Fix non-json outputs

Sometimes youtube-dl won't return JSON. It can return a simple string (when using the "-g" or "--get-url" flags for instance). This commit, with the minimum amount of modifications possible, tries to handle this case.

Comes with a test

lib/youtube-dl.js

@@ -238,6 +238,11 @@ ytdl.exec = function exec(url, args, options, callback) {
  * @returns {Object}
  */
 function parseInfo(data) {
+ // Youtube-dl might return just an url as a string when using the "-g" or "--get-url" flag
+ if (typeof data === "string")
+ if (data.startsWith("http"))
+ data = JSON.stringify({url: data})
+
  const info = JSON.parse(data);
 
  // Add and process some entries to keep backwards compatibility
@@ -316,6 +321,13 @@ ytdl.getInfo = function getInfo(url, args, options, callback) {
  if (err) return callback(err);
  let info;
 
+ // If using the "-g" or "--get-url" flag youtube-dl will return just a string (the URL to the video) which messes up the parsing
+ // This fixes this behaviour
+ if (args.indexOf('-g') > -1 || args.indexOf('--get-url') > -1 )
+ if (Array.isArray(data))
+ if(data.length >= 2)
+ data.splice(0, 1)
+
  try {
  info = data.map(parseInfo);
  } catch (err) {