[Misc] Enable ‘lispy’ only when available

To ensure that Emacs is still largely responsive without it.

init.el

@@ -133,9 +133,11 @@
   (add-hook 'after-save-hook 'executable-make-buffer-file-executable-if-script-p)
   (add-hook 'text-mode-hook 'turn-on-auto-fill)
   (add-hook 'prog-mode-hook 'page-break-lines-mode)
+  (add-hook 'lisp-mode-hook 'turn-on-lispy-when-available)
+
   (when (<= 24 emacs-major-version)
     (add-hook 'prog-mode-hook 'electric-indent-local-mode))
-  (add-hook 'lisp-mode-hook 'lispy-mode)
+
   (unless (eq system-type 'windows-nt)
     ;; flyspell doesn’t work on windows right now, need to further investigate
     ;; what is happening here
@@ -544,6 +546,7 @@ search commands like `db/helm-shortcuts’."
              db/hex-to-ascii
              db/ascii-to-hex
              conditionally-enable-lispy
+             turn-on-lispy-when-available
              db/sort-nsm-permanent-settings
              db/update-cert-file-directory
              endless/colorize-compilation
@@ -2201,7 +2204,7 @@ search commands like `db/helm-shortcuts’."
 (use-package elisp-mode
   :defer t
   :config (progn
-            (add-hook 'emacs-lisp-mode-hook 'lispy-mode)
+            (add-hook 'emacs-lisp-mode-hook 'turn-on-lispy-when-available)
             (add-hook 'emacs-lisp-mode-hook 'db/add-use-package-to-imenu)))
 
 (use-package geiser
@@ -2225,7 +2228,7 @@ search commands like `db/helm-shortcuts’."
               cider-cljs-lein-repl "(cemerick.piggieback/cljs-repl (cljs.repl.rhino/repl-env))")
   :config (progn
             (add-hook 'cider-repl-mode-hook 'subword-mode)
-            (add-hook 'cider-repl-mode-hook 'lispy-mode)
+            (add-hook 'cider-repl-mode-hook 'turn-on-lispy-when-available)
             (add-hook 'cider-repl-mode-hook 'cider-repl-toggle-pretty-printing)
             (add-hook 'cider-repl-mode-hook 'company-mode)))
 
@@ -2236,7 +2239,7 @@ search commands like `db/helm-shortcuts’."
               (forall 'defun)
               (exists 'defun)
               (dopar 'defun))
-            (add-hook 'clojure-mode-hook 'lispy-mode)
+            (add-hook 'clojure-mode-hook 'turn-on-lispy-when-available)
             (add-hook 'clojure-mode-hook 'clj-refactor-mode)
             (add-hook 'clojure-mode-hook 'yas-minor-mode)
             (add-hook 'clojure-mode-hook 'company-mode)))
@@ -2269,7 +2272,7 @@ search commands like `db/helm-shortcuts’."
 (use-package hy-mode
   :commands (hy-mode)
   :config (progn
-            (add-hook 'hy-mode-hook 'lispy-mode)
+            (add-hook 'hy-mode-hook 'turn-on-lispy-when-available)
             (add-hook 'hy-mode-hook 'inferior-lisp)))
 
 

site-lisp/db-utils.el

@@ -226,6 +226,14 @@ lispy."
                  (eq this-command 'pp-eval-expression)))
     (lispy-mode 1)))
 
+(defun turn-on-lispy-when-available ()
+  "Activate `lispy’ in current buffer when possible.
+Will print a warning in case of failure."
+  (interactive)
+  (with-demoted-errors "Cannot activate lispy: %s"
+    (require 'lispy)
+    (lispy-mode)))
+
 (defun db/sort-nsm-permanent-settings ()
   "Sort values in `nsm-permanent-host-settings’."
   (setq nsm-permanent-host-settings