bandersnatch

bandersnatch

Super lightweight and friendly CLI framework for Node.js.

🚧 alpha version

Features

• 🌊 Fluid syntax
• ➰ Built-in REPL
• 💬 Prompts for missing arguments
• ➡ Autocompletes arguments, options and values
• 🤯 Fully typed
• ⚡ Uses the power of yargs and inquirer

It's built-in TypeScript to provide you with some very handy type hints.

Bandersnatch is not designed to be used as a full CLI framework like oclif, and tries to minimize the assumptions made about your program to make bandersnatch easy and intuitive to work with.

Table of contents

• Getting started
  • Installation
  • Simple
  • REPL
  • Prompt
• Principles
  • Output
• API
  • program(description)
    • program.add(command)
    • program.default(command)
    • program.prompt(prompt)
    • program.withHelp()
    • program.withVersion()
    • program.run(command)
    • program.repl()
    • program.runOrRepl()
  • command(name, description)
    • command.argument(name, description, options)
    • command.option(name, description, options)
    • command.command(command)
    • command.default()
    • command.action(function)
• Bundle
• Todo
• Contributing
• License

Getting started

Installation

# Add dependency
yarn add bandersnatch

Simple

Now create a simple app concat.ts:

import { program, command } from 'bandersnatch'

const concat = command('concat', 'Concatenate input')
  .argument('input', 'List of inputs to concatenate', { variadic: true })
  .action((args) => console.log(args.input.join(', '))

program().default(concat).run()

And run with:

$ ts-node concat.ts Hello world
Hello, world

👆 Assuming you have ts-node installed.

REPL

Let's dive right into some more features. This simple app has a single default command which pretty prints JSON input. When invoked without input, it'll show an interactive prompt:

import { program, command } from 'bandersnatch'

const app = program('JSON pretty printer').default(
  command()
    .argument('json', 'Raw JSON input as string')
    .option('color', 'Enables colorized output', { type: 'boolean' })
    .action(async (args) => {
      const json = JSON.parse(args.json)
      args.color
        ? console.dir(json)
        : console.log(JSON.stringify(json, undefined, 4))
    })
)

app.runOrRepl()

And run with:

$ ts-node pretty.ts
> [0,1,1,2,3,5]
[
    0,
    1,
    1,
    2,
    3,
    5
]

Now, try typing [0,1,1,2,3,5] --c and then hit TAB. 😊

Prompt

Bandersnatch can also ask a user for input if arguments were not provided on the command line:

import { program, command } from 'bandersnatch'

const cmd = command()
  .argument('name', "What's your name?", {
    prompt: true,
  })
  .argument('question', "What's your question?", {
    prompt: true,
  })
  .action((args) => {
    console.log(`Hi ${args.name}, the answer to "${args.question}" is 42.`)
  })

program('Ask me anything').default(cmd).run()

And run with:

$ ts-node ama.ts --name Joram
? What's your question? What is the meaning of life?
Hi Joram, the answer to "What is the meaning of life?" is 42.

When you omit the --name part, the program will also prompt for it.

---

ℹ More examples in the examples directory.

Principles

In general, bandersnatch is designed to create twelve-factor apps.

Output

Programs are encouraged to use the following conventions with regards to output, based on the POSIX standard.

• When a program is designed to be used in a scripting environment and its output should be available as stdin for other programs, use stdout for printing output and stderr for diagnostic output (e.g. progress and/or error messages).
• When a program is designed to be used as a service (twelve-factor app), use stdout/stderr as a logging mechanism for informative messages/error and diagnostic messages.

Bandersnatch has no built-in method for writing to stdout/stderr. Node.js provides everything you need.

API

All methods are chainable unless the docs mention otherwise.

program(description)

Creates a new program.

• Description (string, optional) is used in --help output.

program.add(command)

Adds a command to the program.

program().add(command(...))

program.default(command)

Adds a default command to the program. Shorthand for:

program().add(command(...).default())

program.prompt(prompt)

Use this prompt prefix (string, required) when in REPL mode.

program.withHelp()

Adds help and --help to the program which displays program usage information.

program.withVersion()

Adds version and --version to the program which displays program version from package.json.

program.run(command)

Uses process.argv or passed in command (string, optional) to match and execute command. Returns promise.

program()
  .add(command(...))
  .run()

program.repl()

Start a read-eval-print loop.

program()
  .add(command(...))
  .repl()

program.runOrRepl()

Invokes run() if arguments are passed in, repl() otherwise.

program()
  .add(command(...))
  .runOrRepl()

command(name, description)

Creates a new command.

