node_modules/meow/readme.md - devtools/devtools-frontend - Git at Google

 # meow

 > CLI app helper

 ![](meow.gif)

 ## Features

 - Parses arguments
 - Converts flags to [camelCase](https://github.com/sindresorhus/camelcase)
 - Negates flags when using the `--no-` prefix
 - Outputs version when `--version`
 - Outputs description and supplied help text when `--help`
 - Makes unhandled rejected promises [fail hard](https://github.com/sindresorhus/hard-rejection) instead of the default silent fail
 - Sets the process title to the binary name defined in package.json

 ## Install

 ```
 $ npm install meow
 ```

 ## Usage

 ```
 $ ./foo-app.js unicorns --rainbow
 ```

 **CommonJS**

 ```js
 #!/usr/bin/env node
 'use strict';
 const meow = require('meow');
 const foo = require('.');

 const cli = meow(`
 	Usage
 	  $ foo <input>

 	Options
 	  --rainbow, -r  Include a rainbow

 	Examples
 	  $ foo unicorns --rainbow
 	  🌈 unicorns 🌈
 `, {
 	flags: {
 		rainbow: {
 			type: 'boolean',
 			alias: 'r'
 		}
 	}
 });
 /*
 {
 	input: ['unicorns'],
 	flags: {rainbow: true},
 	...
 }
 */

 foo(cli.input[0], cli.flags);
 ```

 **ES Modules**

 ```js
 #!/usr/bin/env node
 import {createRequire} from 'module';
 import foo from './lib/index.js';

 const meow = createRequire(import.meta.url)('meow');

 const cli = meow(`
 	Usage
 	  $ foo <input>

 	Options
 	  --rainbow, -r  Include a rainbow

 	Examples
 	  $ foo unicorns --rainbow
 	  🌈 unicorns 🌈
 `, {
 	flags: {
 		rainbow: {
 			type: 'boolean',
 			alias: 'r'
 		}
 	}
 });
 /*
 {
 	input: ['unicorns'],
 	flags: {rainbow: true},
 	...
 }
 */

 foo(cli.input[0], cli.flags);
 ```

 ## API

 ### meow(helpText, options?)
 ### meow(options)

 Returns an `object` with:

 - `input` *(Array)* - Non-flag arguments
 - `flags` *(Object)* - Flags converted to camelCase excluding aliases
 - `unnormalizedFlags` *(Object)* - Flags converted to camelCase including aliases
 - `pkg` *(Object)* - The `package.json` object
 - `help` *(string)* - The help text used with `--help`
 - `showHelp([exitCode=2])` *(Function)* - Show the help text and exit with `exitCode`
 - `showVersion()` *(Function)* - Show the version text and exit

 #### helpText

 Type: `string`

 Shortcut for the `help` option.

 #### options

 Type: `object`

 ##### flags

 Type: `object`

 Define argument flags.

 The key is the flag name in camel-case and the value is an object with any of:

 - `type`: Type of value. (Possible values: `string` `boolean` `number`)
 - `alias`: Usually used to define a short flag alias.
 - `default`: Default value when the flag is not specified.
 - `isRequired`: Determine if the flag is required. (Default: false)
 	- If it's only known at runtime whether the flag is required or not, you can pass a `Function` instead of a `boolean`, which based on the given flags and other non-flag arguments, should decide if the flag is required. Two arguments are passed to the function:
 	- The first argument is the **flags** object, which contains the flags converted to camel-case excluding aliases.
 	- The second argument is the **input** string array, which contains the non-flag arguments.
 	- The function should return a `boolean`, true if the flag is required, otherwise false.
 - `isMultiple`: Indicates a flag can be set multiple times. Values are turned into an array. (Default: false)
 	- Multiple values are provided by specifying the flag multiple times, for example, `$ foo -u rainbow -u cat`. Space- or comma-separated values are [currently *not* supported](https://github.com/sindresorhus/meow/issues/164).

 Note that flags are always defined using a camel-case key (`myKey`), but will match arguments in kebab-case (`--my-key`).

 Example:

 ```js
 flags: {
 	unicorn: {
 		type: 'string',
 		alias: 'u',
 		default: ['rainbow', 'cat'],
 		isMultiple: true,
 		isRequired: (flags, input) => {
 			if (flags.otherFlag) {
 				return true;
 			}

 			return false;
 		}
 	}
 }
 ```

 ##### description

 Type: `string | boolean`\
 Default: The package.json `"description"` property

 Description to show above the help text.

