Building multi command CLI tools should be easy. We've written @enzsft/cli to ensure you can get up and running writing one as quickly as possible. It handles executing commands, parsing options and validating options.

Motivation 🧐

A pain building CLI tools with existing libraries has always been the inability to fully test the commands you configure as a user would use them.

So our biggest goal building this library was to provide a super easy way to test commands as a whole, not just the handler functions, and in a way that matches how a user would. We have a section on testing your commands in this README!

We also wanted to provide a codebase that leveraging modern JavaScript and provides simpler types than alternatives via TypeScript.

Getting started 🏎

Getting up and running is fast! ⚡️

1. Install the package:

yarn add @enzsft/cli

# or

npm install @enzsft/cli

2. Create a new file and paste the following example:

// index.js

import { createCli, createBooleanOption } from "@enzsft/cli";

const echoCommand = {
  name: "echo",
  description: "Echos back string values. Optionally capitalize them.",
  options: [
    createBooleanOption({
      name: "capitalize",
      altName: "c",
      description: "Capitalize all values.",
      required: false,
      defaultValue: false,
    }),
  ],
  handler: (values, options) => {
    for (const value of values) {
      console.log(options.capitalize ? value.toUpperCase() : value);
    }

    return Promise.resolve();
  },
};

const cli = createCli({
  name: "example",
  description: "Example CLI tool build with @enzsft/cli",
  commands: [echoCommand],
  version: "1.0.0",
});

cli.start(process.argv).catch(() => process.exit(1));

3. Run the tool!

node index.js --help
#
# Echos back string values. Optionally capitalize them.
#
# Options:
#
#     --help, --h       Display tool help.
#     --version, --v    Display tool version.
#
# Usage: example [command] [options...]
#
# Commands:
#
#     echo    Echos back string values. Optionally capitalize them.
#
#             --capitalize, --c    Capitalize all values.

node index.js echo hello
# hello

node index.js echo --capitalize hello
# HELLO

API 🌳

Create a new CLI

import { createCli } from "@enzsft/cli";

const cli = createCli({
  name: "", // Should match the executable name so `--help` docs are correct.
  description: "",
  commands: [],
  version: require("./package.json").version, // Useful to use your package version
});

Start the CLI

cli
  .start(process.argv) // Commands and options are parsed from `argv`
  .catch(() => process.exit(1)); // Prevent UnhandledPromiseRejection from node

Creating commands

const command = {
  name: "", // If 2 commands names match, the command registered first will win
  description: "",
  options: [],
  handler: (values, options) => Promise.resolve(), // Should always return a promise
};

Creating options

import {
  createBooleanOption,
  createNumberOption,
  createStringOption,
} from "@enzsft/cli";

const options = [
  createBooleanOption({
    name: "bool",
    altName: "b",
    description: "Some boolean option.",
    required: false,
    defaultValue: false,
  }),
  createNumberOption({
    name: "number",
    altName: "n",
    description: "Some number option.",
    required: false,
    defaultValue: 1,
  }),
  createStringOption({
    name: "string",
    altName: "b",
    description: "Some string option.",
    required: false,
    defaultValue: "hello world",
  }),
];

Options are parsed from argv and then injected into the executing command's handler function. When they are injected they are converted into the correct type.

Built with TypeScript with 💖

TypeScript type definitions are bundled in with the module. No need to install an additional module for type definitions.

Testing your commands 🧪

All examples use Jest ✌️

This library was built with testing in mind. We believe in testing your commands as closely to how a user would use them as possible!

Take the following command:

import { createBooleanOption } from "@enzsft/cli";

export const createEchoCommand = logger => ({
  name: "echo",
  description: "Echos back string values.",
  options: [
    createBooleanOption({
      name: "capitalize",
      altName: "c",
      description: "Capitalize all values.",
      required: false,
      defaultValue: false,
    }),
  ],
  handler: (values, options) => {
    for (const value of values) {
      logger.log(options.capitalize ? value.toUpperCase() : value);
    }

    return Promise.resolve();
  },
});

We want to ensure the commands options are wired up correctly when testing. This means we can't just run the handler in our tests and inject the options like:

describe("BAD TESTS... In our opinion 😅", () => {
  it("should echo the values", async () => {
    const mockLogger = { log: jest.fn() };
    const command = createEchoCommand(mockLogger);

    const values = ["one", "two"];
    await command.handler(values, { capitalize: false });

    expect(mockLogger.log).toHaveBeenCalledTimes(2);
    values.forEach((x, i) => {
      expect(mockLogger.log).toHaveBeenNthCalledWith(i + 1, x);
    });
  });

  it("should echo the values capitalized", async () => {
    const mockLogger = { log: jest.fn() };
    const command = createEchoCommand(mockLogger);

    const values = ["one", "two"];
    await command.handler(values, { capitalize: true });

    expect(mockLogger.log).toHaveBeenCalledTimes(2);
    values.forEach((x, i) => {
      expect(mockLogger.log).toHaveBeenNthCalledWith(i + 1, x.toUpperCase());
    });
  });
});

Ok, so the above tests aren't "BAD TESTS"! They assert all the behaviour of the handler well enough. They'll even result in 100% test coverage! However... We injected a perfect options object each time. These tests would still pass if we changed the alternative name for the capitalize option from "c" to "b".

In order to combat this we provide a simple test utility function, buildArgv. This allows us to invoke the command just how a user does! With a command string!

import { createCli } from "@enzsft/cli";
import { buildArgv } from "@enzsft/cli/test-utils";

describe("BETTER TESTS... In our opinion 😁", () => {
  it("should echo the values", async () => {
    const mockLogger = { log: jest.fn() };
    const command = createEchoCommand(mockLogger);
    const cli = createCli({
      commands: [command],
      description,
      name,
      version: "1.0.0",
    });

    // Invoke the command via its name and
    // pass values like you would in the terminal
    const values = ["one", "two"];
    await cli.start(buildArgv(`echo ${values.join(" ")}`));

    expect(mockLogger.log).toHaveBeenCalledTimes(2);
    values.forEach((x, i) => {
      expect(mockLogger.log).toHaveBeenNthCalledWith(i + 1, x);
    });
  });

  it("should echo the values capitalized (name)", async () => {
    const mockLogger = { log: jest.fn() };
    const command = createEchoCommand(mockLogger);
    const cli = createCli({
      commands: [command],
      description,
      name,
      version: "1.0.0",
    });

    // Yay we can pass the option in like a user would now!
    const values = ["one", "two"];
    await cli.start(buildArgv(`echo --capitalize ${values.join(" ")}`));

    expect(mockLogger.log).toHaveBeenCalledTimes(2);
    values.forEach((x, i) => {
      expect(mockLogger.log).toHaveBeenNthCalledWith(i + 1, x.toUpperCase());
    });
  });

  it("should echo the values capitalized (alternative name)", async () => {
    const mockLogger = { log: jest.fn() };
    const command = createEchoCommand(mockLogger);
    const cli = createCli({
      commands: [command],
      description,
      name,
      version: "1.0.0",
    });

    // Yay we can pass the option in like a user would now!
    const values = ["one", "two"];
    await cli.start(buildArgv(`echo -c ${values.join(" ")}`));

    expect(mockLogger.log).toHaveBeenCalledTimes(2);
    values.forEach((x, i) => {
      expect(mockLogger.log).toHaveBeenNthCalledWith(i + 1, x.toUpperCase());
    });
  });
});

Alternatives 😽

Our favourites are Yargs and Commander. They're awesome, check them out! This library was written mainly the solve the testing issue explained above.