• Name (string, optional) is used to invoke a command. When not used as the default command, a name is required.
• Description (string, optional) is used in --help output.

command.argument(name, description, options)

Adds a positional argument to the command.

• Name (string, required) is used to identify the argument. Can also be an array of strings, in which case subsequent items will be treated as command aliases.
• Description (string, optional) is used in --help output.
• Options can be provided to change the behavior of the argument. Object with any of these keys:
  • optional (boolean) makes this argument optional.
  • variadic (boolean) eagerly take all remaining arguments and parse as an array. Only valid for the last argument.
  • ...

command.option(name, description, options)

Adds an option to the command.

• Name (string, required) is used to identify the option.
• Description (string, optional) is used in --help output.
• Options (OptionOptions) can be provided to change the behavior of the option. Object with any of these keys:
  • alias (string or array of strings) alias(es) for the option key.
  • ...

command.command(command)

Adds a sub-command to the command.

command.default()

Mark command as default. Default commands are executed immediately and don't require a name.

command.action(function)

Function to execute when the command is invoked. Is called with one argument: an object containing key/value pairs of parsed arguments and options.

Bundle

There are many options to bundle your application for distribution. We'll discuss a common pattern.

ℹ An example can be found in the examples/bundle directory.

Init a package.json if needed:

mkdir echo && cd echo
yarn init

Install dependencies:

yarn add bandersnatch
yarn add typescript pkg --dev

And create an example app in src/cli.ts:

import { program, command } from 'bandersnatch'

export default program()
  .withHelp()
  .default(
    command('echo', 'Echo something in the terminal')
      .argument('words', 'Say some kind words', { variadic: true })
      .action(console.log)
  )

Building your app with TypeScript is very powerful, but runtime compilation is slow so we compile the code ahead of time.

Add a tsconfig.json, similar to:

{
  "include": ["./src"],
  "compilerOptions": {
    "target": "es2017",
    "module": "commonjs",
    "lib": ["es2017"],
    "declaration": true,
    "outDir": "lib",
    "rootDir": "src",
    "strict": true,
    "allowSyntheticDefaultImports": true,
    "esModuleInterop": true,
    "moduleResolution": "node"
  }
}

Add these scripts to your package.json:

 {
   "name": "echo",
   "version": "1.0.0",
   "main": "index.js",
   "license": "MIT",
+  "scripts": {
+    "prepublishOnly": "yarn build",
+    "build": "tsc",
+  },
   "dependencies": {
     "bandersnatch": "^1.0.0-alpha.2"
   },
   "devDependencies": {
     "pkg": "^4.4.2",
     "typescript": "^3.7.3"
   }
 }

And compile now by running yarn build.

Next, we need to create a simple entry point echo.js, which can be run with node:

#!/usr/bin/env node

require('./lib/cli').default.run()

To run your app, users may want to run yarn global add echo. For this to work, we need to make a small adjustment to package.json:

 {
   "name": "echo",
   "version": "1.0.0",
-  "main": "index.js",
+  "bin": "echo.js",
+  "files": [
+    "lib"
+  ],
   "license": "MIT",
   "scripts": {
     "prepublishOnly": "yarn build",
     "build": "tsc",
   },
   "dependencies": {
     "bandersnatch": "^1.0.0-alpha.2"
   },
   "devDependencies": {
     "pkg": "^4.4.2",
     "typescript": "^3.7.3"
   }
 }

You can now npm publish.

To create a binary (your app with Node.js bundled), add this script to package.json:

 {
   "name": "echo",
   "version": "1.0.0",
   "bin": "echo.js",
   "files": [
     "lib"
   ],
   "license": "MIT",
   "scripts": {
     "prepublishOnly": "yarn build",
     "build": "tsc",
+    "bundle": "yarn build && pkg -t host ."
   },
   "dependencies": {
     "bandersnatch": "^1.0.0-alpha.2"
   },
   "devDependencies": {
     "pkg": "^4.4.2",
     "typescript": "^3.7.3"
   }
 }

👆 Omit -t host to create binaries for all platforms.

Run yarn bundle and then ./echo --help. 💪

Optionally deploy to GitHub, S3, etc. using your preferred CD method if needed.

Todo

• Better code coverage
• Choices autocompletion in REPL mode

Contributing

Contributions are very welcome. Please note this project is in a very early stage and the roadmap is a bit foggy still...

# Clone and install
git clone [e-mail]:hongaar/bandersnatch.git
cd bandersnatch
yarn

# Run an example
yarn start examples/simple.ts

Please use conventional commits.

License

Copyright (c) 2020 Joram van den Boezem. Licensed under the MIT license.

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Inspired by vorpal