Emacs $PATH

The following configuration enables Emacs to inherit the correct $PATH from the shell in all cases:

• M-x describe-variable: exec-path
• M-x eval-expression: (getenv "PATH")
• M-x shell-command: echo $PATH
• M-x compile: echo $PATH

My shell is located at /run/current-system/sw/bin/fish, so the configuration is:

(use-package exec-path-from-shell
  :pin nongnu
  :if (memq window-system '(mac ns x))
  :init
  (setq shell-file-name "/run/current-system/sw/bin/fish")
  :config
  (dolist (var '("__fish_nixos_env_preinit_sourced"
                 "__NIX_DARWIN_SET_ENVIRONMENT_DONE"
                 "__HM_SESS_VARS_SOURCED"))
    (add-to-list 'exec-path-from-shell-variables var))
  (exec-path-from-shell-initialize))

(use-package envrc
  :pin melpa
  :hook (after-init . envrc-global-mode))

• shell-file-name specifies the shell for commands like shell-command and start-process, it uses your system’s default shell by default.
• exec-path-from-shell-shell-name specifies the shell that exec-path-from-shell uses to retrieve the $PATH environment variable, it falls back to shell-file-name.
• exec-path-from-shell-variables is recommended to set if you use Direnv + HomeManager + Fish (via).