spec for a multi-arity function

[Peter Hull]

Is there any guidance on how to do the fdef for a function with more than one arity? As an example, this one which takes one or two arguments:

(defn report
  "Report an error code, optionally with a message"
  ([errno] ...)
  ([errno msg] ...))

Could be:

(s/fdef report
        :args (s/alt :brief (s/cat :errno integer?)
                     :full (s/cat :errno integer? :msg string?)))

or:

(s/fdef report
        :args (s/cat :errno integer? :msg (s/? string?)))

Some options make more sense than others, depending on the function. For example clojure.core/map is defined with five separate arities but I don't think it would be right to spec it as an alt with five alternatives, since they are all covered by "function followed by zero or more colls"

So, has a convention been established on how best to do it?

[Alex Miller]

On Thursday, October 5, 2017 at 2:02:10 PM UTC-5, Peter Hull wrote:

Is there any guidance on how to do the fdef for a function with more than one arity? As an example, this one which takes one or two arguments:

The regex specs can cover multiple options via ?, *, etc.

 

(defn report
  "Report an error code, optionally with a message"
  ([errno] ...)
  ([errno msg] ...))

So you want:

(s/fdef report

  :args (s/cat :errno int? :msg (s/? string?)))

[Alex Miller]

I should also mention that the s/alt one is fine too, but in general I find receiving the same conformed map in either case but with keys either present or absent works better with all your typical Clojure destructuring etc so I prefer the s/? version.