@lerna/diff

// Main factory function (default export)
const factory = require("@lerna/diff");

// Access DiffCommand class from factory module
const { DiffCommand } = require("@lerna/diff");

// Command module for yargs integration  
const command = require("@lerna/diff/command");

// Utility functions
const { getLastCommit } = require("@lerna/diff/lib/get-last-commit");
const { hasCommit } = require("@lerna/diff/lib/has-commit");

# Diff all packages since last release
lerna diff

# Diff specific package since last release
lerna diff my-package

# Ignore certain file patterns
lerna diff --ignore-changes "*.md" "test/**"

# Include ignored files (overrides lerna.json ignoreChanges configuration)
lerna diff --no-ignore-changes

const factory = require("@lerna/diff");
const { DiffCommand } = require("@lerna/diff");

// Create command instance using factory
const diffCommand = factory(process.argv);

// Or directly instantiate DiffCommand
const command = new DiffCommand(process.argv);
await command.runner();

/**
 * Factory function to create DiffCommand instance
 * @param argv - Process arguments array
 * @returns DiffCommand instance ready for execution
 */
function factory(argv: NodeJS.Process["argv"]): DiffCommand;

/**
 * Lerna command for showing git diff since last release
 * Extends base Command class with diff-specific functionality
 */
class DiffCommand extends Command<DiffCommandOptions> {
  /**
   * Initialize the diff command
   * - Validates package name if provided
   * - Checks repository has commits
   * - Builds git diff arguments with appropriate filters
   */
  initialize(): void;

  /**
   * Execute the git diff command
   * Spawns git diff process with constructed arguments and displays output
   * @returns Promise that resolves when git diff completes successfully or rejects on error
   */
  execute(): Promise<void>;
}

interface DiffCommandOptions extends CommandConfigOptions {
  /** Optional package name to filter diff output */
  pkgName: string;
  /** Array of glob patterns to ignore in diff output */
  ignoreChanges: string[];
}

/**
 * Yargs CommandModule for lerna diff command
 * Defines CLI interface with arguments and options
 */
const command: CommandModule = {
  command: "diff [pkgName]";
  describe: "Diff all packages or a single package since the last release";
  
  /**
   * Configure command arguments and options
   * Configures pkgName positional argument and ignore-changes option
   * Includes epilogue help text about ignoreChanges configuration
   * @param yargs - Yargs instance for configuration
   * @returns Configured yargs instance with positional and options
   */
  builder(yargs: any): any;
  
  /**
   * Handle command execution
   * Calls the factory function with parsed arguments
   * @param argv - Parsed command arguments
   * @returns Result from factory function execution
   */
  handler(argv: any): any;
};

/**
 * Get the last commit or tag for diff comparison
 * Returns latest reachable tag if available, otherwise first commit
 * @param execOpts - Child process execution options
 * @returns Commit SHA or tag reference string
 */
function getLastCommit(execOpts: ExecOpts): string;

/**
 * Check if repository has any commits
 * Used to validate diff operation is possible
 * @param opts - Child process execution options  
 * @returns True if repository has commits, false otherwise
 */
function hasCommit(opts: ExecOpts): boolean;

interface DiffCommandOptions extends CommandConfigOptions {
  /** Optional package name to filter diff output to single package */
  pkgName: string;
  /** Array of glob patterns to exclude from diff output */
  ignoreChanges: string[];
}

/**
 * Child process execution options
 * Based on @lerna/child-process ExecOpts
 */
interface ExecOpts {
  /** Working directory for command execution */
  cwd: string;
  /** Maximum buffer size for command output */
  maxBuffer?: number;
}

const { ValidationError } = require("@lerna/core");

// Example error handling
try {
  const command = new DiffCommand(argv);
  await command.runner();
} catch (error) {
  if (error instanceof ValidationError) {
    if (error.code === "ENOPKG") {
      console.error(`Package not found: ${error.message}`);
    } else if (error.code === "ENOCOMMITS") {
      console.error("No commits to diff against");
    }
  }
}