tauri-plugin-sql
└─ Cross-process state? → Database or file-based

Window Architecture

Window Count Decision:
├─ Single window app?
│  └─ Use default main window only
├─ Settings/preferences needed?
│  └─ Create secondary window with restricted capabilities
├─ Background processing?
│  ├─ System tray → TrayIconBuilder + hidden main window
│  └─ No tray → Keep main window, emit progress events
└─ Multi-document interface?
    └─ Create window per document with shared state

Plugin vs Custom Code

Functionality needed:
├─ File system access?
│  ├─ Basic read/write → cargo tauri add fs
│  └─ Complex file ops → Custom commands + std::fs
├─ HTTP requests?
│  ├─ Simple → reqwest in custom commands
│  └─ Complex proxy/auth → Custom plugin
├─ Database?
│  ├─ SQLite/MySQL → cargo tauri add sql
│  └─ Custom storage → Custom plugin
└─ Platform integration?
    ├─ Notifications → cargo tauri add notification
    └─ Custom system APIs → Custom plugin

FAILURE MODES

Thread Blocking Anti-Pattern

Detection Rule: If UI freezes during Rust command execution Symptoms:

• Frontend becomes unresponsive
• Spinning cursor on macOS/Windows
• DevTools shows pending invoke() calls

Fix: Convert blocking command to async or spawn onto background thread

// BAD: Blocks the main thread
#[tauri::command]
fn heavy_computation() -> String {
    std::thread::sleep(Duration::from_secs(5)); // UI freezes
    "done".to_string()
}

// GOOD: Async command
#[tauri::command]
async fn heavy_computation() -> String {
    tokio::time::sleep(Duration::from_secs(5)).await;
    "done".to_string()
}

Serialization Panic Trap

Detection Rule: If app crashes with "failed to serialize" during invoke() Symptoms:

• App crash on specific command calls
• Serde errors in console
• Commands work with simple data but fail with complex types

Fix: Ensure all command parameters/returns implement Serialize/Deserialize

// BAD: Missing derives
struct MyData {
    field: String,
}

// GOOD: Proper derives
#[derive(Serialize, Deserialize)]
struct MyData {
    field: String,
}

Permission Escalation Error

Detection Rule: If commands fail with "not allowed" or capability errors Symptoms:

• Plugin commands return permission denied
• File operations fail unexpectedly
• "capability not granted" in logs

Fix: Add required permissions to capabilities/*.json

{
  "permissions": [
    "fs:allow-read",
    "fs:scope-app-data"  // Add specific scopes
  ]
}

State Race Condition Bug

Detection Rule: If shared state shows inconsistent values between windows Symptoms:

• Data corruption in multi-window apps
• Commands occasionally return stale data
• State updates lost intermittently

Fix: Use proper async locking (RwLock for async, Mutex for sync)

// BAD: No synchronization
static mut COUNTER: i32 = 0;

// GOOD: Proper state management
struct AppState {
    counter: Arc<Mutex<i32>>,
}

WebView Platform Divergence

Detection Rule: If layout/behavior differs dramatically between macOS and Windows Symptoms:

• CSS renders differently on different platforms
• JavaScript APIs work on one platform but not others
• Font rendering inconsistencies

Fix: Test on all platforms, use cross-platform CSS, avoid WebKit-specific features

WORKED EXAMPLES

Building a File Manager App

Scenario: Create a desktop file manager with folder tree, file operations, and progress tracking.

Step 1: Architecture Decision

• Need file system access → Use tauri-plugin-fs
• Progress updates → Use events for real-time feedback
• Multi-pane UI → Single window with multiple views

Step 2: Setup Capabilities

{
  "permissions": [
    "core:default",
    "fs:allow-read",
    "fs:allow-write", 
    "fs:allow-create",
    "fs:scope-downloads",
    "fs:scope-documents"
  ]
}

Step 3: Implement Backend Commands

#[tauri::command]
async fn list_directory(path: String, app: AppHandle) -> Result<Vec<FileEntry>, String> {
    let entries = std::fs::read_dir(&path)
        .map_err(|e| e.to_string())?
        .collect::<Result<Vec<_>, _>>()
        .map_err(|e| e.to_string())?;
    
    let mut files = Vec::new();
    for (i, entry) in entries.iter().enumerate() {
        // Emit progress for large directories
        if i % 100 == 0 {
            app.emit("scan_progress", i).unwrap();
        }
        files.push(FileEntry::from_dir_entry(entry)?);
    }
    
    app.emit("scan_complete", files.len()).unwrap();
    Ok(files)
}

#[tauri::command]
async fn copy_file(src: String, dest: String, app: AppHandle) -> Result<(), String> {
    let src_path = Path::new(&src);
    let dest_path = Path::new(&dest);
    
    // Use async file operations for large files
    let mut src_file = tokio::fs::File::open(&src_path).await
        .map_err(|e| e.to_string())?;
    let mut dest_file = tokio::fs::File::create(&dest_path).await
        .map_err(|e| e.to_string())?;
        
    // Stream copy with progress
    let file_size = src_file.metadata().await
        .map_err(|e| e.to_string())?.len();
    let mut copied = 0u64;
    
    while copied < file_size {
        let chunk_size = tokio::io::copy(&mut src_file, &mut dest_file).await
            .map_err(|e| e.to_string())?;
        copied += chunk_size;
        
        app.emit("copy_progress", (copied * 100) / file_size).unwrap();
    }
    
    Ok(())
}

What a novice would miss: Using blocking std::fs operations (freezes UI), forgetting progress events, not handling permission errors.

What an expert catches: Async file operations, progress tracking, proper error propagation, scoped capabilities.

QUALITY GATES

• All commands return Result<T, String> for proper error handling
• Async commands used for any I/O operations (file, network, database)
• Capabilities scoped to minimum required permissions per window
• App icons generated via cargo tauri icon for all required sizes
• Bundle identifier follows reverse-domain format (com.company.app)
• Event listeners properly cleaned up with unlisten() calls
• State management uses Arc<Mutex<T>> or Arc<RwLock<T>> for thread safety
• No secrets or API keys stored in frontend JavaScript code
• CSP (Content Security Policy) configured in tauri.conf.json
• Tested on both macOS and Windows for rendering consistency
• Bundle size under 50MB for simple apps (check with cargo tauri build)
• All plugins registered in lib.rs Builder chain
• Minimum OS versions specified in bundle configuration

NOT-FOR BOUNDARIES

Do NOT use for:

• Browser-only web applications → Use standard web frameworks
• Mobile applications → Use tauri-mobile (experimental) or native mobile development
• Node.js compatibility required → Use Electron instead
• Pure command-line tools → Use rust-expert skill
• Complex video/audio processing → Use native platform frameworks
• Apps requiring embedded Chromium → Use Electron

Delegate to:

• Code signing and distribution → rust-app-distribution skill
• Cross-platform UI abstractions → cross-platform-desktop skill
• Advanced TypeScript patterns → typescript-advanced-patterns skill
• Database design and optimization → database-design skill