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Stage 2: CLI Development

In this stage, you'll master the development of professional command-line applications using TypeScript. This stage applies the type safety and architectural principles from Stage 1 to build robust, production-ready CLI tools with comprehensive system integration.

Professional Learning Objectives​

Upon completion of this stage, you will demonstrate proficiency in:

Advanced CLI Architecture:

  • Designing intuitive, user-friendly command-line interfaces with Commander.js or Yargs
  • Implementing complex command hierarchies and subcommand structures
  • Creating responsive, well-designed user interactions with Inquirer.js
  • Building configurable applications with robust option and argument parsing

System Integration & Operations:

  • Comprehensive file system operations with proper error handling and validation
  • Process management and inter-process communication patterns
  • Environment variable and configuration file management
  • Cross-platform compatibility and path resolution

Professional Tool Development:

  • Publishing npm packages with proper versioning and documentation
  • Implementing global installation and execution patterns
  • Creating interactive command-line experiences with progress indicators
  • Developing testable, maintainable CLI applications with dependency injection

Type Safety in CLI Context:

  • Strongly-typed argument and option validation
  • Type-safe configuration object design
  • Error handling patterns specific to command-line applications
  • Integration of TypeScript's advanced types in CLI tool architecture

Industry-Standard Practices​

This stage emphasizes professional development patterns:

  • User Experience: Creating intuitive, well-documented command-line interfaces
  • Performance: Optimizing CLI tool startup time and execution efficiency
  • Reliability: Implementing robust error handling and graceful degradation
  • Maintainability: Following architectural patterns that support long-term maintenance

Stage Structure​

The CLI Development stage is organized into comprehensive modules:

  1. Basic CLI Tools: Simple command-line applications with argument parsing
  2. Interactive CLIs: User input, prompts, and visual feedback systems
  3. File Operations: System-level file and directory manipulation
  4. Configuration Management: Environment variables, config files, and option handling
  5. Package Publishing: Creating and publishing npm packages for CLI tools
  6. Advanced CLI Patterns: Complex command hierarchies and multi-step operations

Prerequisites​

Before beginning this stage, ensure you have:

  • Completed Stage 1: TypeScript Foundations with strong understanding of type systems
  • Node.js 18+ and npm 9+ installed
  • Understanding of basic file system operations in Node.js
  • Familiarity with package.json configuration and npm scripts

Professional Development Standards​

All CLI applications developed in this stage must adhere to professional standards:

  • Strict TypeScript compilation with all strict flags enabled
  • Comprehensive input validation and error handling
  • Proper documentation and help text generation
  • Unit and integration tests with minimum 80% coverage
  • Adherence to established CLI design patterns and conventions

Getting Started​

Begin with basic CLI exercises and progressively build more complex tools. Each exercise increases in complexity while maintaining professional quality standards. Focus on creating tools that follow industry best practices for CLI design and implementation.

The exercises in this stage bridge the gap between foundational TypeScript knowledge and practical, real-world tool development.

Continue with the exercises to develop your first professional CLI application.