Re: Add file-locals and dir-locals

[Juri Linkov <juri@jurta.org>]

> I don't quite catch the idea behind
>
> 		  (and (search-backward "Local Variables:" nil t)
> 		       (search-forward "Local Variables:" nil t)))
>
> Do you search the entire buffer here?

I had the same doubt that this is sub-ideal.  Thanks, fixed.

> Also I didn't find a functionality to remove the headers and trailers as
> soon as all settings have been removed.

I intentionally omitted this functionality because I think it should
leave a harmless empty placeholder for the user's convenience.

Below is the final patch that I find useful enough to commit.
I invite you and other developers to improve this further as you wish.

Index: etc/TODO
===================================================================
RCS file: /sources/emacs/emacs/etc/TODO,v
retrieving revision 1.205
diff -u -r1.205 TODO
--- etc/TODO	18 Jul 2009 21:04:15 -0000	1.205
+++ etc/TODO	19 Jul 2009 18:05:50 -0000
@@ -202,9 +202,6 @@
 ** Implement something better than the current Refill mode.  This
   probably needs some primitive support.
 
-** Add a command to make a "Local Variables" section in the current buffer
-  and/or add a variable to the list.
-
 ** Implement primitive and higher-level functions to allow filling
   properly with variable-pitch faces.
 
Index: etc/NEWS
===================================================================
RCS file: /sources/emacs/emacs/etc/NEWS,v
retrieving revision 1.2046
diff -c -r1.2046 NEWS
*** etc/NEWS	19 Jul 2009 00:29:52 -0000	1.2046
--- etc/NEWS	19 Jul 2009 18:05:32 -0000
***************
*** 58,63 ****
--- 58,72 ----
  `process-kill-buffer-query-function' from `kill-buffer-query-functions' or
  setting the appropriate process flag with `set-process-query-on-exit-flag'.
  
+ ** New command to add a file-local variable to the "Local Variables" list
+ in the current buffer is `add-file-local-variable'.  New command to remove
+ a file-local variable from the "Local Variables" list is
+ `delete-file-local-variable'.  New commands to add/remove
+ a directory-local variable to/from the .dir-locals.el file are
+ `add-dir-local-variable' and `delete-dir-local-variable'.  New commands to
+ copy file-local variables to directory-local variables and vice versa are
+ `copy-file-locals-to-dir-locals' and `copy-dir-locals-to-file-locals'.
+ 
  \f
  * Changes in Specialized Modes and Packages in Emacs 23.2
  
Index: lisp/files.el
===================================================================
RCS file: /sources/emacs/emacs/lisp/files.el,v
retrieving revision 1.1059
diff -c -r1.1059 files.el
*** lisp/files.el	19 Jul 2009 16:55:16 -0000	1.1059
--- lisp/files.el	19 Jul 2009 18:04:44 -0000
***************
*** 3407,3412 ****
--- 3407,3699 ----
  	    (hack-local-variables-filter variables dir-name)))))))
  
