commander-register

Extends commander.js with a fastify-like plugin register api.

Features:

• type safety: plugins that extend the command instance are supported.
• lightweight: no dependencies needed.
• familiar: similar api to fastify's register api

Example:

import { Command } from "commander";
import "commander-register/patch";

new Command()
  .option("-c, --compress")
  .command("sub-command")
  .register(prettyErrors)
  .register(setMeta)
  .register(logger)
  .action(() => {
    // noop
  })
  .parse();

See ./examples/plugins.mjs

Installation

npm install commander-register
pnpm install commander-register
yarn add commander-register

Setup

Import commander-register/patch once at the entry point of your app. It patches Command.prototype with the register method. All Command instances (including those created via createCommand) will have register available.

import "commander-register/patch";
import { Command, program } from "commander";

program.register(prettyErrorsPlugin).parse();

const command = new Command();
command.register(loggerPlugin);

Applying the patch using node --import

You can also apply the patch globally using Node's --import flag:

node --import commander-register/patch your-app.js

Plugins

Use command.register(plugin) to modify command behavior. plugin is a function that receives the Command object.

Example:

program.register(prettyErrors).parse();

function prettyErrors(command) {
  command.configureOutput({
    /* snip */
  });
}

Extending command instance with more functionality

Return the instance from the plugin to let TypeScript infer the newly added methods:

program.register(helloWorldPlugin).helloWorld().parse();

function helloWorldPlugin(command) {
  return Object.assign(command, {
    helloWorld() {
      console.log("Hello World");
      return this;
    },
  });
}

defineCommanderPlugin

Use the defineCommanderPlugin helper to ensure type safety when creating plugins:

import { defineCommanderPlugin } from "commander-register";

export const prettyErrors = defineCommanderPlugin((command) => {
  command.configureOutput({
    /* snip */
  });
});

Resources

• https://github.com/tj/commander.js/issues/2505 - Plugin API discussion in commander.js
• https://github.com/tj/commander.js/pull/2503 - Pull request adding this plugin to commander.js codebase.