Cannot use map() with only-optional keys

[mattbishop]

I expect I could spec an object that has only optional keys. Here is a failing unit test:

  describe("map()", () => {
    it("should allow optional-only keys map()", () => {
      const mapSpec = S.spec.map("optional keys", {
        [S.symbol.optional]: {
          banana: S.spec.string
        }
      });

      S.assert(mapSpec, {});
    });
  });

[mattbishop]

Error: Cannot use Keys spec without keys.

[arichiardi]

I double-checked in clojure and it actually works fine so this is probably a missing piece/bug.

boot.user> (s/def ::optional-map (s/keys :opt-un [::a-key]))
:boot.user/optional-map
boot.user> (s/conform ::optional-map {})
{}
boot.user> (s/conform ::optional-map {::a-key 1})
#:boot.user{:a-key 1}

[arichiardi]

If I interpret the code correctly spec does the check in order, starting from the required keys and then using the optional ones...

However in our case, there is a call to keys here, only for required keys. In this case it throws because there are none in there.

So I was thinking of avoid calling that if we don't have required keys. Hopefully @prayerslayer can confirm this is a good approach, all the tests pass smoothly, but I don't know what was the though behind that part.

[arichiardi]

Also I was wondering why there is a return specifically tailored for required keys...