  \f
+ ;;; Commands to add/delete file-local/directory-local variables.
+ 
+ (defun read-file-local-variable (prompt)
+   "Read file-local variable using PROMPT and completion.
+ Intended to be used in the `interactive' spec of
+ `add-file-local-variable', `delete-file-local-variable',
+ `add-dir-local-variable', `delete-dir-local-variable'."
+   (let (default variable)
+     (setq default (variable-at-point))
+     (setq default (and (symbolp default) (boundp default)
+ 		       (symbol-name default)))
+     (setq variable
+ 	  (completing-read
+ 	   (if default
+ 	       (format "%s (default %s): " prompt default)
+ 	     (format "%s: " prompt))
+ 	   obarray
+ 	   (lambda (sym)
+ 	     (or (user-variable-p sym)
+ 		 (memq sym '(mode eval coding unibyte))))
+ 	   nil nil nil default nil))
+     (and (stringp variable) (intern variable))))
+ 
+ (defun read-file-local-variable-value (variable)
+   "Read value of file-local VARIABLE using completion.
+ Intended to be used in the `interactive' spec of
+ `add-file-local-variable' and `add-dir-local-variable'."
+   (let (default value)
+     (cond
+      ((eq variable 'mode)
+       (setq default (and (symbolp major-mode) (symbol-name major-mode)))
+       (setq value
+ 	    (completing-read
+ 	     (if default
+ 		 (format "Add %s with value (default %s): " variable default)
+ 	       (format "Add %s with value: " variable))
+ 	     obarray
+ 	     (lambda (sym)
+ 	       (and (string-match-p "-mode\\'" (symbol-name sym))
+ 		    (not (string-match-p "-minor-mode\\'" (symbol-name sym)))))
+ 	     nil nil nil default nil))
+       (and (stringp value)
+ 	   (intern (replace-regexp-in-string "-mode\\'" "" value))))
+      ((eq variable 'eval)
+       (let ((minibuffer-completing-symbol t))
+ 	(read-from-minibuffer (format "Add %s with expression: " variable)
+ 			      nil read-expression-map t
+ 			      'read-expression-history)))
+      ((eq variable 'coding)
+       (setq default (and (symbolp buffer-file-coding-system)
+ 			 (symbol-name buffer-file-coding-system)))
+       (read-coding-system
+        (if default
+ 	   (format "Add %s with value (default %s): " variable default)
+ 	 (format "Add %s with value: " variable))
+        default))
+      (t
+       (read (read-string (format "Add %s with value: " variable)
+ 			 nil 'set-variable-value-history
+ 			 (format "%S" (symbol-value variable))))))))
+ 
+ (defun read-file-local-variable-mode ()
+   "Read per-directory file-local variable's mode using completion.
+ Intended to be used in the `interactive' spec of
+ `add-dir-local-variable', `delete-dir-local-variable'."
+   (let* ((default (and (symbolp major-mode) (symbol-name major-mode)))
+ 	 (mode
+ 	  (completing-read
+ 	   (if default
+ 	       (format "Mode or subdirectory (default %s): " default)
+ 	     (format "Mode or subdirectory: "))
+ 	   obarray
+ 	   (lambda (sym)
+ 	     (and (string-match-p "-mode\\'" (symbol-name sym))
+ 		  (not (string-match-p "-minor-mode\\'" (symbol-name sym)))))
+ 	   nil nil nil default nil)))
+     (cond
+      ((equal mode "nil") nil)
+      ((and (stringp mode) (fboundp (intern mode))) (intern mode))
+      (t mode))))
+ 
+ (defun modify-file-local-variable (variable value op)
+   "Modify file-local VARIABLE in Local Variables depending on operation OP.
+ 
+ If OP is `add-or-replace' then delete all existing settings of
+ VARIABLE (except `eval') and add a new file-local VARIABLE with VALUE
+ to the Local Variables list.
+ 
+ If there is no Local Variables list in the current file buffer and OP
+ is not `delete' then this function adds the first line containing the
+ string `Local Variables:' and the last line containing the string `End:'.
