DELETE without `:params` sends request body `null`

[jonase]

The following call

(DELETE "http://localhost:3000"
        {:format (json-request-format)})

makes an http DELETE request with the request-body null and Content-Length 4 even if no :params are specified.

This is problematic at least on Google App Engine as the web server won't allow a body in DELETE requests

[JulianBirch]

I'm caught between a rock and a hard place on this one. On the other hand, you've got a genuine problem there, on the other the HTTP spec allows bodies in DELETE. Furthermore, null is the correct JSON encoding for no value at all.

I think the easiest way to work around this is to use :format :raw.

I'll try to think of a way to support this without breaking people who actually need DELETE with a body.

[JulianBirch]

I did come up with a way of handling this, but the more I think about it it isn't actually superior to just saying "don't use json on DELETE in google app engine". (The same holds true of TRACE in all environments.)

[JulianBirch]

I think I've come up with a way of handling this well, so I'm re-opening the issue.

[JulianBirch]

Take a look at https://github.com/JulianBirch/cljs-ajax/blob/interceptors/interceptors.md and see what you think.

[rzvavram]

Hey, can you write this solution somewhere more accessible ? What i'm talking about is -> :format :raw for GAE

[ghost]

This is a long time gone, but I'm curious @JulianBirch if you could point me to a RFC (or something) where this is declared:

Furthermore, null is the correct JSON encoding for no value at all

[p-himik]

Just stumbled upon this as well. :format :raw cannot be used since the keywords are not allowed as the format values in the current version. And there's an interesting comment in the source code: "There's no raw-request-format because it's handled by the DirectSubmission code". But the issue is that DirectSubmission works only if the :body is not nil. The workaround is to specify :body "". That way, it's not nil, DirectSubmission works, and there is still nothing to send since the body is empty.

[JulianBirch]

I guess we could make DirectSubmission treat a nil as empty string. Need to make sure it didn't interfere with normal operation, though.

Incidentally, for future reference, the correct behaviour for nil is specified in the MDN schema.

[metametadata]

The example in https://github.com/JulianBirch/cljs-ajax/blob/master/docs/interceptors.md doesn't work in Clojure where body is an InputStream:

(if (ajax.protocols/-body response) 

(I'm not even sure it works in ClojureScript, as I had to compare body with "" instead of nil. But I use transit+json format, not pure json.)

I check Content-Length to make the interceptor work in both Clojure and ClojureScript:

[ajax.core :as ajax]
[ajax.protocols :as ajax-protocols]
...

(def -treat-empty-response-as-nil
  (ajax/to-interceptor
    {:name     "JSON special case nil"
     :response (fn -empty-means-nil
                 [response]
                 ; The "Content-Length" response header is required.
                 ; It's checked in order to avoid consuming the response body input stream in Clojure
                 ; and works in both Clojure and CLJS.
                 (if (= (ajax-protocols/-get-response-header response "Content-Length") "0")
                   (reduced [(ajax/success? (ajax-protocols/-status response)) nil])
                   response))}))

[metametadata]

My previous comment is incorrect because not all responses have Content-Length. So instead of interceptor I settled on a custom parsing function:

(ns foo
  (:require [ajax.interceptors :as ajax-interceptors]
            [ajax.protocols :as ajax-protocols]
            [cognitect.transit :as transit])
  #?(:clj (:import (org.apache.http.nio.entity ContentInputStream))))

; HACK: an alternative to ajax.transit/transit-read-fn which does not choke on empty responses (e.g. on DELETE).
; https://github.com/JulianBirch/cljs-ajax/issues/65.
(defn -read-transit-json
  [response]
  (let [body (ajax-protocols/-body response)
        opts {:handlers ....}]
    #?(:clj
       (if (zero? (.available ^ContentInputStream body))
         nil
         (transit/read (transit/reader body :json opts)))

       :cljs
       (if (empty? body)
         nil
         (transit/read (transit/reader :json opts) body)))))

; HACK: custom response format instead of ajax/transit-response-format
; which always asks server for transit+msgpack.
; https://github.com/JulianBirch/cljs-ajax/issues/240.
(def -response-format (ajax-interceptors/map->ResponseFormat
                        {:content-type ["application/transit+json"]
                         :description  "Transit"
                         :read         -read-transit-json}))

[JulianBirch]

Hmm. I'm coming round to the view we should support this (via a flag) in the base library. And you've done the hard work of figuring out how to do it. I need to figure out how to integrate it best. Think the protocol probably needs a :body-empty method that can then be used by json and transit to default to null.