alwaysCLI

A framework for building command-line interfaces (CLIs) in Node.js. This package includes runtime JavaScript files suitable for Node.js >=8 as well as the corresponding TypeScript type declarations.

Usage

npm install @alwaysai/always-cli

In an alwaysCLI CLI, commands are organized into a tree. Each "leaf" represents an action whereas "branches" collect and organize leaves. For example, in the command alwaysai user logIn, alwaysai is the "root" command, user is a branch of commands related to user authentication and logIn is the specific action (leaf command). Your CLI need not have branches. Here is a simple CLI that has a leaf as its root:

import {
  createCli,
  createLeaf,
  createFlagInput,
  createNumberArrayInput,
  runAndExit,
} from '@alwaysai/always-cli';

const root = createLeaf({
  name: 'multiply',
  description: 'Multiply numbers and print the result',
  args: createNumberArrayInput({ required: true }),
  options: {
    squared: createFlagInput({
      description: 'Square the result before printing it',
    }),
  },
  action(args, { squared }) {
    const multiplied = args.reduce((a, b) => a * b, 1);
    if (squared) {
      return multiplied * multiplied;
    }
    return multiplied;
  },
});

export const cli = createCli(root);

if (require.main === module) {
  runAndExit(cli, ...process.argv.slice(2));
}

cli is a function that takes command-line arguments (strings) as input and returns a Promise representing the execution of the arguments. We export cli so that we can unit test it like so. The if (require.main === module) snippet near the end is idiomatic Node.js for "if this module is the entrypoint", which is true when you do node readme.ts, but not when you do require('./readme.ts'), for example in a unit test. The runAndExit helper just runs the provided function with the provided arguments, console.logs the result, then process.exit's.

Here's how that behaves as a CLI. In this case since the args property of the leaf has required set to true, alwaysCLI will print the top-level command usage and an error message if no positional arguments are provided:

$ multiply
Usage: multiply <num0> [...] [<options>]

   Multiply numbers and print the result

Options:

   [--squared] : Square the result before printing it

Error: "<num0> [...]": Value is required

With arguments:

$ multiply 1 2 3
6
$ multiply 1 2 3 --squared
36 

More generally the usage of an alwaysCLI CLI is:

<program> [<branch0> ...] [leaf] [<arg0> [...]] [--option0 <val0> ...] [...]

To invoke an action the user provides (in order):

• zero or more branch names
• a leaf name
• zero or more positional args
• zero or more "options" (inputs of the form --foo bar)

API

Input<T, U>

TODO

createLeaf({name, description?, args?, options?, action, hidden?, version?})

A factory for creating "action" commands. Returns the newly-created leaf.

name

If this "leaf" is a subcommand, name is the string that the user will pass as the "subcommand" argument to invoke this action. If this "leaf" is the root command, name should be the CLI's name.

description

(Optional) A string that will be included in Usage: if present.

args

(Optional) An Input for

options

(Optional) An object of named Inputs, for example:

const options = {
  path: createStringInput({
    description: 'An absolute or relative path',
  }),
}

The args and options properties define how the command-line arguments get parsed and transformed before being passed into the action function.

action(args, options)

The function that defines your command logic. action can return a value synchronously like in the "multiply" example above, or it can be an async function that returns a Promise. If action returns/resolves a value, that value is console.logged before the CLI exits. If action throws/rejects, the exception is console.logged before the CLI exits. That means that if you don't want the user to see a stack trace, your action should throw a string instead of an Error object. The type of the args argument received by action is derived by the args property of the leaf. Similarly, the options argument type is derived from leaf.options.

hidden

(Optional) boolean

version

(Optional) string. If provided, this string will be printed when the user does cli --version or cli -v. If this value is not provided, alwaysCLI will attempt to find a version string in your package.json file.

createBranch({name, description, subcommands, hidden?})

A factory function similar to createLeaf. Returns the newly-created Branch object.

name

If this "branch" is not the root command, name is the string that the user will pass as the "subcommand" argument to invoke actions in this part of the command tree. If this "branch" command is the root command, name should be the CLI's name.

description

(Optional) A string that will be included in Usage: if present.

subcommands

An array of Branch and/or Leaf objects.

hidden

(Optional) boolean

createCli(root)

Returns a function of the form (...args: string[]) => Promise<any> that can be invoked as e.g. cli('foo', 'bar') for unit tests or as cli(process.argv.slice(2)) in an executable CLI script.

root

A Leaf or Branch

More information

This library has a couple dozen unit tests with >90% coverage. If you want to see more examples of how things works, check out the .test.ts files in the src directory. Also check out src/examples. If you encounter any bugs or have any questions or feature requests, please don't hesitate to file an issue or submit a pull request on this project's repository on GitHub.

License

MIT © alwaysAI, Inc.