Installing dart mode manually

If you would like to try a version other than that provided by melpa or melpa-stable (master and last tagged version respectively), you can clone the git repo. You’ll also need to install s, dash and optionally flycheck. You can still do that with package.el and melpa/melpa-stable if you prefer.

cd ~/.emacs.d/lisp
git clone https://github.com/bradyt/dart-mode.git

(setq package-archives
      '(("gnu" . "https://elpa.gnu.org/packages/")
        ("melpa" . "https://melpa.org/packages/")))
(package-initialize)
(let ((pkgs-to-install (seq-remove 'package-installed-p '(dash flycheck s))))
  (when pkgs-to-install
    (package-refresh-contents)
    (dolist (pkg pkgs-to-install)
      (package-install pkg))))

(add-to-list 'load-path "~/.emacs.d/lisp/dart-mode/")
(add-to-list 'auto-mode-alist '("\\.dart\\'" . dart-mode))
(require 'dart-mode)