edn-env

A small library to overlay environment variables onto a config

Why?

This library is influenced greatly by my use of cprop (which is a wonderful library, you should check it out). Praises aside, cprop makes some assumptions about values that complicates usage and has some clunky handling of resources.

edn-env aims to fix these issues by:

• assuming everything in the environment is EDN, pure and simple
• forcing the user to implement any complicated resource loading

These two points make edn-env small and flexible.

Usage

To start:

(require '[edn-env.core :as env])

overlay

The main fn provided is the overlay function which takes in a map and applies any environment variables that are contained in the given map:

;; Given this env:
;;   DATABASE__HOST=localhost
;;   DATABASE__PASSWORD=insecure
(env/overlay {:database {:host nil
                         :username "user"
                         :password nil}})
{:database
 {:host "localhost", :username "user", :password "insecure"}}

overlay can also take an options map which change its behavior:

• kebab-re: a regex whose matches will be replaced with -
• nest-re: a regex whose matches will be used to split the environment variable's name into a sequence suitable for get-in, et al.
• path-fn: is called for every element in the sequence created by nest-re.

;; Given this (arbitrary and super confusing yet explanatory) env:
;;   CLUSTERSv0vHOST.NAME=localhost
(env/overlay {:clusters [{:host-name nil}]
             {:kebab-re #"\."
              :nest-re #"v"
              :path-fn #(try
                          (Integer/parseInt %)
                          (catch Exception _
                            (keyword %)))}
{:clusters [{:host-name "localhost"}]}

load-config

Loads the given resource (defaulting to config.edn) and calls overlay on the loaded config:

;; config.edn
{:test-value nil}

;; Given this env:
;;   TEST_VALUE=420
(edn/load-config)
{:test-value 420}

load-config can also take the same options map overlay does:

;; clusters.edn
{:clusters [{:host-name nil}]}

;; It's me again!:
;;   CLUSTERSv0vHOST.NAME=localhost
(env/load-config "cluster.edn" {:kebab-re #"\."
                                :nest-re #"v"
                                :path-fn #(try
                                            (Integer/parseInt %)
                                            (catch Exception _
                                              (keyword %)))}
{:clusters [{:host-name "localhost"}]}

Contributing

Issues and PRs are welcome.