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# Main API Functions
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Core programmatic interface for the React Native CLI providing functions for running the CLI, loading project configurations, and integrating with development tools.
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## Capabilities
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### CLI Execution
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Primary entry point for running the React Native CLI programmatically with optional platform-specific behavior.
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```typescript { .api }
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/**
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 * Main entry point to run the CLI with optional platform name
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 * @param platformName - Optional platform name for out-of-tree platforms (e.g., 'macos', 'windows')
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 * @returns Promise that resolves when CLI execution completes
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 * @throws CLIError when configuration loading fails or command execution encounters errors
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 */
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function run(platformName?: string): Promise<void>;
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```
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**Usage Examples:**
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```typescript
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import { run } from "@react-native-community/cli";
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// Run CLI with default behavior
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await run();
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// Run CLI with out-of-tree platform support
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await run("macos");
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```
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### Configuration Loading
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Functions for loading React Native project configuration either synchronously or asynchronously.
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```typescript { .api }
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/**
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 * Synchronously loads React Native CLI configuration
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 * @param options - Optional configuration loading options
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 * @param options.projectRoot - Project root directory path (defaults to findProjectRoot())
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 * @param options.selectedPlatform - Platform to load configuration for (e.g., 'ios', 'android')
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 * @returns Config object with project settings, platforms, and commands
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 * @throws Error if configuration cannot be loaded or project not found
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 */
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function loadConfig(options?: LoadConfigOptions): Config;
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/**
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 * Asynchronously loads React Native CLI configuration
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 * @param options - Optional configuration loading options
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 * @param options.projectRoot - Project root directory path (defaults to findProjectRoot())
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 * @param options.selectedPlatform - Platform to load configuration for (e.g., 'ios', 'android')
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 * @returns Promise resolving to Config object
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 * @throws CLIError if configuration loading fails
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 */
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function loadConfigAsync(options?: LoadConfigOptions): Promise<Config>;
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```
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**Usage Examples:**
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```typescript
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import { loadConfig, loadConfigAsync } from "@react-native-community/cli";
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// Synchronous loading
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try {
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  const config = loadConfig();
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  console.log("Project root:", config.root);
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  console.log("React Native path:", config.reactNativePath);
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} catch (error) {
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  console.log("Not in a React Native project");
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}
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// Load with custom project root
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const config = loadConfig({ projectRoot: "/path/to/project" });
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// Asynchronous loading
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const config = await loadConfigAsync();
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console.log("Available platforms:", Object.keys(config.platforms));
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// Platform-specific loading
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const iosConfig = await loadConfigAsync({ selectedPlatform: "ios" });
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console.log("iOS configuration:", iosConfig.platforms.ios);
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```
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### Development Server Middleware
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Creates middleware for Metro development server integration with WebSocket support for React Native development tools.
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```typescript { .api }
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/**
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 * Creates development server middleware for Metro bundler
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 * @param options - Middleware configuration options
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 * @param options.host - Server host (optional, defaults to localhost)
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 * @param options.port - Server port number
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 * @param options.watchFolders - Array of directories to watch for changes
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 * @returns DevServerMiddleware object with endpoints and middleware
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 */
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function createDevServerMiddleware(options: MiddlewareOptions): DevServerMiddleware;
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interface MiddlewareOptions {
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  host?: string;
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  port: number;
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  watchFolders: ReadonlyArray<string>;
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}
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interface DevServerMiddleware {
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  websocketEndpoints: {
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    '/message': any;
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    '/events': any;
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  };
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  messageSocketEndpoint: any;
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  eventsSocketEndpoint: any;
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  middleware: any;
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}
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```
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**Usage Examples:**
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```typescript
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import { createDevServerMiddleware } from "@react-native-community/cli";
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// Create development server middleware
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const middleware = createDevServerMiddleware({
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  port: 8081,
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  watchFolders: ["./src", "./node_modules"],
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});
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// Use with Express server
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app.use(middleware.middleware);
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```
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### Binary Path
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Constant providing the path to the CLI binary entry point for programmatic access.
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```typescript { .api }
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/**
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 * Path to the CLI binary entry point
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 * Resolved path to the bin.js file for programmatic execution
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 */
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const bin: string;
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```
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**Usage Examples:**
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```typescript
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import { bin } from "@react-native-community/cli";
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import { spawn } from "child_process";
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// Execute CLI binary programmatically
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const child = spawn("node", [bin, "info"], {
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  stdio: "inherit"
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});
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```
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## Types
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```typescript { .api }
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interface Config {
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  root: string;
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  reactNativePath: string;
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  reactNativeVersion: string;
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  project: ProjectConfig;
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  dependencies: Record<string, DependencyConfig>;
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  platforms: Record<string, PlatformConfig<any, any, any, any>>;
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  assets: string[];
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  commands: Command[];
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  healthChecks: [];
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}
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interface LoadConfigOptions {
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  projectRoot?: string;
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  selectedPlatform?: string;
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}
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interface ProjectConfig {
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  android?: AndroidProjectConfig;
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  ios?: IOSProjectConfig;
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  [key: string]: any;
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}
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interface MiddlewareOptions {
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  host?: string;
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  port: number;
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  watchFolders: ReadonlyArray<string>;
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}
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interface DevServerMiddleware {
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  websocketEndpoints: {
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    '/message': WebSocketServer;
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    '/events': WebSocketServer;
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  };
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  messageSocketEndpoint: MessageSocketEndpoint;
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  eventsSocketEndpoint: EventsSocketEndpoint;
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  middleware: ConnectMiddleware;
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}
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```