Clojure defmacro loses metadata

Question

I am trying to create a little Clojure macro that defs a String with a type hint:

(defmacro def-string [name value]
  `(def ^String ~name ~value         


        

Answer 1

Metadata doesn't show up in a macroexpand since it's supposed to be "invisible".

If the macro is correct (which it isn't) you should be able to call (meta #'db-host-option) to inspect the meta data on the var.

Note that (def sym ...) inserts metadata on the var that it receives from the symbol. But ^Tag ~name sets the meta data on ~name (unquote name), not on the passed in symbol bound to name. It can't do anything else since ^Tag ... processing is done by the reader, which is already finished once macro expansion starts.

You want something like

(defmacro def-string [name value]
  `(def ~(with-meta name {:tag String}) ~value))


user> (def-string bar 1)
#'user/bar
user> (meta #'bar)
{:ns #, :name bar, :file "NO_SOURCE_FILE", :line 1, :tag java.lang.String}