+ 
+ If OP is `delete' then delete all existing settings of VARIABLE
+ from the Local Variables list ignoring the input argument VALUE."
+   (catch 'exit
+     (let ((startpos (point)) endpos replaced-p)
+       (unless enable-local-variables
+ 	(throw 'exit (message "File-local variables are disabled")))
+ 
+       ;; Look for "Local variables:" line in last page.
+       (goto-char (point-max))
+       (search-backward "\n\^L" (max (- (point-max) 3000) (point-min))
+ 		       'move)
+ 
+       ;; Add "Local variables:" list if not found.
+       (unless (let ((case-fold-search t))
+ 		(search-forward "Local Variables:" nil t))
+ 
+ 	;; Don't add "Local variables:" list for the deletion operation.
+ 	(when (eq op 'delete)
+ 	  (throw 'exit (progn (goto-char startpos)
+ 			      (message "Local Variables not found"))))
+ 
+ 	(goto-char (point-max))
+ 	(let ((comment-style 'plain)
+ 	      (comment-start (or comment-start ";;; ")))
+ 	  (comment-region
+ 	   (prog1 (setq startpos (point))
+ 	     (insert "\nLocal Variables:\nEnd:\n"))
+ 	   (point)))
+ 
+ 	(unless (let ((case-fold-search t))
+ 		  (goto-char startpos)
+ 		  (search-forward "Local Variables:" nil t))
+ 	  (throw 'exit (message "Can't add file-local variables"))))
+ 
+       ;; suffix is what comes after "local variables:" in its line.
+       ;; prefix is what comes before "local variables:" in its line.
+       (let* ((suffix (buffer-substring (point) (line-end-position)))
+ 	     (prefix (buffer-substring (line-beginning-position)
+ 				       (match-beginning 0)))
+ 	     (suffix-re (concat (regexp-quote suffix) "$"))
+ 	     (prefix-re (concat "^" (regexp-quote prefix))))
+ 
+ 	;; Find or add missing "End:".
+ 	(forward-line 1)
+ 	(setq startpos (point))
+ 	(save-excursion
+ 	  (unless (let ((case-fold-search t))
+ 		    (re-search-forward
+ 		     (concat prefix-re "[ \t]*End:[ \t]*" suffix-re)
+ 		     nil t))
+ 	    (save-excursion
+ 	      (insert (format "%sEnd:%s\n" prefix suffix))))
+ 	  (beginning-of-line)
+ 	  (setq endpos (point-marker)))
+ 
+ 	;; Find and delete all existing variable/value pairs.
+ 	(when (member op '(add-or-replace delete))
+ 	  (if (and (eq variable 'eval) (eq op 'add-or-replace))
+ 	      (goto-char endpos)
+ 	    (goto-char startpos)
+ 	    (while (re-search-forward
+ 		    (format "%s%S:.*%s" prefix-re variable suffix-re) endpos t)
+ 	      (delete-region (match-beginning 0) (1+ (match-end 0)))
+ 	      (setq replaced-p t))))
+ 
+ 	;; Add a new variable/value pair.  Add `mode' to the start, add new
+ 	;; variable to the end, and add a replaced variable to its last location.
+ 	(when (eq op 'add-or-replace)
+ 	  (cond
+ 	   ((eq variable 'mode) (goto-char startpos))
+ 	   ((null replaced-p) (goto-char endpos)))
+ 	  (insert (format "%s%S: %S%s\n" prefix variable value suffix)))))))
+ 
+ (defun add-file-local-variable (variable value)
+   "Add file-local VARIABLE with its VALUE to the Local Variables list.
+ 
+ This command deletes all existing settings of VARIABLE (except `eval')
+ and adds a new file-local VARIABLE with VALUE to the Local Variables list.
+ 
+ If there is no Local Variables list in the current file buffer
+ then this function adds the first line containing the string
+ `Local Variables:' and the last line containing the string `End:'."
+   (interactive
+    (let ((variable (read-file-local-variable "Add file-local variable")))
+      (list variable (read-file-local-variable-value variable))))
+   (modify-file-local-variable variable value 'add-or-replace))
+ 
+ (defun delete-file-local-variable (variable)
+   "Delete all settings of file-local VARIABLE from the Local Variables list."
