Re: Clojure/Script pr-str/read-string roundtrip differences

[Brian Jenkins]

Hi, Thomas.

I also found this frustrating. Here's a work-around I came up with:


;; assuming (defrecord Design [id name]) in namespace tektite.model.design
 
(cljs.reader/register-tag-parser!  "tektite.model.design.Design" 
tektite.model.design/map->Design)
 
(extend-protocol IPrintWithWriter
  tektite.model.design/Design
  (-pr-writer [coll writer opts]
(let [pr-pair (fn [keyval] (pr-sequential-writer writer pr-writer "" " 
" "" opts keyval))]
  (pr-sequential-writer writer pr-pair "#tektite.model.design.Design{" 
", " "}" opts coll


On the server side, I read EDN out of the request body with 
clojure.edn/read (because clojure.core/read is 
unsafe for reading evil strings from the internet).  clojure.edn/read 
doesn't pick up new readers
from data_readers.clj or *data-readers* (fortunately), but can be taught 
new tags like this:


(def model-readers {'tektite.model.design.Design 
#'tektite.model.design/map->Design})
 
(defn read-edn-body [context]
  (clojure.edn/read {:readers model-readers, :eof nil}
(java.io.PushbackReader.
 (java.io.InputStreamReader.
  (get-in context [:request :body])
  "UTF-8"


(I use liberator, so the request arrives in a context hash)

Best,
Brian

On Monday, January 7, 2013 1:13:30 AM UTC+1, Thomas Heller wrote:
>
> Hey,
>
> I'm writing a Clojure Webapp with a CLJS Frontend and expected to be able 
> to cljs.reader/read-string everything I pr-str'd on the CLJ side. That 
> however does not work for defrecords and BigDecimals (1.1M) .
>
> 1. defrecord
>
> In CLJ I can:
>
> (ns dummy)
> (defrecord Foo [bar])
> (pr-str (Foo. 1)) ; => "#dummy.Foo{:bar 1}"
>
> in CLJS however this will print as
>
> "#Foo{:bar 1}"
>
> missing the Namespace. I found an old 
> postabout 
> this but no other information.
>
> Also when I pr-str this record in CLJ and cljs.reader/read-string it in 
> CLJS it fails with "Could not find tag parser for dummy.Foo in ("inst" 
> "uuid" "queue") ", although the defrecord exists and is in the same ns 
> (actually a cljsbuild crossover). I figured out that I can 
> (cljs.reader/register-tag-parser! 'dummy.Foo make-foo) but thats seems 
> faulty. I read about EDN and understand why the reader would think its 
> reading a Tag but I can do read-string in CLJ just fine. Shouldnt both 
> sides be equal here?
>

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Re: Clojure/Script pr-str/read-string roundtrip differences

[Brian Jenkins]

Doh!

I was running 0.0-1586 instead of 0.0-1798

Brian

On Monday, January 7, 2013 1:13:30 AM UTC+1, Thomas Heller wrote:
>
> Hey,
>
> I'm writing a Clojure Webapp with a CLJS Frontend and expected to be able 
> to cljs.reader/read-string everything I pr-str'd on the CLJ side. That 
> however does not work for defrecords and BigDecimals (1.1M) .
>
> 1. defrecord
>
> In CLJ I can:
>
> (ns dummy)
> (defrecord Foo [bar])
> (pr-str (Foo. 1)) ; => "#dummy.Foo{:bar 1}"
>
> in CLJS however this will print as
>
> "#Foo{:bar 1}"
>
> missing the Namespace. I found an old 
> postabout 
> this but no other information.
>
> Also when I pr-str this record in CLJ and cljs.reader/read-string it in 
> CLJS it fails with "Could not find tag parser for dummy.Foo in ("inst" 
> "uuid" "queue") ", although the defrecord exists and is in the same ns 
> (actually a cljsbuild crossover). I figured out that I can 
> (cljs.reader/register-tag-parser! 'dummy.Foo make-foo) but thats seems 
> faulty. I read about EDN and understand why the reader would think its 
> reading a Tag but I can do read-string in CLJ just fine. Shouldnt both 
> sides be equal here?
>
> 2. BigDecimals:
>
> I understand that JavaScript has no BigDecimals and I can live with 
> js/parseFloat on the Client for now, however is there any way I can hint 
> the CLJS printer to print "1.1" as "1.1M"?
>
> On the Topic of EDN: How would I "tag" a value in CLJ(S) to print {:foo 
> "bar"} as #my/tag {:foo "bar"}? The docs only talk about data_readers.clj.
>
> The answers probably lie in the sources, but I hope somebody here has a 
> quick answer. ;)
>
> Cheers,
> /thomas
>
> PS: I'd actually prefer using "tagged" literals instead of the defrecord 
> constructor form since I dont trust anything coming from the client even it 
> looks like clojure data. Is there some protocol I can implement for the 
> record and have it print as tagged instead? For CLJ and CLJS? :)
>
>
>

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