Does Express or Node return the app/server object as part of the request object?

Question

I am reviewing an older node project (Typhoon blog engine).

In the route definition module, there are several functions that use the statement req.app.{something} where {something} is a function based off of the app object (i.e. the object created from the deprecated express.createServer() or the non-deprecated express()).

I cant find any documentation for express or node that state this object would normally be attached to the request object. Nor do I see anywhere in the project I am reviewing where req.app is explicitly defined.

So is the presence of req.app deprecated behavior for node or express? or is there some deeper magic afoot that I have missed? How is it being done in this project?

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edit

When searching the source, I found the following. I still don't see where it is defined, but it does appear to be used in the express request module.

grep -i -r --exclude-dir=*examples --exclude-dir=*test 'this\.app' ./express
./express/lib/request.js:  var trustProxy = this.app.get('trust proxy');
./express/lib/request.js:  var trustProxy = this.app.get('trust proxy');
./express/lib/request.js:  var offset = this.app.get('subdomain offset');
./express/lib/request.js:  var trustProxy = this.app.get('trust proxy');
./express/lib/response.js:  var app = this.app;


grep -i -r --exclude-dir=*examples --exclude-dir=*test 'app =' ./express
./express/lib/application.js:var app = exports = module.exports = {};
./express/lib/application.js:  if (fn.handle && fn.set) mount_app = fn;
./express/lib/application.js: *      , app = express();
./express/lib/response.js:  var app = this.app;
./express/lib/response.js:    , app = req.app;
./express/lib/express.js:  var app = function(req, res, next) {
./express/support/app.js:var app = express()

Answer 1

It is defined in express/lib/express.js ~line 33:

function createApplication() {
  var app = connect();
  utils.merge(app, proto);
  app.request = { __proto__: req, app: app };
  app.response = { __proto__: res, app: app };
  app.init();
 return app;

}