clj-config

pre-commit

• Install: https://pre-commit.com/
• running locally: This will also happen automatically before committing to a branch, but you can also run the tasks with pre-commit run --all-files

Environmental configuration for Clojure projects inspired by the Ruby dotenv gem. clj-config loads config values in descending order of preference from

• environmental variables
• .env.local
• .env

.env and .env.local are files in the project's root folder of the format

KEY="VALUE" # and a comment

note values must be quoted

Typically a project's repo will include .env files corresponding to each non-prod environment, i.e. .env.dev, .env.ci and .env.qa. For development, symlink an enviroment's config to .env (ln -s .env.foo .env), and override any values in .env.local (not stored in git).

Usage

Config values should be declared using the defconfig macro, and config should be initialized by calling init!, e.g.

(require '[clj-config.core :refer [defconfig init!]])

(defconfig
  :env [[foo "BAZ"]
        [bar "QUX" {:default 42
                    :parser #(Integer/parseInt %)
                    :validator #(< 13 % 100)}]]
  :app [[sentry-cfg :sentry]                                   ; grab entire map
        [sentry-url [:sentry :dsn] {:validator #"^https?://"}] ; or just bits
        [sentry-usr [:sentry :usr]]])                          ; and pieces

(init!) ;; call init! once as the app starts

;; @foo contains the value of BAZ

defconfig creates delays foo, bar, sentry-cfg, sentry-url, and sentry-usr. init! will raise an exception if an environmental var declared in defconfig isn't present.

(for :app vars, exception is raised if the app-config edn structure does not contain the keypath specified in defconfig)

Each entry in the defconfig form can be supplied with an optional map with the following keys:

Key	Type	Meaning
:default	arbitrary	Will supply the var with this value if it's not found in the environment.
:parser	function	Converts the string found in the environment into the proper data.
:validator	extender of IValidate	Examines the parsed data for correctness.

The IValidate protocol has already been extended to clojure.lang.IFn and to java.util.regex.Pattern. These types can be passed in the :validator out of the box. Functions used as validators should return a boolean.

Testing

Make a config fixture in your test namespace and call (make-config-fixture ...)

(def +my-sample-config+
  {:rabbitmq
   {:exchange
    {:mail
     {:name "Mail"
      :queues
      {:incoming {:name "message-api.mail.Incoming" :routing-key "mail.incoming"}
       :outgoing {:name "message-api.mail.Outgoing" :routing-key "mail.outgoing"}}}}}})

(use-fixtures :once
  (make-config-fixture +my-sample-config+))

app-config.edn

{:sentry-dsn {:dev           nil
              [:ci :qa]      "ci/qa sentry dsn"
              #{:production} "prod sentry dsn"  ;; infra specifies 'production'
              :default       "default dsn"}

 :web-server-threads {:dev 80
                      :ci 40
                      :qa 20
                      :production 10
                      #{:default} 4}

 :api-key "invariant"

 :nested {:url "moarcats.gov"
          :pwd "m30w"
          :usr {[:dev :ci] "mittens-dev"    ;; vectors will be coerced to sets
                #{:qa}     "mittens-qa"
                :production "mittens-prod"
                [:default] "mittens-default"}}}

;; NOTE:
;; The current version of clj-config is hard-wired to recognize :default as a fall-back.
;; This bites, and will hopefully be made open to extensibility on the next go-round.