In clojure.spec, how can I declare a map that accepts only certain keys?
*{::a 1 ::b 2 ::BAD 3}* does conform to *(s/keys :req :req [::a ::b])*, but
I want a spec that will be bothered by ::BAD or any other undeclared key.
My use case: I am introducing spec to some legacy code, and I want to be
warned if I have failed to specify some elements that may appear in my map.
Question 2:
So, assuming that this is not possible currently, I brute-forced it with:
*(defn- key-checker [valid-keys]*
* (fn [map-to-check]*
* (empty? (clojure.set/difference (into #{} (keys map-to-check))
valid-keys))))*
*(s/def ::my-map (s/and (s/keys :req [::a ::b]) (key-checker #{::a ::b})))*
Ignoring the ugly, and easily fixable, smell of the duplicated set of keys,
this has a bigger problem:
If the predicate fails, the error that assert gives me is *"{... big ugly
map ...} fails predicate: (key-checker #{::a ::b})"* with no easy way for
the viewer to see which key failed. Can I somehow hook into the explain
mechanism to give a more useful message?
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