fix(error handler): fix confusing error message (#509)

Author: chimurai

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## next
 
+- fix(errorHandler): fix confusing error message ([#509](https://github.com/chimurai/http-proxy-middleware/pull/509))
 - fix(proxy): close proxy when server closes ([#508](https://github.com/chimurai/http-proxy-middleware/pull/508))
 - refactor(lodash): remove lodash ([#459](https://github.com/chimurai/http-proxy-middleware/pull/459)) ([#507](https://github.com/chimurai/http-proxy-middleware/pull/507)) ([TrySound](https://github.com/TrySound))
 - fix(ETIMEDOUT): return 504 on ETIMEDOUT ([#480](https://github.com/chimurai/http-proxy-middleware/pull/480)) ([aremishevsky](https://github.com/aremishevsky))

src/handlers.ts

@@ -1,3 +1,4 @@
+import type * as express from 'express';
 import camelcase = require('camelcase');
 import { getInstance } from './logger';
 const logger = getInstance();
@@ -42,7 +43,7 @@ export function getHandlers(options) {
   return handlers;
 }
 
-function defaultErrorHandler(err, req, res) {
+function defaultErrorHandler(err, req: express.Request, res: express.Response) {
   const host = req.headers && req.headers.host;
   const code = err.code;
 
@@ -63,7 +64,7 @@ function defaultErrorHandler(err, req, res) {
     }
   }
 
-  res.end('Error occured while trying to proxy to: ' + host + req.url);
+  res.end(`Error occured while trying to proxy: ${host}${req.url}`);
 }
 
 function logClose(req, socket, head) {

test/unit/handlers.spec.ts

@@ -119,7 +119,7 @@ describe('default proxy error handler', () => {
 
   it('should end the response and return error message', () => {
     proxyError(mockError, mockReq, mockRes, proxyOptions);
-    expect(errorMessage).toBe('Error occured while trying to proxy to: localhost:3000/api');
+    expect(errorMessage).toBe('Error occured while trying to proxy: localhost:3000/api');
   });
 
   it('should not set the http status code to: 500 if headers have already been sent', () => {
@@ -131,6 +131,6 @@ describe('default proxy error handler', () => {
   it('should end the response and return error message', () => {
     mockRes.headersSent = true;
     proxyError(mockError, mockReq, mockRes, proxyOptions);
-    expect(errorMessage).toBe('Error occured while trying to proxy to: localhost:3000/api');
+    expect(errorMessage).toBe('Error occured while trying to proxy: localhost:3000/api');
   });
 });