Agent skill

clap-scaffolder

Generate Clap-based Rust CLI applications with derive macros, subcommands, and modern Rust patterns. Creates production-ready Rust CLI with proper cargo structure.

View SKILL.md on GitHub Repository
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Install this agent skill to your Project

npx add-skill https://github.com/a5c-ai/babysitter/tree/main/library/specializations/cli-mcp-development/skills/clap-scaffolder

SKILL.md

Clap Scaffolder

Generate a complete Clap CLI application with Rust, derive macros, and best practices.

Capabilities

  • Generate Rust-based Clap CLI projects using derive macros
  • Create subcommand hierarchies with nested enums
  • Set up argument parsing with type validation
  • Configure shell completion generation
  • Implement colored output with anyhow error handling
  • Set up cargo workspace and build configurations

Usage

Invoke this skill when you need to:

  • Bootstrap a new CLI application using Clap
  • Create a Rust CLI with type-safe argument parsing
  • Leverage derive macros for declarative command definitions
  • Build fast, native cross-platform binaries

Inputs

Parameter Type Required Description
projectName string Yes Name of the CLI project (kebab-case)
description string Yes Short description of the CLI
commands array No List of commands to scaffold
deriveFeatures array No Clap derive features to enable
colorOutput boolean No Enable colored output (default: true)

Command Structure

json
{
  "commands": [
    {
      "name": "run",
      "description": "Run the application",
      "args": [
        { "name": "target", "help": "Target to run", "required": true }
      ],
      "options": [
        { "long": "watch", "short": "w", "help": "Watch for changes" },
        { "long": "port", "short": "p", "value_name": "PORT", "default": "3000" }
      ]
    }
  ]
}

Output Structure

<projectName>/
├── Cargo.toml
├── Cargo.lock
├── README.md
├── .gitignore
├── src/
│   ├── main.rs              # Entry point
│   ├── cli.rs               # Clap definitions
│   ├── commands/
│   │   ├── mod.rs           # Command exports
│   │   └── <command>.rs     # Individual commands
│   ├── config.rs            # Configuration
│   └── error.rs             # Error types
├── tests/
│   └── cli.rs               # CLI integration tests
└── completions/
    ├── _<projectName>       # Zsh completions
    ├── <projectName>.bash   # Bash completions
    └── <projectName>.fish   # Fish completions

Generated Code Patterns

CLI Definition (src/cli.rs)

rust
use clap::{Parser, Subcommand, Args};

#[derive(Parser)]
#[command(name = "<projectName>")]
#[command(author, version, about, long_about = None)]
pub struct Cli {
    /// Enable verbose output
    #[arg(short, long, global = true)]
    pub verbose: bool,

    /// Configuration file path
    #[arg(short, long, global = true)]
    pub config: Option<PathBuf>,

    #[command(subcommand)]
    pub command: Commands,
}

#[derive(Subcommand)]
pub enum Commands {
    /// Run the application
    Run(RunArgs),
    /// Build the project
    Build(BuildArgs),
    /// Generate shell completions
    Completions {
        /// Shell to generate completions for
        #[arg(value_enum)]
        shell: clap_complete::Shell,
    },
}

#[derive(Args)]
pub struct RunArgs {
    /// Target to run
    pub target: String,

    /// Watch for changes
    #[arg(short, long)]
    pub watch: bool,

    /// Port to use
    #[arg(short, long, default_value = "3000")]
    pub port: u16,
}

Main Entry (src/main.rs)

rust
use anyhow::Result;
use clap::Parser;
use colored::Colorize;

mod cli;
mod commands;
mod config;
mod error;

use cli::{Cli, Commands};

fn main() -> Result<()> {
    let cli = Cli::parse();

    // Setup logging based on verbosity
    if cli.verbose {
        env_logger::Builder::from_env(
            env_logger::Env::default().default_filter_or("debug")
        ).init();
    }

    match cli.command {
        Commands::Run(args) => commands::run::execute(args)?,
        Commands::Build(args) => commands::build::execute(args)?,
        Commands::Completions { shell } => {
            generate_completions(shell);
        }
    }

    Ok(())
}

Command Implementation

rust
use anyhow::Result;
use colored::Colorize;

use crate::cli::RunArgs;

pub fn execute(args: RunArgs) -> Result<()> {
    println!("{} Running target: {}", "→".blue(), args.target.green());

    if args.watch {
        println!("{} Watch mode enabled", "!".yellow());
    }

    println!("{} Listening on port {}", "✓".green(), args.port);

    Ok(())
}

Dependencies

toml
[package]
name = "<projectName>"
version = "0.1.0"
edition = "2021"

[dependencies]
clap = { version = "4.4", features = ["derive", "env"] }
clap_complete = "4.4"
anyhow = "1.0"
thiserror = "1.0"
colored = "2.0"
env_logger = "0.10"
log = "0.4"

[dev-dependencies]
assert_cmd = "2.0"
predicates = "3.0"

Workflow

  1. Validate inputs - Check project name, commands structure
  2. Create directory structure - Set up Rust project layout
  3. Generate Cargo.toml - Configure dependencies and metadata
  4. Create CLI definition - Clap derive structs
  5. Generate commands - Individual command modules
  6. Create utilities - Config, error handling
  7. Generate completions - Shell completion scripts
  8. Set up tests - CLI integration tests

Best Practices Applied

  • Derive macros for declarative definitions
  • Anyhow for error handling
  • Colored output for user feedback
  • Environment variable support
  • Built-in completion generation
  • Cross-platform compatible

References

Target Processes

  • cli-application-bootstrap
  • argument-parser-setup
  • shell-completion-scripts

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