lein uberjar cannot find an implementation defined in deftype

Question

In our Clojure codebase we have a protocol:

(ns project.repository)

(defprotocol Repository
  (index [this fields unique]))

A type

(ns project.mongo (:require 
  [monger.collection :as mc] 
  [monger.core :as mg]
  [project.repository :refer :all]))  

(deftype MongoRepository [db collection-name]
  Repository
  (index [this fields unique]
    (mc/ensure-index db collection-name fields {:unique unique})))

(defn mongo-repository [db coll] (MongoRepository. db coll))

(def mongo-db ((mg/connect-via-uri "mongodb://127.0.0.1/bots") :db))

And an instantiation

(ns project.users (:require 
  [lp-bots.storages.repository :refer :all]
  [lp-bots.storages.mongo :refer [mongo-repository mongo-db]]))

(def users-storage (mongo-repository mongo-db "users"))
(index users-storage [:key1 :key2] true)

This works fine when used interactively from REPL or launched with lein run, but lein uberjar invariably throws an exception:

Exception in thread "main" java.lang.ExceptionInInitializerError, compiling:(/tmp/form-init118199196859405970.clj:1:72)
    ...
Caused by: java.lang.ExceptionInInitializerError
    ... 
Caused by: java.lang.IllegalArgumentException: No implementation of method: :index of protocol: #'project.repository/Repository found for class: project.mongo.MongoRepository
    at clojure.core$_cache_protocol_fn.invokeStatic(core_deftype.clj:568)
    at clojure.core$_cache_protocol_fn.invoke(core_deftype.clj:560)
    at project.repository$fn__557$G__514__566.invoke(repository.clj)
    at project.users__init.load(Unknown Source)
    at project.users__init.<clinit>(Unknown Source)

The weirdest part is that the problem goes away when (index) is called in a (let):

(def users-storage
  (let [u (mongo-repository mongo-db "leads")]
    (index u [:key1 :key2] true)
    u))

Any thoughts on what might be causing the difference?

Answer 1

I would suspect that it's something to do with trying to connect to MongoDB when compiling the project.mongo ns, or the project.users ns. These lines should probably be in a function call that's called at startup, rather than as the code is loaded:

(def mongo-db ((mg/connect-via-uri "mongodb://127.0.0.1/bots") :db))

and

(index users-storage [:key1 :key2] true)