refactor: minor type improvements

src/handlers/response-interceptor.ts

@@ -67,9 +67,9 @@ export function responseInterceptor<
  */
 function decompress<TReq extends http.IncomingMessage = http.IncomingMessage>(
   proxyRes: TReq,
-  contentEncoding: string
-): TReq {
-  let _proxyRes = proxyRes;
+  contentEncoding?: string
+): TReq | zlib.Gunzip | zlib.Inflate | zlib.BrotliDecompress {
+  let _proxyRes: TReq | zlib.Gunzip | zlib.Inflate | zlib.BrotliDecompress = proxyRes;
   let decompress;
 
   switch (contentEncoding) {

src/http-proxy-middleware.ts

@@ -1,3 +1,4 @@
+import type * as net from 'net';
 import type * as http from 'http';
 import type * as https from 'https';
 import type { RequestHandler, Options, Filter } from './types';
@@ -38,7 +39,7 @@ export class HttpProxyMiddleware<TReq, TRes> {
   }
 
   // https://github.com/Microsoft/TypeScript/wiki/'this'-in-TypeScript#red-flags-for-this
-  public middleware: RequestHandler = async (req, res, next?) => {
+  public middleware: RequestHandler = (async (req, res, next?) => {
     if (this.shouldProxy(this.proxyOptions.pathFilter, req)) {
       try {
         const activeProxyOptions = await this.prepareProxyRequest(req);
@@ -73,7 +74,7 @@ export class HttpProxyMiddleware<TReq, TRes> {
       // use initial request to access the server object to subscribe to http upgrade event
       this.catchUpgradeRequest(server);
     }
-  };
+  }) as RequestHandler;
 
   private registerPlugins(proxy: httpProxy<TReq, TRes>, options: Options<TReq, TRes>) {
     const plugins = getPlugins<TReq, TRes>(options);
@@ -93,7 +94,7 @@ export class HttpProxyMiddleware<TReq, TRes> {
     }
   };
 
-  private handleUpgrade = async (req: http.IncomingMessage, socket, head) => {
+  private handleUpgrade = async (req: http.IncomingMessage, socket: net.Socket, head: Buffer) => {
     if (this.shouldProxy(this.proxyOptions.pathFilter, req)) {
       const activeProxyOptions = await this.prepareProxyRequest(req);
       this.proxy.ws(req, socket, head, activeProxyOptions);
@@ -104,7 +105,10 @@ export class HttpProxyMiddleware<TReq, TRes> {
   /**
    * Determine whether request should be proxied.
    */
-  private shouldProxy = (pathFilter: Filter<TReq>, req: http.IncomingMessage): boolean => {
+  private shouldProxy = (
+    pathFilter: Filter<TReq> | undefined,
+    req: http.IncomingMessage
+  ): boolean => {
     return matchPathFilter(pathFilter, req.url, req);
   };
 
@@ -138,7 +142,7 @@ export class HttpProxyMiddleware<TReq, TRes> {
   };
 
   // Modify option.target when router present.
-  private applyRouter = async (req: http.IncomingMessage, options) => {
+  private applyRouter = async (req: http.IncomingMessage, options: Options<TReq, TRes>) => {
     let newTarget;
 
     if (options.router) {

src/legacy/options-adapter.ts

@@ -24,7 +24,7 @@ export function legacyOptionsAdapter<TReq, TRes>(
   legacyContext: Filter<TReq> | LegacyOptions<TReq, TRes>,
   legacyOptions: LegacyOptions<TReq, TRes>
 ): Options<TReq, TRes> {
-  let options: LegacyOptions<TReq, TRes>;
+  let options: LegacyOptions<TReq, TRes> = {};
   let logger: Logger;
 
   // https://github.com/chimurai/http-proxy-middleware/pull/716
@@ -58,6 +58,8 @@ export function legacyOptionsAdapter<TReq, TRes>(
   } else if (legacyContext && !legacyOptions) {
     options = { ...(legacyContext as LegacyOptions<TReq, TRes>) };
     logger = getLegacyLogger(options);
+  } else {
+    logger = getLegacyLogger({}) as never;
   }
 
   // map old event names to new event names

src/path-filter.ts

@@ -7,7 +7,7 @@ import type * as http from 'http';
 
 export function matchPathFilter<TReq = http.IncomingMessage>(
   pathFilter: Filter<TReq> = '/',
-  uri: string,
+  uri: string | undefined,
   req: http.IncomingMessage
 ): boolean {
   // single path
@@ -34,8 +34,8 @@ export function matchPathFilter<TReq = http.IncomingMessage>(
 
   // custom matching
   if (typeof pathFilter === 'function') {
-    const pathname = getUrlPathName(uri);
-    return pathFilter(pathname, req as unknown as TReq);
+    const pathname = getUrlPathName(uri) as string;
+    return pathFilter(pathname, req as TReq);
   }
 
   throw new Error(ERRORS.ERR_CONTEXT_MATCHER_GENERIC);
@@ -46,18 +46,18 @@ export function matchPathFilter<TReq = http.IncomingMessage>(
  * @param  {String} uri     'http://example.org/api/b/c/d.html'
  * @return {Boolean}
  */
-function matchSingleStringPath(pathFilter: string, uri: string) {
+function matchSingleStringPath(pathFilter: string, uri?: string) {
   const pathname = getUrlPathName(uri);
-  return pathname.indexOf(pathFilter) === 0;
+  return pathname?.indexOf(pathFilter) === 0;
 }
 
