Envy

Configuration switcher by an environment variable inspired by Perl's Config::ENV.

Usage

(defpackage :myapp.config
  (:use :cl
        :envy))
(in-package :myapp.config)

(setf (config-env-var) "APP_ENV")

(defconfig :common
  `(:application-root ,(asdf:component-pathname (asdf:find-system :myapp))))

(defconfig |development|
  '(:debug T
    :database-type :sqlite3
    :database-connection-spec (:database-name "sqlite3.db")))

(defconfig |production|
  '(:database-type :mysql
    :database-connection-spec (:database-name "test"
                               :usename "whoami"
                               :password "1234")))

(defconfig |staging|
  `(:debug T
    ,@|production|))

(defpackage :myapp
  (:use :cl)
  (:import-from :envy
                :config)
(in-package :myapp)

(getf (config :myapp.config) :database-type)

Calling APP_ENV from the command line

For example, APP_ENV=development sbcl runs a REPL process that uses development config values.

Description

Envy is a configuration manager for various applications.

Envy uses an environment variable to determine a configuration to use. I'm not sure this is ideal even for Common Lisp applications, but this can separate configuration system from an implementation.

Configurations

Normal configurations

ENVY:DEFCONFIG is a macro for defining a named configuration.

Don't forget to set (ENVY:CONFIG-ENV-VAR) which is a name of environment variable to determine a configuration.

(setf (config-env-var) "APP_ENV")

;; Use SQLite3 for development
(defconfig |development|
  '(:server :hunchentoot
    :database-type :sqlite3
    :database-connection-spec (:database-name "sqlite3.db")))

;; Use MySQL in production environment
(defconfig |production|
  '(:server :fcgi
    :database-type :mysql
    :database-connection-spec (:database-name "test"
                               :usename "whoami"
                               :password "1234")))

Merging

Each configurations are represented as property lists. It means you can merge them by the default way of merging lists -- cons, append or/and splicing unquote.

(defconfig |staging|
  `(:server :hunchentoot
    ,@|production|))

Common configurations

You can also define a common configuration which will be used by all configurations.

(defconfig :common
  `(:application-root ,(asdf:component-pathname (asdf:find-system :myapp))))

Accessing to configuration

ENVY:CONFIG is an accessor to get the current configuration.

(config :<configuration-package-name>)

(config :myapp.config)
;=> '(:server :hunchentoot
      :database-type :sqlite3
      :database-connection-spec (:database-name "sqlite3.db")
      :application-root #P"/path/to/application/")

(getf (config :myapp.config) :database-type)
;=> :sqlite3

Tips

(defpackage myapp.config
  (:use :cl
        :envy)
  (:shadow :envy
           :config)
  (:export :config))
(in-package :myapp.config)

(defconfig :common
  ...)

;;
;; ... Configurations ...
;;

(defun config ()
  (envy:config #.(package-name *package*)))

fukamachi / envy

readme