!Tauris demonstrated in a terminal

---

Table of contents

- Quickstart
- Features
- Installation
- API Reference
- Contributing
- License

⚡️ Quickstart

``js
import { Command } from "tauris";

const mycommand = new Command("mycommand")
.option("v", {
alias: "version",
description: "Display the version number",
type: "boolean",
})
.demandArgument();

const options = mycommand.parse(process.argv.slice(2));

if (options?.v) console.log("versin 1.0.0");
`

🎨 Features

- 🍃 Lightweight: Weighs in just under 7.5kb
- ⚡️ Typescript Compatible: Provides typings out of the box
- ✨ Clean User Interface: Render friendly, scannable help menus

🚀 Installation

`bash
$ npm i tauris # or: yarn add tauris
`

🧑‍💻 API Reference

new Command(name: string)

Creates a new command or subcommand:

`js
import { Command } from "tauris";

const mycommand = new Command("mycommand");
`

$3

A command can be configured with its "configuration methods" (.usage, .describe, .option, etc.). These methods will apply a configuration change to the command and then return the command they were called on to allow chaining them together. For example:

`js
mycommand.describe("Description").usage("mycommand ");
`

will first add a description, then set the usage string, and then return the command.

$3

- You can override the usage string using .usage(usage: string).
- You can give your command a description using .description(description: string) (This description will be displayed in the help menu of the parent command, so if your command is not a subcommand, this option isn't useful.).
- .header(header: string) adds a string that displays above the help message.

$3

You can add an option to a command using .option(nams: string[, options: CLIOptionOptions]):

`js
mycommand.option(
// Option name. If you want your option to have a short and long name, like
// "-v" and "--version", use the short one here and make the longer one an
// alias.
"v",
{
// A single alias or list of alias names for the option
alias: "version",
// A short description to display in the help menu
description: "Display version number",
// Data type of the option (defaults to 'text')
type: "boolean",
}
);
`

The optional type option allows you to set one of three data types for your option: boolean, number or text (default is text). These will treat the given value differently:

- Boolean will treat the option as a flag which is true if the option is present and false if it isn't, therefore

$3

If you need a command to pass options down to its subcommands, use .rootOption. This method takes the same arguments as .option. By using .clearRoot([names: string | string[]]), you can remove root options from a subcommand and its subcommands:

`js
// Now, mysubcommand no longer has the -s root option, but other
// subcommands still do:
mysubcommand.clearRoot("s");
`

$3

You can add any command as a subcommand by running parentCommand.command(subcommand) (This adds subcommand as a subcommand of parentCommand).

> Note: Setting a command as a subcommand mutates said subcommand. Therefore, the same subcommand instance cannot be added as a subcommand to multiple different commands. Use command.copy() to create a copy of the command in order to set multiple subcommands.

You can get any command's parent command using command.parent or the root command using .root() (In git remote add origin, add is the deepest subcommand, its parent is remote and the root command is git. Note that the root command is always the same no matter what command we start at (git.root() === remote.root() === add.root() === git)).

Every subcommand needs a handler: The handler is the code that runs when the subcommand is invoked. You can add the handler using .handler(async function handler(args) {}):

`js
mysubcommand.handler(async function (args) {
console.log("You ran mysubcommand!");
});
`

Inside the handler function, this is the command the handler was applied to (remember: this doesn't work in arrow functions!) and args are all the options passed to the subcommand. Note that tauris only invokes the handler of the deepest subcommand, i.e. if the command rootcommand has a subcommand foo that has a sub-subcommand bar and the user runs rootcommand foo bar, only the handler for bar will be invoked.

Note that handlers _may_ be asynchronous, but they don't have to.

$3

When writing CLIs, it's often useful to be able to exit prematurely from a program or control the exit code it returns. For this, the process.exit() function is commonly used. However, this approach has its issues: We can only call .parse() once, then the handler _may_ force the program to exit, but there's no way to know for sure.

Instead, when you need to exit, simply return the desired exit code from your handler. Usually, this will immediately cause your program to exit, but it can also be surpressed by passing noExit: true to .parse (see parsing arguments).

$3

- .demandArgument() – Show the help menu if the command is called without arguments
- .noHelp() – Disable the help menu entirely

#### Internationalisation

The help menu (see screenshot at top) contains some template text like "Usage:" and "Options:", which is in english by default. If your tool is intended for users more familiar with another language, you can use the .language() method:

`js
// Apply german translation
mycommand.language({
"Usage:": "Nutzung:",
"Commands:": "Befehle:",
"Root Options:": "Root-Optionen:",
"Options:": "Optionen:",
"Display this help message": "Diese Hilfsinformationen anzeigen",
});
`

For a different language, simply replace the strings on the right with the correct translation for the desired language. The language is passed down to all subcommands.

$3

Once you've used the above methods to describe your command, run .parse() to parse command line arguments:

`js
const command = new Command("command")
.option('v', {alias: 'version', type: 'boolean', description: ''});
.option('o', {alias: 'output', type: 'text', description: ''});

command.parse([]);
command.parse(['-v']); // { v: true }
command.parse(['--version']); // { v: true }
command.parse(['-o']); // { o: undefined }
command.parse(['-o', 'output.txt']); // { o: 'output.txt' }
command.parse(['--output', 'output.txt']); // { o: 'output.txt' }

// Parse arguments from argv
command.parse(process.argv.slice(2));
`

To parse the arguments given to the script when it was run, use .parse(process.argv.slice(2)) rather than .parse(process.argv). This is because process argv always begins with the path to the nodejs binary running the script, then the path to the script, and only after that the actual arguments.

If, while parsing the arguments, tauris detects that a subcommand is being invoked, it will automatically invoke the subcommand's handler and return a promise that resolves to the subcommand's exit code once the handler is done. If tauris detects invalid input, it will return false.

The .parse method additionally takes an options argument:

`js
command.parse([], {
noExit: true,
noPromise: true
})
`

Set noExit to make the exit method a no-op (see exiting from subcommands) and instead return the exit code (if a subcommand is invoked).

Set noPromise to return false and let the handler run in the background rather than returning a promise (if a subcommand is invoked)

🛸 Contributing

You can contribute to tauris` in many ways like creating new features, fixing buges and improving documentation or examples. Find more information in CONTRIBUTING.md

⚖️ License

Copyright © 2020-present – John Sarjeant