Define new defn, lein uberjar succeeds to compile but lein run fails

[mattias w]

I defined my own defn in the namespace mwm.

My new code looks like this

(mwm/defn foo [x] ...)

Everything was fine as long as it was called defn2, but after renaming it to defn and refering to the original defn using clojure.core/defn, only "lein uberjar" works.

When I run "lein run", the compilation fails as

c:\data3\clojure\cdn77-purge>lein run
WARNING: defn already refers to: #'clojure.core/defn in namespace: mw.mwm, being
 replaced by: #'mw.mwm/defn
Exception in thread "main" java.lang.ClassNotFoundException: mw.mw1, compiling:(
mw/mw1.clj:40:1)
        at clojure.lang.Compiler.analyze(Compiler.java:6543)
        at clojure.lang.Compiler.analyze(Compiler.java:6485)
        at clojure.lang.Compiler$InvokeExpr.parse(Compiler.java:3791)
        at clojure.lang.Compiler.analyzeSeq(Compiler.java:6725)

The code can be found at https://github.com/mattiasw2/cdn77-purge/tree/renamed_to_defn

[mattias w]

I moved my own definition of defn to a separate project, and then it works. It seems you cannot redefine defn within the same project it is used.

[Benjamin R. Haskell]

It sounds like you're looking for refer-clojure: https://clojuredocs.org/clojure.core/refer-clojure

E.g., for your project:

(ns mw.mwm

  (:require

   [clojure.pprint :as pp]

   [clojure.walk :as walk])

  (:refer-clojure :exclude [defn])

  (:gen-class))

Tested in a fork: https://github.com/mattiasw2/cdn77-purge/compare/renamed_to_defn...benizi:fix-defn-issue

Defining your own `defn` is a fairly unorthodox thing to do.  (Usually it's less Clojure-centric names that cause problems, like `time` from the example, or `filter`, `min`, or `max`.)  Based on your comment, it seems easier to just write a different version of `get` that handles nils the way you want, instead of complicated macro behavior.  E.g.:

(defn get!   ;; "!" seems better than "?" to indicate the "dangerous" assert

  "Get a value out of a map, asserting it is non-nil"

  [from key]

  (let [val (get from key)]

    (assert (some? val) (str key " is nil"))

    val))

Seems much more straightforward than a macro that translates (:key? map) to something roughly equivalent to (get! map :key).

Best,

Ben

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