-function matchSingleGlobPath(pattern: string | string[], uri: string) {
-  const pathname = getUrlPathName(uri);
+function matchSingleGlobPath(pattern: string | string[], uri?: string) {
+  const pathname = getUrlPathName(uri) as string;
   const matches = micromatch([pathname], pattern);
   return matches && matches.length > 0;
 }
 
-function matchMultiGlobPath(patternList: string | string[], uri: string) {
+function matchMultiGlobPath(patternList: string | string[], uri?: string) {
   return matchSingleGlobPath(patternList, uri);
 }
 
@@ -66,7 +66,7 @@ function matchMultiGlobPath(patternList: string | string[], uri: string) {
  * @param  {String} uri     'http://example.org/api/b/c/d.html'
  * @return {Boolean}
  */
-function matchMultiPath(pathFilterList: string[], uri: string) {
+function matchMultiPath(pathFilterList: string[], uri?: string) {
   let isMultiPath = false;
 
   for (const context of pathFilterList) {
@@ -85,7 +85,7 @@ function matchMultiPath(pathFilterList: string[], uri: string) {
  * @param  {String} uri from req.url
  * @return {String}     RFC 3986 path
  */
-function getUrlPathName(uri: string) {
+function getUrlPathName(uri?: string) {
   return uri && url.parse(uri).pathname;
 }
 

src/path-rewriter.ts

@@ -4,14 +4,16 @@ import { Debug } from './debug';
 
 const debug = Debug.extend('path-rewriter');
 
+type RewriteRule = { regex: RegExp; value: string };
+
 /**
  * Create rewrite function, to cache parsed rewrite rules.
  *
  * @param {Object} rewriteConfig
  * @return {Function} Function to rewrite paths; This function should accept `path` (request.url) as parameter
  */
 export function createPathRewriter(rewriteConfig) {
-  let rulesCache;
+  let rulesCache: RewriteRule[];
 
   if (!isValidRewriteConfig(rewriteConfig)) {
     return;
@@ -52,8 +54,8 @@ function isValidRewriteConfig(rewriteConfig) {
   }
 }
 
-function parsePathRewriteRules(rewriteConfig) {
-  const rules = [];
+function parsePathRewriteRules(rewriteConfig: Record<string, string>) {
+  const rules: RewriteRule[] = [];
 
   if (isPlainObj(rewriteConfig)) {
     for (const [key, value] of Object.entries(rewriteConfig)) {

src/plugins/default/error-response-plugin.ts

@@ -1,15 +1,14 @@
 import { getStatusCode } from '../../status-code';
 import { Plugin } from '../../types';
-import type * as http from 'http';
 
 export const errorResponsePlugin: Plugin = (proxyServer, options) => {
-  proxyServer.on('error', (err, req, res: http.ServerResponse, target?) => {
+  proxyServer.on('error', (err, req, res, target?) => {
     // Re-throw error. Not recoverable since req & res are empty.
     if (!req && !res) {
       throw err; // "Error: Must provide a proper URL as target"
     }
 
-    if (res.writeHead && !res.headersSent) {
+    if ('writeHead' in res && !res.headersSent) {
       const statusCode = getStatusCode((err as unknown as any).code);
       res.writeHead(statusCode);
     }

src/types.ts

@@ -17,7 +17,7 @@ export interface RequestHandler<
   TNext = NextFunction
 > {
   (req: TReq, res: TRes, next?: TNext): void | Promise<void>;
-  upgrade?: (req: http.IncomingMessage, socket: net.Socket, head: any) => void;
+  upgrade: (req: http.IncomingMessage, socket: net.Socket, head: Buffer) => void;
 }
 
 export type Filter<TReq = http.IncomingMessage> =
@@ -67,7 +67,7 @@ export interface Options<TReq = http.IncomingMessage, TRes = http.ServerResponse
    */
   pathRewrite?:
     | { [regexp: string]: string }
-    | ((path: string, req: TReq) => string)
+    | ((path: string, req: TReq) => string | undefined)
     | ((path: string, req: TReq) => Promise<string>);
   /**
    * Access the internal http-proxy server instance to customize behavior

test/e2e/express-error-middleware.spec.ts

@@ -18,7 +18,7 @@ describe('express error middleware', () => {
     const app = createApp(proxyMiddleware, errorMiddleware);
     const response = await request(app).get('/get').expect(504);
 
-    expect(httpProxyError.message).toBe('Must provide a proper URL as target');
+    expect(httpProxyError?.message).toBe('Must provide a proper URL as target');
     expect(response.text).toBe('Something broke!');
   });
 });

