feat: parseFromUrl does not resolve relative references (asyncapi#504)

lib/parser.js

@@ -133,10 +133,20 @@ function parseFromUrl(url, fetchOptions, options) {
   //To not break the API by changing argument position and to silet the linter it is just better to move adding
   if (!fetchOptions) fetchOptions = {};
 
+  // When executed in multiple async calls, 'checkErrorWrapper' passes URL
+  // string as an object by reference. In this case 'String.replace()' method
+  // mutates original URL string causing test with multiple async calls to fail.
+  // Thus completely independent object containing URL string is created for
+  // future manipulation.
+  const urlCopy = new String(url);
+
+  const indexLastSlashPosition = urlCopy.lastIndexOf('/');
+  const baseUrl = urlCopy.substring(0, indexLastSlashPosition + 1);
+
   return new Promise((resolve, reject) => {
     fetch(url, fetchOptions)
       .then(res => res.text())
-      .then(doc => parse(doc, options))
+      .then(doc => parse(doc, { path: baseUrl }))
       .then(result => resolve(result))
       .catch(e => {
         if (e instanceof ParserError) return reject(e);