Should fnhouse look at the :path-info key?

[gfredericks]

We just converted a bunch of routes from compojure to fnhouse, and noticed that they didn't work when deployed to a jboss context (with a route prefix).

As best as I can tell, the request coming in from the jboss machinery has at least three interesting keys:

{...
 :context "/my-prefix"
 :uri "/my-prefix/and/the/path"
 :path-info "/and/the/path"
 ...}

It seems that compojure was able to use the :path-info key when available, but fnhouse does not.

The ring spec does not mention :path-info or :context, so I can't say how standard these are.

Obviously there are some easy workarounds here, but I was wondering if fnhouse ought to support this somehow.

[w01fe]

Thanks for the report.

My inclination is that this is better handled in middleware around the fnhouse root handler than within fnhouse itself. That said, I'm not familiar with jboss; does that seem reasonable, or do you have an argument for why fnhouse should know about this?

[gfredericks]

I think the argument would only make sense if :path-info is the standard way to communicate "your app has been deployed in some kind of container with a path prefix and here is the unprefixed path`.

It does feel pretty middlewarey to me too though, or even like maybe things like jboss should use :uri for the shortened path and put the full thing somewhere else.

I wonder if @tobias has any context (ha!) on this.

[w01fe]

Sounds reasonable to me -- let us know if you figure out the answer :) Thanks!

[jcrossley3]

Hi guys. @tobias referred me. This is not a jboss issue; it's a servlet issue. Neither :context nor :path-info are a part of the ring spec because they're not a part of the http spec. However, they are both part of the servlet spec, and both ring-core and compojure honor them. IMO, any routing library that expects to be deployed in a servlet container (jboss is but one) should honor them. That's not to say they can't be "honored" via middleware, of course.

[gfredericks]

thanks @jcrossley3

Another detail, @w01fe, is that (after glancing at the source code) I believe compojure uses :path-info internally for its own route-prefix mechanism, so that jboss-things and expressions like (context "/foo/:bar" ...) are indistinguishable from the individual handler's perspective.

Fnhouse I think just applies prefixes in a different fashion, using nss->handlers-fn.

In any case I'll leave the final judgement up to you. I'm currently using this middleware, is this what you had in mind or would it be different somehow?

(defn- wrap-fnhouse-path-info-hack
  "Copies the :path-info key of the request to :uri when present, so
  that our routes work when deployed to JBOSS.

  See https://github.com/Prismatic/fnhouse/issues/32 for details."
  [handler]
  (fn [request]
    (-> request
        (cond-> (contains? request :path-info)
          (assoc :uri (:path-info request)
                 ::orig-uri (:uri request)))
        (handler))))

[w01fe]

Thanks for the context, @jcrossley3 -- that's very helpful.

@gfredericks yep, that looks like what I had in mind.

I guess I don't see any harm in concatenating the path-info here, since it seems like probably the least surprising option:

https://github.com/Prismatic/fnhouse/blob/master/src/fnhouse/routes.clj#L129

Or as an alternative, we could add your middleware to the middleware.clj file so it's ready-at-hand.