How to get route name of parent route?

[watson]

Goal

For each incoming request I'd like to log the name of the route that matches the request. So given the request GET /users/42 which matches the app.use('/users/:id', ...) route handler I'd like to get the name /users/:id.

Partial solution

I originally used the route property on the request object to extract the route name:

// given a request to `/users/42`, the routeName below would be `/users/:id`
var routeName = req.route.path || req.route.regexp && req.route.regexp.source

Problem

But the above solution doesn't work for nested routes, e.g:

// create sub-app
var admin = express.Router()
admin.get('/users/:id', require('./admin/user'))

// create main app
var app = express()
app.get('/users/:id', require('./user'))
app.use('/a(dmin)?', admin) // mount sub-app under "/admin" and "/a"

When mounting a route like in the above example, the req.route.path property will not contain the parent route. So if someone requests GET /admin/users/42 then req.route.path would just contain /users/:id and not /a(dmin)?/users/:id.

Is there any way inside a route handler to figure out that this was routed through a parent route with the name /a(dmin)??

I first thought to use req.baseUrl, but that will give me the "resolved" path, so I'd get either /a or /admin depending on which actual URL the user typed - I'd like to get the generic route name instead: /a(dmin)?

If this is not possible at all in v4, it would be cool if this could be supported in v5 😃

[wesleytodd]

I was actually looking at this exact feature recently, so we could stat the routes getting hit. We ended up just passing an identifier to the last middleware where we knew its "final form". We did this because the router/route do now know about mounting.

It would be a relatively simple task to make the req.route property into an array. And then instead of re-assigning the route, push onto the array. That would be a breaking change and probably need to go on the v5 router. If you open this issue over there I would love to discuss the other similar features that would be great for this (ie. named routes). And I could probably even whip up the PR if you weren't already interested in doing it.

[tunniclm]

Related to #2501

[wesleytodd]

Haha, @tunniclm that PR is exactly what I just said. Thanks!

EDIT: #2864 <- This pull request linked in the bottom of the #2501

[watson]

@wesleytodd @tunniclm Thanks for your feedback - nice to see that I'm not the only one who've been struggling with this. I guess I'll have to monkey patch my way out of this for the time being and wait for proper support to land in Express v5 😃

[wesleytodd]

@watson NP! Also might want to take a look at using req.app.path(). You might be able to do something like:

var route = req.app.path() + (req.route.path || req.route.regexp && req.route.regexp.source);

Haven't tested that, but it might solve your issue.

[watson]

@wesleytodd It just returns an empty string in my case. It seems to depend on the req.app.parent property being set which apparent isn't set for me

[wesleytodd]

It does return an empty string when NOT in a mounted app. But when you mount like in your OP you should get the mount path. Is that not working?

[watson]

@wesleytodd Seems not to work in my app.

I've made a simple express app showing it. The app in the linked gist will log the following if GET /foo is requested:

GET /foo
--> req.path /
--> req.baseUrl /foo
--> req.app.parent undefined
--> req.app.mountpath /
--> req.app.path() 
sub

Update: The string I'm looking to extract is /foo(bar)? which is the route under which the sub-app is mounted

[wesleytodd]

Looks like it doesnt work with just a router instance, and only with a full express app instance. I pulled down your gist and changed express.Router() to express() and got this output:

node index.js
GET /
--> req.path /
--> req.baseUrl
--> req.app.parent undefined
--> req.app.mountpath /
--> req.app.path()
root
GET /favicon.ico
GET /foo
--> req.path /
--> req.baseUrl /foo
--> req.app.parent function (req, res, next) {
    app.handle(req, res, next);
  }
--> req.app.mountpath /foo(bar)?
--> req.app.path() /foo(bar)?
sub

[watson]

@wesleytodd Interesting. Thanks for clearing that up. Unfortunately I need it to work for instances of express.Router() as well 😞

[wesleytodd]

Yeah, this clearly seems like something worth changing in express and the router. I think opening up an issue on the router is still a good idea.

[watson]

@wesleytodd Ah I see. The reason why the parent and mountpath isn't set when using express.Router() is because it's not seen as a proper Express app.

I've just been looking through the code and as far as I can see the path given as the 1st argument to the use function isn't stored anywhere on any property - so it's not accessible in it's raw form later. It ends up in the Layer constructor where it's just passed into the path-to-regexp module and then forgotten. The Layer constructor is called from the use function on the router - but here it's just discarded as well as far as I can see.

[watson]

@wesleytodd wouldn't it maybe be ok to check if the sub-app was an instance of the express.Router and set its parent and mountpath just as if it was a proper express app? Or would that be a breaking change if someone depends on those being empty in that case?

[wesleytodd]

That behavior seems accurate to what I know. This might be a question for @dougwilson or @jasnell for the breaking change question.