This issue is somewhat to be expected if you're going to use `js->clj`.
This issue has nothing to do with ClojureScript compiler versions - you
just got lucky before. Google Closure will collapse properties, but some of
these collapsed properties are going to be used to determine protocol
membership. That's it.
I suggest just avoiding `js->clj` and using your own simple helper for
recursively converting JSON into Clojure values. Changing the (admittedly
questionable) behavior of `js->clj` will only lead to more breakage.
HTH,
David
On Sat, Oct 15, 2016 at 11:43 AM, John Szakmeister <j...@szakmeister.net>
wrote:
> I've been using ClojureScript rather successfully for a year now, but
> ran into an interesting issue recently.
>
> I've discovered that js->clj isn't quite working as expected. After
> quite a bit of tearing things down and apart, I discovered it was one
> of the keys in some JSON data coming back from the server that looks
> like:
>
> "Bi": 8
>
> And the resultant error would be:
>
> No protocol method IEncodeClojure.-js->clj defined for type
> object: [object Object]
>
> I don't know why this particular sequence caused a problem, but I
> ended trying to vary things a bit just to see what happens. If I use:
>
> "Bi": 0
>
> I don't see the issue. Any non-zero value though does seem to bring
> the problem about for this sequence of letters though. Similarly, I
> tried varying the two letter sequence, and discovered two others with
> similar problems: Ai, and ba. The latter brought about a different
> error:
>
> [object Object] is not ISeqable
>
> And the pattern with the value needing to be non-zero follows. If the
> value associated with the key is 0, then I don't see a problem.
>
> As I wasn't seeing this issue before, I backpedaled my version of the
> ClojureScript compiler and eventually found that 1.9.56 didn't seem to
> sufffer from the problem. After checking out ClojureScript, and
> bisecting more I found that commit
> bcf60ce194e5292fbc5c4b2d89dfc5a7b886b94c is when the behavior changed
> from behaving correctly to behaving badly, but I think it's a false
> positive.
>
> I then created a much smaller test case, with no other libraries
> involved. This time it's a different set of values that are broken:
>
> * "Ta" with a non-zero value gives: [object Object] is not ISeqable
>
> * "Ub" with a non-zero value gives: No protocol method
> IEmptyableCollection.-empty defined for type object: [object Object]
>
> * "Wb" with a non-zero value gives: No protocol method
> IEncodeClojure.-js->clj defined for type object: [object Object]
>
> If I back up to before the previously mentioned commit, I can still
> cause the problem, though the letter sequences change a bit.
>
> Also, this only appears to happen with advanced optimizations. With
> no optimizations or with whitespace optimizations, there's no issues.
> So it smells like a strange interaction between the ClojureScript
> runtime and the compiler.
>
> Has anyone seen an issue like this before? Does anyone have any ideas
> what is going on? We have these short keys in our data, and it'd be
> pretty painful to make them something else (especially since the names
> are meaningful to those in the know, despite them being cryptic--they
> refer to bit settings on various motors).
>
> I'd be happy to file a ticket, if that's what needs to get done too.
>
> Thanks!
>
> -John
>
> PS Here's the code I used to hunt down problematic keys:
>
> (def alphabet [\a \b \c \d \e \f \g \h \i \j \k \l \m \n \o \p \q \r \s \t
> \u
> \v \w \x \y \z \A \B \C \D \E \F \G \H \I \J \K \L \M \N \O
> \P
> \Q \R \S \T \U \V \W \X \Y \Z])
>
> (enable-console-print!)
>
> (defn ^:export main-page []
> (println"Starting...")
> (doseq [c1 alphabet
> c2 alphabet
> i (range 256)]
> (let [s (str "{\"" c1 c2 "\": " i "}")]
> (try
> ;; (prn :parse-s (js/JSON.parse s))
> ;; (prn :js-clj-parse (js->clj (js/JSON.parse s)))
> (js->clj (js/JSON.parse s))
> (catch js/Error e
> (println "didn't work" s (str e))))
> ))
> (println "Done!"))
>
> Then you can observe the results from the JS console.
>
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