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

@@ -256,7 +256,7 @@ describe('E2E http-proxy-middleware', () => {
       });
 
       it('should send request header "host" to target server', async () => {
-        let completedRequest: CompletedRequest;
+        let completedRequest: CompletedRequest | undefined;
 
         await mockTargetServer.forGet().thenCallback((req) => {
           completedRequest = req;
@@ -265,7 +265,7 @@ describe('E2E http-proxy-middleware', () => {
 
         const response = await agent.get(`/api/some/endpoint/index.html`).expect(200);
         expect(response.text).toBe('OK');
-        expect(completedRequest.headers.host).toBe('foobar.dev');
+        expect(completedRequest?.headers.host).toBe('foobar.dev');
       });
     });
 
@@ -374,15 +374,15 @@ describe('E2E http-proxy-middleware', () => {
       });
 
       it('should add `x-added` as custom header to request"', async () => {
-        let completedRequest: CompletedRequest;
+        let completedRequest: CompletedRequest | undefined;
         await mockTargetServer.forGet().thenCallback((req) => {
           completedRequest = req;
           return { statusCode: 200 };
         });
 
         await agent.get(`/api/foo/bar`).expect(200);
 
-        expect(completedRequest.headers['x-added']).toBe('added-from-hpm');
+        expect(completedRequest?.headers['x-added']).toBe('added-from-hpm');
       });
     });
 

test/e2e/plugins.spec.ts

@@ -16,8 +16,8 @@ describe('E2E Plugins', () => {
   });
 
   it('should register a plugin and access the http-proxy object', async () => {
-    let proxyReqUrl: string;
-    let responseStatusCode: number;
+    let proxyReqUrl: string | undefined;
+    let responseStatusCode: number | undefined;
 
     mockTargetServer.forGet('/users/1').thenReply(200, '{"userName":"John"}');
 

test/unit/response-interceptor.spec.ts

@@ -1,9 +1,10 @@
 import { IncomingMessage, ServerResponse } from 'http';
+import { Socket } from 'net';
 
 import { responseInterceptor } from '../../src/handlers/response-interceptor';
 
 const fakeProxyResponse = () => {
-  const httpIncomingMessage = new IncomingMessage(null);
+  const httpIncomingMessage = new IncomingMessage(new Socket());
   httpIncomingMessage._read = () => ({});
   return httpIncomingMessage;
 };
@@ -24,38 +25,32 @@ const waitInterceptorHandler = (ms = 1): Promise<void> =>
 
 describe('responseInterceptor', () => {
   it('should write body on end proxy event', async () => {
-    const httpIncomingMessage = fakeProxyResponse();
-    const response = fakeResponse();
+    const proxyRes = fakeProxyResponse();
+    const req = fakeProxyResponse();
+    const res = fakeResponse();
 
-    responseInterceptor(async () => JSON.stringify({ someField: '' }))(
-      httpIncomingMessage,
-      null,
-      response
-    );
+    responseInterceptor(async () => JSON.stringify({ someField: '' }))(proxyRes, req, res);
 
-    httpIncomingMessage.emit('end');
+    proxyRes.emit('end');
     await waitInterceptorHandler();
 
     const expectedBody = JSON.stringify({ someField: '' });
-    expect(response.setHeader).toHaveBeenCalledWith('content-length', expectedBody.length);
-    expect(response.write).toHaveBeenCalledWith(Buffer.from(expectedBody));
-    expect(response.end).toHaveBeenCalledWith();
+    expect(res.setHeader).toHaveBeenCalledWith('content-length', expectedBody.length);
+    expect(res.write).toHaveBeenCalledWith(Buffer.from(expectedBody));
+    expect(res.end).toHaveBeenCalledWith();
   });
 
   it('should end with error when receive a proxy error event', async () => {
-    const httpIncomingMessage = fakeProxyResponse();
-    const response = fakeResponse();
+    const proxyRes = fakeProxyResponse();
+    const req = fakeProxyResponse();
+    const res = fakeResponse();
 
-    responseInterceptor(async () => JSON.stringify({ someField: '' }))(
-      httpIncomingMessage,
-      null,
-      response
-    );
+    responseInterceptor(async () => JSON.stringify({ someField: '' }))(proxyRes, req, res);
 
-    httpIncomingMessage.emit('error', new Error('some error message'));
+    proxyRes.emit('error', new Error('some error message'));
 
-    expect(response.setHeader).not.toHaveBeenCalled();
-    expect(response.write).not.toHaveBeenCalled();
-    expect(response.end).toHaveBeenCalledWith('Error fetching proxied request: some error message');
+    expect(res.setHeader).not.toHaveBeenCalled();
+    expect(res.write).not.toHaveBeenCalled();
+    expect(res.end).toHaveBeenCalledWith('Error fetching proxied request: some error message');
   });
 });

tsconfig.json

@@ -7,7 +7,9 @@
     "moduleResolution": "node",
     "target": "es2019",
     "incremental": true,
-    "declaration": true
+    "declaration": true,
+    "strict": true,
+    "noImplicitAny": false
   },
   "include": ["./src"]
 }