querystring: Parse multiple separator characters

Fix querystring.parse to handle multiple separator characters

PR-URL: #3807
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/querystring.js

@@ -202,6 +202,7 @@ QueryString.stringify = QueryString.encode = function(obj, sep, eq, options) {
 QueryString.parse = QueryString.decode = function(qs, sep, eq, options) {
   sep = sep || '&';
   eq = eq || '=';
+  const eqLen = eq.length;
   var obj = {};
 
   if (typeof qs !== 'string' || qs.length === 0) {
@@ -235,7 +236,7 @@ QueryString.parse = QueryString.decode = function(qs, sep, eq, options) {
 
     if (idx >= 0) {
       k = decodeStr(x.substring(0, idx), decode);
-      v = decodeStr(x.substring(idx + 1), decode);
+      v = decodeStr(x.substring(idx + eqLen), decode);
     } else {
       k = decodeStr(x, decode);
       v = '';

test/parallel/test-querystring-multichar-separator.js

@@ -0,0 +1,24 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const qs = require('querystring');
+
+assert.deepEqual(
+  qs.parse('foo=>bar&&bar=>baz', '&&', '=>'),
+  {foo: 'bar', bar: 'baz'}
+);
+
+assert.strictEqual(
+  qs.stringify({foo: 'bar', bar: 'baz'}, '&&', '=>'),
+  'foo=>bar&&bar=>baz'
+);
+
+assert.deepEqual(
+  qs.parse('foo==>bar, bar==>baz', ', ', '==>'),
+  {foo: 'bar', bar: 'baz'}
+);
+
+assert.strictEqual(
+  qs.stringify({foo: 'bar', bar: 'baz'}, ', ', '==>'),
+  'foo==>bar, bar==>baz'
+);