express: project-local middleware extending Express.Request - express

Question

I am working on a node server based on express and written in TypeScript 1.7. I'm using some project-specific middlewares, that extend the existing express Request or Response interface, but I can't get it completely working yet (without tsc complaining about not finding X in req or res). I've found other questions about this issue, but they are either out of date (I guess) or the solution is not straight forward.
I took a look at the definition of an existing middleware, but I didn't get it working without manually writing separate d.ts files and referencing them in typings/tsd.d.ts. This is my setup:
// middleware/foobar.ts
declare module Express {
export interface Request {
foobar?: string;
}
}
/* my project-related middleware extends the request by `foobar` */
export = function(req: Express.Request, res, next) {
req.foobar = 'FooBar';
next();
};
// main.ts
import express = require('express');
var app = express();
app.use(require('./middleware/foobar'));
app.get('/foobar', (req, res) => {
/* tsc: Property 'foobar' does not exist on type 'Request' */
res.send(req.foobar);
});
What's the best practice for extending express' Request and Response interfaces? If possible, without the need of writing a separated d.ts, manipulating anything within the typings directory or using /// <reference path="..." /> comments.

Answer 1

I've found a solution myself, using this example as a reference. My middleware needs to be wrapped in a declared module, so middleware/foobar.ts looks like this:
declare module Express {
export interface Request {
foobar?: string;
}
}
declare module 'foobar' {
function foobar(req: Express.Request, res, next) {
req.foobar = 'FooBar';
next();
}
export = foobar;
}
It's even a bit more trickier if you are using classes or other imported stuff within your middleware. In my example, my middleware uses my own "EntityManager" class, which is an abstraction to the database connection (mysql for me). My middleware (it's middleware/database.ts for me) looks like this now:
declare module Express {
import { Manager as EntityManager } from 'entity-manager';
export interface Request {
entityManager?: EntityManager;
}
}
declare module 'database' {
import * as mysql from 'mysql';
import { Manager as EntityManager } from 'entity-manager';
/* some middleware-related code */
var pool = mysql.createPool(...);
var entityManager = new EntityManager(pool);
/* *** */
/* the actual exported function */
function database(req: Express.Request, res, next) {
req.entityManager = entityManager;
next();
};
export = database;
}
Note that my EntityManager class is imported twice, once per module declaration. It did not seem to work by just importing it above both modules.
UPDATE
Having the actual code in a declared module ('database' in my case) produces no output in the JS file.
Having that code within a regular module requires the name not being in apostrophes (i.e. hyphens would not be allowed there for example) and doesn't produce a one-function-export code either.
Having the actual code completely out of a module (so there's only the declared Express module with the extended Request) produces correct JS but my text editor can't find entityManager in req anymore.
It seems like I'm needed to put the typings (my own extensions to Express.Request for example) into a dedicated d.ts file, where no actual code is present.