Dotenv parser rules:

• skip empty lines
• trim every string (remove all spaces before first non-whitespace char and after last non-whitespace char)
• skip commentary lines (# at the line start)
• skip lines which doesn’t look like an proper assignment
• trim variable name and its value

This package can be used as a library for manipulating .env files. Contact me if you’re making something interesting with it, I’m looking for usecases ;-).

This package is not published on Melpa yet, so you need something like quelpa to install it directly from the source repository.

(use-package dotenv
  :ensure nil
  :quelpa
  (dotenv :repo "pkulev/dotenv.el"
          :fetcher github :upgrade t))

Note that in the following examples installation-related use-package clauses are omitted.

Built-in project.el is quite neat, but has no project-switch-hook. The only solution I found is to hook on prog-mode for now, very suboptimal.

(use-package dotenv
  :hook
  (prog-mode . dotenv-update-current-env))

It doesn’t happen by default, pass t as override into dotenv-update-* function:

(use-package dotenv
  :hook
  (prog-mode . (lambda () (dotenv-update-current-env t))))

Hook for loading project’s .env (if exists) after switching project via projectile.

(use-package dotenv
  :after projectile
  :hook
  (projectile-after-switch-project-hook . (lambda () (dotenv-update-project-env (projectile-project-root)))))

In this example .env file contains PYTHONPATH among other vaiables. Assuming that PYTHONPATH contains list of pathes (delimeted by ’:’) relative to the project’s root we can transform it into absolute. To do that add to dotenv-transform-alist a pair of a predicate function and a transform function. Predicate function takes k and v and returns t or nil, transform function takes k and v and returns two-element list with new values for k and v.

(use-package dotenv
  :after projectile
  :config
  (defun dotenv-absolutify-pythonpath (k v)
    (list k (dotenv-absolutify-path-var-in-project v)))

  (add-to-list
   'dotenv-transform-alist
   '((lambda (k v) (string= k "PYTHONPATH")) . dotenv-absolutify-pythonpath))

  :hook
  (projectile-after-switch-project-hook . (lambda () (dotenv-update-project-env (projectile-project-root)))))