Merge pull request #2 from jimeh/setup-advice-on-first-use

yank-indent.el

@@ -109,6 +109,37 @@ from having `yank-indent-mode' enabled."
        (or (member major-mode yank-indent-exact-modes)
            (apply #'derived-mode-p yank-indent-derived-modes))))
 
+(defvar yank-indent--initial-setup nil)
+
+(defun yank-indent--is-setup-p ()
+  "Return non-nil if required advice is setup."
+  (and (advice-member-p #'yank-indent--after-yank-advice #'yank)
+       (advice-member-p #'yank-indent--after-yank-advice #'yank-pop)))
+
+;;;###autoload
+(defun yank-indent-setup ()
+  "Setup advice on `yank' and `yank-pop' as required by `yank-indent-mode'.
+
+First time `yank-indent-mode' is enabled it will automatically
+call `yank-indent-setup' if needed.
+
+Setup can be undone with `yank-indent-teardown', but enabling
+`yank-indent-mode' again after that will not run setup again."
+  (interactive)
+  (advice-add #'yank :after #'yank-indent--after-yank-advice)
+  (advice-add #'yank-pop :after #'yank-indent--after-yank-advice)
+  (setq yank-indent--initial-setup t))
+
+;;;###autoload
+(defun yank-indent-teardown ()
+  "Undo `yank-indent-setup' by removing advice from `yank' and `yank-pop'.
+
+If this is used, `yank-indent-setup' must be explicitly called
+before `yank-indent-mode' will work again."
+  (interactive)
+  (advice-remove #'yank #'yank-indent--after-yank-advice)
+  (advice-remove #'yank-pop #'yank-indent--after-yank-advice))
+
 ;;;###autoload
 (define-minor-mode yank-indent-mode
   "Minor mode for automatically indenting yanked text.
@@ -117,17 +148,23 @@ When enabled, this mode indents the yanked region according to
 the current mode's indentation rules, provided that the region
 size is less than or equal to `yank-indent-threshold' and no
 prefix argument is given during yanking."
-  :lighter " YI")
-
-(defun yank-indent--enable ()
-  "Enable `yank-indent-mode' if the current buffer meets the criteria."
-  (when (yank-indent--should-enable-p)
-    (yank-indent-mode 1)))
+  :lighter " YI"
+  :group 'yank-indent
+  (if yank-indent-mode
+      ;; Auto-run advice setup if needed first time mode is enabled. Display
+      ;; warning if advice setup has been undone.
+      (when (not (yank-indent--is-setup-p))
+        (if yank-indent--initial-setup
+            (message (concat "Warning: yank-indent-mode not available, "
+                             "run `M-x yank-indent-setup' to setup."))
+          (yank-indent-setup)))))
 
 ;;;###autoload
 (define-globalized-minor-mode global-yank-indent-mode
   yank-indent-mode
-  yank-indent--enable)
+  (lambda ()
+    (when (yank-indent--should-enable-p)
+        (yank-indent-mode 1))))
 
 (defun yank-indent--after-yank-advice (&optional _)
   "Conditionally indent the region (yanked text) after yanking.
@@ -150,8 +187,5 @@ functions."
         (if (<= (- end beg) yank-indent-threshold)
             (indent-region beg end)))))
 
-(advice-add #'yank :after #'yank-indent--after-yank-advice)
-(advice-add #'yank-pop :after #'yank-indent--after-yank-advice)
-
 (provide 'yank-indent)
 ;;; yank-indent.el ends here