feat: extract fixRequestBody to external handler

src/handlers/fix-request-body.ts

@@ -0,0 +1,26 @@
+import { ClientRequest } from 'http';
+import type { Request } from '../types';
+import * as querystring from 'querystring';
+
+/**
+ * Fix proxied body if bodyParser is involved.
+ */
+export function fixRequestBody(proxyReq: ClientRequest, req: Request) {
+  if (!req.body || !Object.keys(req.body).length) {
+    return;
+  }
+
+  const contentType = proxyReq.getHeader('Content-Type') as string;
+  const writeBody = (bodyData: string) => {
+    proxyReq.setHeader('Content-Length', Buffer.byteLength(bodyData));
+    proxyReq.write(bodyData);
+  };
+
+  if (contentType.includes('application/json')) {
+    writeBody(JSON.stringify(req.body));
+  }
+
+  if (contentType === 'application/x-www-form-urlencoded') {
+    writeBody(querystring.stringify(req.body));
+  }
+}

src/handlers/public.ts

@@ -1 +1,2 @@
 export { responseInterceptor } from './response-interceptor';
+export { fixRequestBody } from './fix-request-body';

src/http-proxy-middleware.ts

@@ -1,10 +1,8 @@
-import { ClientRequest } from 'http';
 import type * as https from 'https';
 import type * as express from 'express';
 import type { Filter, Request, RequestHandler, Response, Options } from './types';
 import * as httpProxy from 'http-proxy';
 import { createConfig, Config } from './config-factory';
-import * as querystring from 'querystring';
 import * as contextMatcher from './context-matcher';
 import * as handlers from './_handlers';
 import { getArrow, getInstance } from './logger';
@@ -35,9 +33,6 @@ export class HttpProxyMiddleware {
     // log errors for debug purpose
     this.proxy.on('error', this.logError);
 
-    // fix proxied body if bodyParser is involved
-    this.proxy.on('proxyReq', this.fixBody);
-
     // https://github.com/chimurai/http-proxy-middleware/issues/19
     // expose function to upgrade externally
     (this.middleware as any).upgrade = (req, socket, head) => {
@@ -198,24 +193,4 @@ export class HttpProxyMiddleware {
 
     this.logger.error(errorMessage, requestHref, targetHref, err.code || err, errReference);
   };
-
-  private fixBody = (proxyReq: ClientRequest, req: Request) => {
-    if (!req.body || !Object.keys(req.body).length) {
-      return;
-    }
-
-    const contentType = proxyReq.getHeader('Content-Type') as string;
-    const writeBody = (bodyData: string) => {
-      proxyReq.setHeader('Content-Length', Buffer.byteLength(bodyData));
-      proxyReq.write(bodyData);
-    };
-
-    if (contentType.includes('application/json')) {
-      writeBody(JSON.stringify(req.body));
-    }
-
-    if (contentType === 'application/x-www-form-urlencoded') {
-      writeBody(querystring.stringify(req.body));
-    }
-  };
 }

test/e2e/_utils.ts

@@ -1,7 +1,7 @@
 import * as express from 'express';
 import { Express, RequestHandler } from 'express';
 
-export { createProxyMiddleware, responseInterceptor } from '../../dist/index';
+export { createProxyMiddleware, responseInterceptor, fixRequestBody } from '../../dist/index';
 
 export function createApp(...middleware: RequestHandler[]): Express {
   const app = express();

test/e2e/http-proxy-middleware.spec.ts

@@ -1,4 +1,4 @@
-import { createProxyMiddleware, createApp, createAppWithPath } from './_utils';
+import { createProxyMiddleware, createApp, createAppWithPath, fixRequestBody } from './_utils';
 import * as request from 'supertest';
 import { Mockttp, getLocal, CompletedRequest } from 'mockttp';
 import { Request, Response } from '../../src/types';
@@ -86,6 +86,7 @@ describe('E2E http-proxy-middleware', () => {
             bodyParser.urlencoded({ extended: false }),
             createProxyMiddleware('/api', {
               target: `http://localhost:${mockTargetServer.port}`,
+              onProxyReq: fixRequestBody,
             })
           )
         );
@@ -102,6 +103,7 @@ describe('E2E http-proxy-middleware', () => {
             bodyParser.json(),
             createProxyMiddleware('/api', {
               target: `http://localhost:${mockTargetServer.port}`,
+              onProxyReq: fixRequestBody,
             })
           )
         );