request-promise-compressed.js

module.exports = request_promise_compressed;
var request	= require('request-promise')
  , bb		= require('bluebird')
  , zlib	= require('zlib');

function request_promise_compressed(url){ // Supports compressed=true;
	if (!url.compressed) return request(url);

	var resolveWithFullResponse	= url.resolveWithFullResponse;
	var encoding			= url.encoding;

	url.headers			= url.headers || {};
	url.headers["Accept-Encoding"]	= url.headers["Accept-Encoding"] || "gzip,deflate";
	url.resolveWithFullResponse	= true;
	url.encoding			= null;

	return request(url).then(function(res){
		// Body:
		var body = (function(){
			switch(res.headers && res.headers['content-encoding']){
			case 'deflate'	: return bb.promisify(zlib.deflate)(res.body);
			case 'gzip'	: return bb.promisify(zlib.gunzip)(res.body);
			default		: return res.body;
			}
		})().then(function(buffer){return buffer.toString(encoding);});
		if (resolveWithFullResponse){
			return body.then(function(b){res.body = b; return res;});
		} else {
			return body;
		}
	});
}

I found that I had to make a clone of the url object in order for this function to work properly:
url = require('util')._extend({}, url)