 Set it to `false` to disable it altogether.

 ##### help

 Type: `string | boolean`

 The help text you want shown.

 The input is reindented and starting/ending newlines are trimmed which means you can use a [template literal](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/template_strings) without having to care about using the correct amount of indent.

 The description will be shown above your help text automatically.

 ##### version

 Type: `string | boolean`\
 Default: The package.json `"version"` property

 Set a custom version output.

 ##### autoHelp

 Type: `boolean`\
 Default: `true`

 Automatically show the help text when the `--help` flag is present. Useful to set this value to `false` when a CLI manages child CLIs with their own help text.

 This option is only considered when there is only one argument in `process.argv`.

 ##### autoVersion

 Type: `boolean`\
 Default: `true`

 Automatically show the version text when the `--version` flag is present. Useful to set this value to `false` when a CLI manages child CLIs with their own version text.

  This option is only considered when there is only one argument in `process.argv`.

 ##### pkg

 Type: `object`\
 Default: Closest package.json upwards

 package.json as an `object`.

 *You most likely don't need this option.*

 ##### argv

 Type: `string[]`\
 Default: `process.argv.slice(2)`

 Custom arguments object.

 ##### inferType

 Type: `boolean`\
 Default: `false`

 Infer the argument type.

 By default, the argument `5` in `$ foo 5` becomes a string. Enabling this would infer it as a number.

 ##### booleanDefault

 Type: `boolean | null | undefined`\
 Default: `false`

 Value of `boolean` flags not defined in `argv`.

 If set to `undefined`, the flags not defined in `argv` will be excluded from the result.
 The `default` value set in `boolean` flags take precedence over `booleanDefault`.

 _Note: If used in conjunction with `isMultiple`, the default flag value is set to `[]`._

 __Caution: Explicitly specifying `undefined` for `booleanDefault` has different meaning from omitting key itself.__

 Example:

 ```js
 const meow = require('meow');

 const cli = meow(`
 	Usage
 	  $ foo

 	Options
 	  --rainbow, -r  Include a rainbow
 	  --unicorn, -u  Include a unicorn
 	  --no-sparkles  Exclude sparkles

 	Examples
 	  $ foo
 	  🌈 unicorns✨🌈
 `, {
 	booleanDefault: undefined,
 	flags: {
 		rainbow: {
 			type: 'boolean',
 			default: true,
 			alias: 'r'
 		},
 		unicorn: {
 			type: 'boolean',
 			default: false,
 			alias: 'u'
 		},
 		cake: {
 			type: 'boolean',
 			alias: 'c'
 		},
 		sparkles: {
 			type: 'boolean',
 			default: true
 		}
 	}
 });
 /*
 {
 	flags: {
 		rainbow: true,
 		unicorn: false,
 		sparkles: true
 	},
 	unnormalizedFlags: {
 		rainbow: true,
 		r: true,
 		unicorn: false,
 		u: false,
 		sparkles: true
 	},
 	…
 }
 */
 ```

 ##### hardRejection

 Type: `boolean`\
 Default: `true`

 Whether to use [`hard-rejection`](https://github.com/sindresorhus/hard-rejection) or not. Disabling this can be useful if you need to handle `process.on('unhandledRejection')` yourself.

 #### allowUnknownFlags

 Type `boolean`\
 Default: `true`

 Whether to allow unknown flags or not.

 ## Promises

 Meow will make unhandled rejected promises [fail hard](https://github.com/sindresorhus/hard-rejection) instead of the default silent fail. Meaning you don't have to manually `.catch()` promises used in your CLI.

 ## Tips

 See [`chalk`](https://github.com/chalk/chalk) if you want to colorize the terminal output.

 See [`get-stdin`](https://github.com/sindresorhus/get-stdin) if you want to accept input from stdin.

 See [`conf`](https://github.com/sindresorhus/conf) if you need to persist some data.

 See [`update-notifier`](https://github.com/yeoman/update-notifier) if you want update notifications.

