duplicate work in deref-input-signals

[mhuebert]

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In https://github.com/Day8/re-frame/blob/master/src/re_frame/subs.cljc#L188, the work of traversing & dereferencing is being done twice. It looks like the purpose of the inner cond form is to print a warning if an unexpected argument is passed in. Maybe we could move this check into the :else clause of map-signals, and allow for elision in prod? along the lines of:

(defn map-signals
  "Runs f over signals. Signals may take several
  forms, this function handles all of them."
  [f signals]
  (cond
    (sequential? signals) (map f signals)
    (map? signals) (map-vals f signals)
    (deref? signals) (f signals)
    :else (do (when debug-enabled?
                (console :error "re-frame: in the reg-sub for" query-id ", the input-signals function returns:" signals))
              '())))

[danielcompton]

Thanks for catching this, it does look like a bug.

In https://github.com/Day8/re-frame/commit/64f858c4e33f68b1da5d6f9532defd8a73345b0b I extracted part of deref-input-signals into map-signals so that I could reuse the same mapping logic when tracing the signals.

There was a bug in that code though, and I fixed it in https://github.com/Day8/re-frame/commit/1e82e55aa083ffac3016f54fac744ffcb417e557. However, that also introduced unnecessary derefs that weren't actually used, except for the side-effects of logging the error. The second set of derefs can be removed, we just need to find the right place and conditions for the logging statement to run.