Implement a let-like macro

[stathissideris]

One option would look like this:

(lens/let [{::storage [::url ::port ::password]} foo
           {::logging [::level ::destination ::type]} foo]
  (prn "level is" level)
  (prn "type is" type))

[stathissideris]

Another idea by Max Penet:

(lens/let [{:keys [::url ::port ::password] :spec ::storage} foo
           {:keys [::level ::destination ::type] :spec ::logging} foo]
  (prn "level is" level)
  (prn "type is" type))

[akovantsev]

• delegate the rest of form to clojure.core/let
• support symbols instead of keys: (lens/let [{:keys [foo bar] :spec ::baz} m])
• support of namespace on :keys instead of in vector:
  (lens/let [{::keys [:url :port :password] :spec ::storage} foo])
• maybe even replace/wrap clojure.core/let completely, and allow usual bindings as well:

(lens/let [{::storage [::url ::port ::password]} foo
           x 1])

instead of

(lens/let [{::storage [::url ::port ::password]} foo]
  (let [x 1]))

[akovantsev]

• make sure to just test whether enumerated keys belong to spec, and avoid potentially expensive validation of entire map against the spec itself (s/keys validates both: 1) keys are present, and 2) value satisfies key's spec)

[akovantsev]

• make sure aliased spec is supported:

(s/def ::m (s/keys :req [::foo]))
(s/def ::x ::m)
(lens/let [{::keys [foo] :spec ::x} ...