Fix redirects in case of relative URL

src/node/main.ts

@@ -2,7 +2,7 @@
  *  Copyright (c) Microsoft Corporation. All rights reserved.
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
-import { Url, parse as parseUrl } from 'url';
+import { Url, parse as parseUrl, URL, format } from 'url';
 import * as  https from 'https';
 import * as  http from 'http';
 import * as zlib from 'zlib';
@@ -57,6 +57,15 @@ export const xhr: XHRRequest = (options: XHROptions): Promise<XHRResponse> => {
 			isCompleted = true;
 			if (options.followRedirects > 0 && (res.statusCode >= 300 && res.statusCode <= 303 || res.statusCode === 307)) {
 				let location = res.headers['location'];
+				if(location.startsWith('/')){
+					let endpoint = parseUrl(options.url);
+					location = format({
+						protocol: endpoint.protocol,
+						hostname: endpoint.hostname,
+						port: endpoint.port,
+						pathname: location
+					});
+				}
 				if (location) {
 					let newOptions = {
 						type: options.type, url: location, user: options.user, password: options.password, headers: options.headers,
@@ -141,8 +150,17 @@ function request(options: XHROptions): Promise<RequestResult> {
 
 		let handler = (res: http.IncomingMessage) => {
 			if (res.statusCode >= 300 && res.statusCode < 400 && options.followRedirects && options.followRedirects > 0 && res.headers['location']) {
+				let location = res.headers['location'];
+				if(location.startsWith('/')){
+					location = format({
+						protocol: endpoint.protocol,
+						hostname: endpoint.hostname,
+						port: endpoint.port,
+						pathname: location
+					});
+				}
 				c(<any>request(assign({}, options, {
-					url: res.headers['location'],
+					url: location,
 					followRedirects: options.followRedirects - 1
 				})));
 			} else {
@@ -234,4 +252,4 @@ function getProxyAgent(rawRequestURL: string, options: ProxyOptions = {}): any {
 	};
 
 	return requestURL.protocol === 'http:' ? createHttpProxyAgent(opts) : createHttpsProxyAgent(opts);
-}
+}

src/test/test.ts

@@ -7,6 +7,7 @@ import { createServer, createSecureServer, createProxy, createSecureProxy } from
 import { AddressInfo } from 'net';
 import { promises as fs } from 'fs';
 import { join } from 'path';
+import { IncomingMessage, ServerResponse } from 'http';
 
 test('text content', async t => {
     const testContent = JSON.stringify({ hello: 1, world: true})
@@ -82,4 +83,28 @@ test('proxy https to https', async t => {
 
     server.close();
     proxy.close();
-})
+});
+
+test('relative redirect', async t => {
+    const server = await createServer();
+
+    server.on('request', (req:IncomingMessage, res: ServerResponse) => {
+        if(req.url.includes('/foo')) {
+            res.setHeader('Location', '/bar');
+            res.statusCode = 301;
+            res.end();
+        }
+        if(req.url.includes('/bar')){
+            res.end('Bar');
+        }
+    });
+
+    const serverAddress = server.address() as AddressInfo;
+
+    const response = await xhr({ url: `http://${serverAddress.address}:${serverAddress.port}/foo` });
+
+    t.deepEqual(response.body.toString(), 'Bar');
+    t.is(response.status, 200);
+
+    server.close();
+});