1  'use strict';
 2  const alias = ['stdin', 'stdout', 'stderr'];
 3  
 4  const hasAlias = opts => alias.some(x => Boolean(opts[x]));
 5  
 6  module.exports = opts => {
 7  	if (!opts) {
 8  		return null;
 9  	}
10  
11  	if (opts.stdio && hasAlias(opts)) {
12  		throw new Error(`It's not possible to provide \`stdio\` in combination with one of ${alias.map(x => `\`${x}\``).join(', ')}`);
13  	}
14  
15  	if (typeof opts.stdio === 'string') {
16  		return opts.stdio;
17  	}
18  
19  	const stdio = opts.stdio || [];
20  
21  	if (!Array.isArray(stdio)) {
22  		throw new TypeError(`Expected \`stdio\` to be of type \`string\` or \`Array\`, got \`${typeof stdio}\``);
23  	}
24  
25  	const result = [];
26  	const len = Math.max(stdio.length, alias.length);
27  
28  	for (let i = 0; i < len; i++) {
29  		let value = null;
30  
31  		if (stdio[i] !== undefined) {
32  			value = stdio[i];
33  		} else if (opts[alias[i]] !== undefined) {
34  			value = opts[alias[i]];
35  		}
36  
37  		result[i] = value;
38  	}
39  
40  	return result;
41  };