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argument.js
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Sat, Dec 14, 02:21

argument.js
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const { InvalidArgumentError } = require('./error.js');
// @ts-check
class Argument {
/**
* Initialize a new command argument with the given name and description.
* The default is that the argument is required, and you can explicitly
* indicate this with <> around the name. Put [] around the name for an optional argument.
*
* @param {string} name
* @param {string} [description]
*/
constructor(name, description) {
this.description = description || '';
this.variadic = false;
this.parseArg = undefined;
this.defaultValue = undefined;
this.defaultValueDescription = undefined;
this.argChoices = undefined;
switch (name[0]) {
case '<': // e.g. <required>
this.required = true;
this._name = name.slice(1, -1);
break;
case '[': // e.g. [optional]
this.required = false;
this._name = name.slice(1, -1);
break;
default:
this.required = true;
this._name = name;
break;
}
if (this._name.length > 3 && this._name.slice(-3) === '...') {
this.variadic = true;
this._name = this._name.slice(0, -3);
}
}
/**
* Return argument name.
*
* @return {string}
*/
name() {
return this._name;
};
/**
* @api private
*/
_concatValue(value, previous) {
if (previous === this.defaultValue || !Array.isArray(previous)) {
return [value];
}
return previous.concat(value);
}
/**
* Set the default value, and optionally supply the description to be displayed in the help.
*
* @param {any} value
* @param {string} [description]
* @return {Argument}
*/
default(value, description) {
this.defaultValue = value;
this.defaultValueDescription = description;
return this;
};
/**
* Set the custom handler for processing CLI command arguments into argument values.
*
* @param {Function} [fn]
* @return {Argument}
*/
argParser(fn) {
this.parseArg = fn;
return this;
};
/**
* Only allow option value to be one of choices.
*
* @param {string[]} values
* @return {Argument}
*/
choices(values) {
this.argChoices = values;
this.parseArg = (arg, previous) => {
if (!values.includes(arg)) {
throw new InvalidArgumentError(`Allowed choices are ${values.join(', ')}.`);
}
if (this.variadic) {
return this._concatValue(arg, previous);
}
return arg;
};
return this;
};
/**
* Make option-argument required.
*/
argRequired() {
this.required = true;
return this;
}
/**
* Make option-argument optional.
*/
argOptional() {
this.required = false;
return this;
}
}
/**
* Takes an argument and returns its human readable equivalent for help usage.
*
* @param {Argument} arg
* @return {string}
* @api private
*/
function humanReadableArgName(arg) {
const nameOutput = arg.name() + (arg.variadic === true ? '...' : '');
return arg.required
? '<' + nameOutput + '>'
: '[' + nameOutput + ']';
}
exports.Argument = Argument;
exports.humanReadableArgName = humanReadableArgName;

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