 [More useful CLI utilities…](https://github.com/sindresorhus/awesome-nodejs#command-line-utilities)

 ---

 <div align="center">
 	<b>
 		<a href="https://tidelift.com/subscription/pkg/npm-meow?utm_source=npm-meow&utm_medium=referral&utm_campaign=readme">Get professional support for this package with a Tidelift subscription</a>
 	</b>
 	<br>
 	<sub>
 		Tidelift helps make open source sustainable for maintainers while giving companies<br>assurances about security, maintenance, and licensing for their dependencies.
 	</sub>
 </div>
	# meow

	> CLI app helper

	![](meow.gif)

	## Features

	- Parses arguments
	- Converts flags to [camelCase](https://github.com/sindresorhus/camelcase)
	- Negates flags when using the `--no-` prefix
	- Outputs version when `--version`
	- Outputs description and supplied help text when `--help`
	- Makes unhandled rejected promises [fail hard](https://github.com/sindresorhus/hard-rejection) instead of the default silent fail
	- Sets the process title to the binary name defined in package.json

	## Install

	```
	$ npm install meow
	```

	## Usage

	```
	$ ./foo-app.js unicorns --rainbow
	```

	CommonJS

	```js
	#!/usr/bin/env node
	'use strict';
	const meow = require('meow');
	const foo = require('.');

	const cli = meow(`
	Usage
	$ foo <input>

	Options
	--rainbow, -r Include a rainbow

	Examples
	$ foo unicorns --rainbow
	🌈 unicorns 🌈
	`, {
	flags: {
	rainbow: {
	type: 'boolean',
	alias: 'r'
	}
	}
	});
	/*
	{
	input: ['unicorns'],
	flags: {rainbow: true},
	...
	}
	*/

	foo(cli.input[0], cli.flags);
	```

	ES Modules

	```js
	#!/usr/bin/env node
	import {createRequire} from 'module';
	import foo from './lib/index.js';

	const meow = createRequire(import.meta.url)('meow');

	const cli = meow(`
	Usage
	$ foo <input>

	Options
	--rainbow, -r Include a rainbow

	Examples
	$ foo unicorns --rainbow
	🌈 unicorns 🌈
	`, {
	flags: {
	rainbow: {
	type: 'boolean',
	alias: 'r'
	}
	}
	});
	/*
	{
	input: ['unicorns'],
	flags: {rainbow: true},
	...
	}
	*/

	foo(cli.input[0], cli.flags);
	```

	## API

	### meow(helpText, options?)
	### meow(options)

	Returns an `object` with:

	- `input` (Array) - Non-flag arguments
	- `flags` (Object) - Flags converted to camelCase excluding aliases
	- `unnormalizedFlags` (Object) - Flags converted to camelCase including aliases
	- `pkg` (Object) - The `package.json` object
	- `help` (string) - The help text used with `--help`
	- `showHelp([exitCode=2])` (Function) - Show the help text and exit with `exitCode`
	- `showVersion()` (Function) - Show the version text and exit

	#### helpText

	Type: `string`

	Shortcut for the `help` option.

	#### options

	Type: `object`

	##### flags

	Type: `object`

	Define argument flags.

	The key is the flag name in camel-case and the value is an object with any of:

	- `type`: Type of value. (Possible values: `string` `boolean` `number`)
	- `alias`: Usually used to define a short flag alias.
	- `default`: Default value when the flag is not specified.
	- `isRequired`: Determine if the flag is required. (Default: false)
	- If it's only known at runtime whether the flag is required or not, you can pass a `Function` instead of a `boolean`, which based on the given flags and other non-flag arguments, should decide if the flag is required. Two arguments are passed to the function:
	- The first argument is the flags object, which contains the flags converted to camel-case excluding aliases.
	- The second argument is the input string array, which contains the non-flag arguments.
	- The function should return a `boolean`, true if the flag is required, otherwise false.
	- `isMultiple`: Indicates a flag can be set multiple times. Values are turned into an array. (Default: false)
	- Multiple values are provided by specifying the flag multiple times, for example, `$ foo -u rainbow -u cat`. Space- or comma-separated values are [currently not supported](https://github.com/sindresorhus/meow/issues/164).

	Note that flags are always defined using a camel-case key (`myKey`), but will match arguments in kebab-case (`--my-key`).

	Example:

	```js
	flags: {
	unicorn: {
	type: 'string',
	alias: 'u',
	default: ['rainbow', 'cat'],
	isMultiple: true,
	isRequired: (flags, input) => {
	if (flags.otherFlag) {
	return true;
	}

	return false;
	}
	}
	}
	```

	##### description

	Type: `string \| boolean`\
	Default: The package.json `"description"` property

	Description to show above the help text.

