Deferred are deref'ed by compojure/routes. How to get around this?

[Martin Raison]

Aleph's README says handlers may return a deferred to represent an eventual
response.
In the HTTP examples
<http://ideolalia.com/aleph/literate.html#aleph.examples.http>, it also
uses compojure/routes to define the routes.

However, before returning the response to the middleware, compojure
actually "renders" the result. This means that, since deferred implements
IDeref, compojure calls deref
<https://github.com/weavejester/compojure/blob/639fffd3f8b77153644d0c9b87bca5af56be0cb0/src/compojure/response.clj#L36>
on the deferred before passing the response back to the middleware. Isn't
this bad? Does anyone have a good solution to prevent compojure from
deref'ing the result? (both my handler and my middleware do asynchronous
operations, so it seems suboptimal to have a deref in the middle of the
chain)

[Robert Zabel]

Hi,
i think you could do something like this:

(extend-type Deferred
Renderable
(render [this req]
(d/chain this #(render % req))))

Post by Martin Raison
Aleph's README says handlers may return a deferred to represent an
eventual response.
In the HTTP examples
<http://ideolalia.com/aleph/literate.html#aleph.examples.http>, it also
uses compojure/routes to define the routes.
However, before returning the response to the middleware, compojure
actually "renders" the result. This means that, since deferred implements
IDeref, compojure calls deref
<https://github.com/weavejester/compojure/blob/639fffd3f8b77153644d0c9b87bca5af56be0cb0/src/compojure/response.clj#L36>
on the deferred before passing the response back to the middleware. Isn't
this bad? Does anyone have a good solution to prevent compojure from
deref'ing the result? (both my handler and my middleware do asynchronous
operations, so it seems suboptimal to have a deref in the middle of the
chain)

[Zach Tellman]

What version of Compojure are you using? I had thought that in the latest,
the values passed through untouched.

Post by Robert Zabel
Hi,
(extend-type Deferred
Renderable
(render [this req]
(d/chain this #(render % req))))

Post by Martin Raison
Aleph's README says handlers may return a deferred to represent an
eventual response.
In the HTTP examples
<http://ideolalia.com/aleph/literate.html#aleph.examples.http>, it also
uses compojure/routes to define the routes.
However, before returning the response to the middleware, compojure
actually "renders" the result. This means that, since deferred implements
IDeref, compojure calls deref
<https://github.com/weavejester/compojure/blob/639fffd3f8b77153644d0c9b87bca5af56be0cb0/src/compojure/response.clj#L36>
on the deferred before passing the response back to the middleware. Isn't
this bad? Does anyone have a good solution to prevent compojure from
deref'ing the result? (both my handler and my middleware do asynchronous
operations, so it seems suboptimal to have a deref in the middle of the
chain)

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[Robert Zabel]

I checked out the latest version on git, they really deref.

Post by Zach Tellman
What version of Compojure are you using? I had thought that in the
latest, the values passed through untouched.

Post by Robert Zabel
Hi,
(extend-type Deferred
Renderable
(render [this req]
(d/chain this #(render % req))))

Post by Martin Raison
Aleph's README says handlers may return a deferred to represent an
eventual response.
In the HTTP examples
<http://ideolalia.com/aleph/literate.html#aleph.examples.http>, it also
uses compojure/routes to define the routes.
However, before returning the response to the middleware, compojure
actually "renders" the result. This means that, since deferred implements
IDeref, compojure calls deref
<https://github.com/weavejester/compojure/blob/639fffd3f8b77153644d0c9b87bca5af56be0cb0/src/compojure/response.clj#L36>
on the deferred before passing the response back to the middleware. Isn't
this bad? Does anyone have a good solution to prevent compojure from
deref'ing the result? (both my handler and my middleware do asynchronous
operations, so it seems suboptimal to have a deref in the middle of the
chain)

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