feat(emacs/lean-require): check lean-mode dependencies in initialization

Close #91

src/emacs/lean-mode.el

@@ -10,18 +10,10 @@
 ;; Version: 0.1
 ;; URL: https://github.com/leanprover/lean/blob/master/src/emacs
 ;;
-;;
 ;; Released under Apache 2.0 license as described in the file LICENSE.
 ;;
-;;
-
-(require 'cl-lib)
+(require 'lean-require)
 (require 'eri)
-(require 'generic-x)
-(require 'compile)
-(require 'flymake)
-(require 'dash)
-(require 'dash-functional)
 (require 'lean-variable)
 (require 'lean-util)
 (require 'lean-settings)

src/emacs/lean-require.el

@@ -0,0 +1,33 @@
+;; Copyright (c) 2014 Microsoft Corporation. All rights reserved.
+;; Released under Apache 2.0 license as described in the file LICENSE.
+;;
+;; Author: Soonho Kong
+;;
+(defun lean-mode-require-package (pkg)
+  "Check whether pkg is available or not."
+  (unless (featurep pkg)
+    (if (not (require pkg (symbol-name pkg) t))
+        (error "lean-mode: required package '%s' is not found." (symbol-name pkg))
+      (message "lean-mode: package %S loaded." pkg))))
+
+(defun lean-mode-check-package (pkg)
+  "Check whether pkg is available or not."
+  (unless (featurep pkg)
+    (if (not (require pkg (symbol-name pkg) t))
+        (message "lean-mode: optional package '%s' is not found." (symbol-name pkg))
+      (message "lean-mode: optional package %S loaded." pkg))))
+
+(defun lean-mode-check-requirements ()
+  "Check lean-mode requirements"
+  (if (not (>= emacs-major-version 24))
+      (error "Emacs version >= 24 is required to use lean-mode"))
+  (lean-mode-check-package 'package)
+  (lean-mode-check-package 'dash)
+  (let ((required-packages '(cl-lib dash dash-functional flymake compile s))
+        (optional-packages '(flycheck whitespace-cleanup-mode fill-column-indicator
+				      lua-mode mmm-mode)))
+    (-each required-packages 'lean-mode-require-package)
+    (-each optional-packages 'lean-mode-check-package)))
+
+(lean-mode-check-requirements)
+(provide 'lean-require)