Unjs Citty Agent Skill

unjs/citty citty

Version: 0.2.1 (yesterday)

Tags: latest: 0.2.1 (yesterday)

References: package.json • README • GitHub Issues • Releases

Search

Use npx -y skilld search instead of grepping .skilld/ directories — hybrid semantic + keyword search across all indexed docs, issues, and releases.

npx -y skilld search "query" -p citty
npx -y skilld search "issues:error handling" -p citty
npx -y skilld search "releases:deprecated" -p citty

Filters: docs:, issues:, releases: prefix narrows by source type.

API Changes

⚠️ ESM-only — v0.2.0 ships ESM only, require('citty') no longer works source

⚠️ node:util.parseArgs internally — v0.2.0 replaced custom parser with Node.js native util.parseArgs, edge cases around arg parsing may differ from v0.1.x source

⚠️ Optional args type T | undefined — v0.2.0 improved type inference: args without required: true or default now correctly type as T | undefined instead of T source

⚠️ --no- negation conditionally printed — v0.2.0 only shows --no-<flag> in usage when negativeDescription is set; previously always shown source

✨ type: "enum" — new arg type in v0.2.0, requires options: string] array. Typed as union of options values [source

args: {
  color: {
    type: "enum",
    options: ["red", "blue", "green"] as const,
    description: "Pick a color",
  },
}
// args.color typed as "red" | "blue" | "green" | undefined

✨ meta.hidden — v0.2.0, hides a subcommand from usage/help output source

✨ negativeDescription — v0.2.0, on boolean args, sets description for the --no-<flag> variant in usage source

✨ cleanup hook — v0.1.4, runs after run() completes (mirror of setup) source

✨ createMain(cmd) — v0.1.4, returns a reusable (opts?) => Promise<void> wrapper around runMain source

✨ --version flag — v0.1.4, auto-handled when meta.version is set source

✨ runMain({ showUsage }) — v0.1.5, accepts custom showUsage function to override default help rendering source

⚠️ --no- propagation fix — v0.2.1, --no-<flag> now correctly negates aliases too (was broken in v0.2.0) source

Best Practices

✅ Use setup and cleanup hooks for lifecycle management — undocumented in README but fully supported; cleanup runs in finally block so it executes even on errors source

defineCommand({
  args: { db: { type: "string", default: "mydb" } },
  async setup({ args }) { await connectDb(args.db) },
  async cleanup() { await disconnectDb() },
  async run({ args }) { /* db is connected */ },
})

✅ Use enum type with options for constrained values — validates input and shows allowed values in usage/error messages (v0.2.0+) source

args: {
  format: {
    type: "enum",
    options: ["json", "yaml", "toml"],
    default: "json",
    description: "Output format",
  },
}

✅ Use meta.hidden: true to hide subcommands from usage output — keeps internal/debug commands accessible but invisible (v0.2.0+) source

subCommands: {
  debug: () => defineCommand({ meta: { name: "debug", hidden: true }, run() {} }),
}

✅ Make subCommands values lazy via arrow functions — citty resolves them with resolveValue(), enabling code-splitting and faster startup source

subCommands: {
  deploy: () => import("./commands/deploy").then(m => m.default),
  build: () => import("./commands/build").then(m => m.default),
}

✅ Use negativeDescription on boolean args that default to true — citty auto-generates --no-* flags with separate help text (v0.2.0+) source

args: {
  color: {
    type: "boolean",
    default: true,
    description: "Colorize output",
    negativeDescription: "Disable colored output",
  },
}

✅ Pass custom showUsage to runMain for branded help screens — citty calls your function instead of the built-in one for --help and error display source

runMain(cmd, {
  showUsage: async (cmd, parent) => {
    console.log(await renderUsage(cmd, parent))
    console.log("\nDocs: https://example.com/docs")
  },
})

✅ Arg names auto-alias between camelCase and kebab-case — defining outputDir auto-creates --output-dir and vice versa; don't add redundant aliases source

✅ --version only works as the sole argument — citty checks rawArgs.length === 1 && rawArgs0] === "--version", so --version --verbose won't trigger it; set meta.version on the root command [source

✅ Use runCommand over runMain for programmatic invocation — runMain calls process.exit(1) on errors and handles --help/--version; runCommand returns { result } and lets errors propagate source

const { result } = await runCommand(cmd, { rawArgs: ["build", "--prod"] })

✅ Avoid positional args on commands with subcommands — if a positional value matches a subcommand name, citty routes to the subcommand instead of using it as the arg value source