	Set it to `false` to disable it altogether.

	##### help

	Type: `string \| boolean`

	The help text you want shown.

	The input is reindented and starting/ending newlines are trimmed which means you can use a [template literal](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/template_strings) without having to care about using the correct amount of indent.

	The description will be shown above your help text automatically.

	##### version

	Type: `string \| boolean`\
	Default: The package.json `"version"` property

	Set a custom version output.

	##### autoHelp

	Type: `boolean`\
	Default: `true`

	Automatically show the help text when the `--help` flag is present. Useful to set this value to `false` when a CLI manages child CLIs with their own help text.

	This option is only considered when there is only one argument in `process.argv`.

	##### autoVersion

	Type: `boolean`\
	Default: `true`

	Automatically show the version text when the `--version` flag is present. Useful to set this value to `false` when a CLI manages child CLIs with their own version text.

	This option is only considered when there is only one argument in `process.argv`.

	##### pkg

	Type: `object`\
	Default: Closest package.json upwards

	package.json as an `object`.

	You most likely don't need this option.

	##### argv

	Type: `string[]`\
	Default: `process.argv.slice(2)`

	Custom arguments object.

	##### inferType

	Type: `boolean`\
	Default: `false`

	Infer the argument type.

	By default, the argument `5` in `$ foo 5` becomes a string. Enabling this would infer it as a number.

	##### booleanDefault

	Type: `boolean \| null \| undefined`\
	Default: `false`

	Value of `boolean` flags not defined in `argv`.

	If set to `undefined`, the flags not defined in `argv` will be excluded from the result.
	The `default` value set in `boolean` flags take precedence over `booleanDefault`.

	_Note: If used in conjunction with `isMultiple`, the default flag value is set to `[]`._

	__Caution: Explicitly specifying `undefined` for `booleanDefault` has different meaning from omitting key itself.__

	Example:

	```js
	const meow = require('meow');

	const cli = meow(`
	Usage
	$ foo

	Options
	--rainbow, -r Include a rainbow
	--unicorn, -u Include a unicorn
	--no-sparkles Exclude sparkles

	Examples
	$ foo
	🌈 unicorns✨🌈
	`, {
	booleanDefault: undefined,
	flags: {
	rainbow: {
	type: 'boolean',
	default: true,
	alias: 'r'
	},
	unicorn: {
	type: 'boolean',
	default: false,
	alias: 'u'
	},
	cake: {
	type: 'boolean',
	alias: 'c'
	},
	sparkles: {
	type: 'boolean',
	default: true
	}
	}
	});
	/*
	{
	flags: {
	rainbow: true,
	unicorn: false,
	sparkles: true
	},
	unnormalizedFlags: {
	rainbow: true,
	r: true,
	unicorn: false,
	u: false,
	sparkles: true
	},
	…
	}
	*/
	```

	##### hardRejection

	Type: `boolean`\
	Default: `true`

	Whether to use [`hard-rejection`](https://github.com/sindresorhus/hard-rejection) or not. Disabling this can be useful if you need to handle `process.on('unhandledRejection')` yourself.

	#### allowUnknownFlags

	Type `boolean`\
	Default: `true`

	Whether to allow unknown flags or not.

	## Promises

	Meow will make unhandled rejected promises [fail hard](https://github.com/sindresorhus/hard-rejection) instead of the default silent fail. Meaning you don't have to manually `.catch()` promises used in your CLI.

	## Tips

	See [`chalk`](https://github.com/chalk/chalk) if you want to colorize the terminal output.

	See [`get-stdin`](https://github.com/sindresorhus/get-stdin) if you want to accept input from stdin.

	See [`conf`](https://github.com/sindresorhus/conf) if you need to persist some data.

	See [`update-notifier`](https://github.com/yeoman/update-notifier) if you want update notifications.

	[More useful CLI utilities…](https://github.com/sindresorhus/awesome-nodejs#command-line-utilities)

	---

	<div align="center">
	<b>
	<a href="https://tidelift.com/subscription/pkg/npm-meow?utm_source=npm-meow&utm_medium=referral&utm_campaign=readme">Get professional support for this package with a Tidelift subscription</a>
	</b>
	<br>
	<sub>
	Tidelift helps make open source sustainable for maintainers while giving companies<br>assurances about security, maintenance, and licensing for their dependencies.
	</sub>
	</div>