Maps in sets produce an exception when trying to hash due to sorting of the set

[RutledgePaulV]

Since maps don't implement Comparable the sorting of the set during the hashing process fails. I was expecting aesahaettr to handle any composition of plain clojure data. Is it fair to call this a bug? I can take a look and try to provide a PR if so.

To reproduce:

(æsahættr/hash-object (æsahættr/md5) {:bogos #{{:test "this"} {:test "that"}}})

The stacktrace:

#error{:cause "clojure.lang.PersistentArrayMap cannot be cast to java.lang.Comparable",
       :via [{:type java.lang.ClassCastException,
              :message "clojure.lang.PersistentArrayMap cannot be cast to java.lang.Comparable",
              :at [clojure.lang.Util compare "Util.java" 153]}],
       :trace [[clojure.lang.Util compare "Util.java" 153]
               [clojure.core$compare invokeStatic "core.clj" 832]
               [clojure.core$compare invoke "core.clj" 823]
               [clojure.lang.AFunction compare "AFunction.java" 47]
               [java.util.TimSort countRunAndMakeAscending "TimSort.java" 355]
               [java.util.TimSort sort "TimSort.java" 220]
               [java.util.Arrays sort "Arrays.java" 1438]
               [clojure.core$sort invokeStatic "core.clj" 3107]
               [clojure.core$sort invokeStatic "core.clj" 3094]
               [clojure.core$sort invoke "core.clj" 3094]
               [æsahættr$eval10961$fn__10962 invoke "æsahættr.clj" 207]
               [æsahættr$eval10936$fn__10937$G__10927__10944 invoke "æsahættr.clj" 167]
               [æsahættr$eval10991$fn__10992 invoke "æsahættr.clj" 193]
               [æsahættr$eval10936$fn__10937$G__10927__10944 invoke "æsahættr.clj" 167]
               [æsahættr$eval10981$fn__10982 invoke "æsahættr.clj" 211]
               [æsahættr$eval10936$fn__10937$G__10927__10944 invoke "æsahættr.clj" 167]
               [æsahættr$eval10977$fn__10978 invoke "æsahættr.clj" 202]
               [æsahættr$eval10936$fn__10937$G__10927__10944 invoke "æsahættr.clj" 167]
               [æsahættr$reify__10955 funnel "æsahættr.clj" 177]
               [com.google.common.hash.AbstractByteHasher putObject "AbstractByteHasher.java" 119]
               [com.google.common.hash.AbstractStreamingHashFunction hashObject "AbstractStreamingHashFunction.java" 37]
               [æsahættr$hash_object invokeStatic "æsahættr.clj" 156]
               [æsahættr$hash_object invoke "æsahættr.clj" 150]
               [app.util_test$eval52789 invokeStatic "form-init3332181017406736896.clj" 1]
               [app.util_test$eval52789 invoke "form-init3332181017406736896.clj" 1]
               [clojure.lang.Compiler eval "Compiler.java" 7062]
               [clojure.lang.Compiler eval "Compiler.java" 7025]
               [clojure.core$eval invokeStatic "core.clj" 3206]
               [clojure.core$eval invoke "core.clj" 3202]
               [clojure.main$repl$read_eval_print__8572$fn__8575 invoke "main.clj" 243]
               [clojure.main$repl$read_eval_print__8572 invoke "main.clj" 243]
               [clojure.main$repl$fn__8581 invoke "main.clj" 261]
               [clojure.main$repl invokeStatic "main.clj" 261]
               [clojure.main$repl doInvoke "main.clj" 177]
               [clojure.lang.RestFn invoke "RestFn.java" 1523]
               [clojure.tools.nrepl.middleware.interruptible_eval$evaluate$fn__51535 invoke "interruptible_eval.clj" 87]
               [clojure.lang.AFn applyToHelper "AFn.java" 152]
               [clojure.lang.AFn applyTo "AFn.java" 144]
               [clojure.core$apply invokeStatic "core.clj" 657]
               [clojure.core$with_bindings_STAR_ invokeStatic "core.clj" 1965]
               [clojure.core$with_bindings_STAR_ doInvoke "core.clj" 1965]
               [clojure.lang.RestFn invoke "RestFn.java" 425]
               [clojure.tools.nrepl.middleware.interruptible_eval$evaluate invokeStatic "interruptible_eval.clj" 85]
               [clojure.tools.nrepl.middleware.interruptible_eval$evaluate invoke "interruptible_eval.clj" 55]
               [clojure.tools.nrepl.middleware.interruptible_eval$interruptible_eval$fn__51580$fn__51583
                invoke
                "interruptible_eval.clj"
                222]
               [clojure.tools.nrepl.middleware.interruptible_eval$run_next$fn__51575
                invoke
                "interruptible_eval.clj"
                190]
               [clojure.lang.AFn run "AFn.java" 22]
               [java.util.concurrent.ThreadPoolExecutor runWorker "ThreadPoolExecutor.java" 1149]
               [java.util.concurrent.ThreadPoolExecutor$Worker run "ThreadPoolExecutor.java" 624]
               [java.lang.Thread run "Thread.java" 748]]}

[aphyr]

We sort maps to ensure the results don't depend on the hash function used. A commutative hash function would remove the need for sorting--looks like I considered this when I wrote aesahaettr (https://github.com/aphyr/aesahaettr/blob/master/src/%C3%A6sah%C3%A6ttr.clj#L197-L203) but never figured it out. If you have ideas, go for it!