TypeScript module augmentation overwrites the original module? -

in node.js / express app, i've had headers.ts file quite while content:

type httpheader = 'x-my-header' | 'x-my-other-header' | 'x-another';  declare module 'express-serve-static-core' {     import * http 'http';     interface request extends http.incomingmessage, express.request {         header(name: httpheader): string | undefined;     } } 

it used compile fine, however, after recent rm -rf node_modules , npm install again, i'm getting lot of errors

error ts2339: property 'get' not exist on type 'request'. error ts2339: property 'end' not exist on type 'response'. 

it seems core issue node_modules/@types/express/index.d.ts resolves import * core "express-serve-static-core" small augmentation , skips loading of real thing entirely. don't know why because have folder node_modules/@types/express-serve-static-core installed.

what be?

judging the:

import * http 'http'; 

inside of module declaration, not, in fact writing module "agumentation" want, rather replacing existing module.

in order write module augmentation need write this:

import { request} 'express-serve-static-core'; import * http 'http';  export type httpheader = 'x-my-header' | 'x-my-other-header' | 'x-another';  declare module 'express-serve-static-core'{     export interface request extends http.incomingmessage, express.request {         header(name: httpheader): string | undefined;     } } 

the first thing note, should me external "file" module (it should have imports , exports).

the second thing note import * http should go outside module augmentation @ not legal inside.

the declared module serves strictly augmentation. not over-write or replace existing express-server-static-core module. in fact, module required exist augmented (if misspell module name not compile' example).

i cannot tell example why code worked before. perhaps there differences in how express-server-static-core declaration files implemented before. if follow example, things should work you.