+   (interactive
+    (list (read-file-local-variable "Delete file-local variable")))
+   (modify-file-local-variable variable nil 'delete))
+ 
+ (defun modify-dir-local-variable (mode variable value op)
+   "Modify directory-local VARIABLE in .dir-locals.el depending on operation OP.
+ 
+ If OP is `add-or-replace' then delete all existing settings of
+ VARIABLE (except `eval') and add a new directory-local VARIABLE with VALUE
+ to the MODE alist where MODE can be a mode name symbol or a subdirectory name.
+ 
+ If .dir-locals.el was not found and OP is not `delete' then create
+ this file in the current directory.
+ 
+ If OP is `delete' then delete all existing settings of VARIABLE
+ from the the MODE alist ignoring the input argument VALUE."
+   (catch 'exit
+     (let (replaced-p)
+       (unless enable-local-variables
+ 	(throw 'exit (message "Directory-local variables are disabled")))
+ 
+       (let ((variables-file (or (and (buffer-file-name)
+ 				     (not (file-remote-p (buffer-file-name)))
+ 				     (dir-locals-find-file (buffer-file-name)))
+ 				dir-locals-file))
+ 	    variables)
+ 
+ 	;; Don't create ".dir-locals.el" for the deletion operation.
+ 	(when (and (eq op 'delete)
+ 		   (not (file-exists-p variables-file)))
+ 	  (throw 'exit (message "File .dir-locals.el not found")))
+ 
+ 	(let ((auto-insert nil))
+ 	  (find-file variables-file))
+ 	(goto-char (point-min))
+ 
+ 	;; Read alist of directory-local variables.
+ 	(ignore-errors
+ 	  (delete-region
+ 	   (prog1 (point)
+ 	     (setq variables (let ((read-circle nil))
+ 			       (read (current-buffer)))))
+ 	   (point)))
+ 
+ 	;; Add or replace variable in alist of directory-local variables.
+ 	(let ((mode-assoc (assoc mode variables)))
+ 	  (if mode-assoc
+ 	      (setq variables
+ 		    (cons (cons mode
+ 				(if (eq op 'delete)
+ 				    (assq-delete-all variable (cdr mode-assoc))
+ 				  (cons
+ 				   (cons variable value)
+ 				   (if (eq variable 'eval)
+ 				       (cdr mode-assoc)
+ 				     (assq-delete-all variable (cdr mode-assoc))))))
+ 			  (assq-delete-all mode variables)))
+ 	    (setq variables
+ 		  (cons `(,mode . ((,variable . ,value)))
+ 			variables))))
+ 
+ 	;; Insert modified alist of directory-local variables.
+ 	(insert ";;; Directory Local Variables\n")
+ 	(insert ";;; See (info \"(emacs) Directory Variables\")\n\n")
+ 	(pp (sort variables
+ 		  (lambda (a b)
+ 		    (cond
+ 		     ((null (car a)) t)
+ 		     ((null (car b)) nil)
+ 		     ((and (symbolp (car a)) (stringp (car b))) t)
+ 		     ((and (symbolp (car b)) (stringp (car a))) nil)
+ 		     (t (string< (car a) (car b))))))
+ 	    (current-buffer))))))
+ 
+ (defun add-dir-local-variable (mode variable value)
+   "Add directory-local VARIABLE with its VALUE and MODE to .dir-locals.el."
+   (interactive
+    (let (variable)
+      (list
+       (read-file-local-variable-mode)
+       (setq variable (read-file-local-variable "Add directory-local variable"))
+       (read-file-local-variable-value variable))))
+   (modify-dir-local-variable mode variable value 'add-or-replace))
+ 
+ (defun delete-dir-local-variable (mode variable)
+   "Delete all MODE settings of file-local VARIABLE from .dir-locals.el."
+   (interactive
+    (list
+     (read-file-local-variable-mode)
+     (read-file-local-variable "Delete directory-local variable")))
+   (modify-dir-local-variable mode variable nil 'delete))
+ 
+ (defun copy-file-locals-to-dir-locals ()
+   "Copy file-local variables to .dir-locals.el."
+   (interactive)
+   (dolist (elt file-local-variables-alist)
+     (unless (assq (car elt) dir-local-variables-alist)
+       (add-dir-local-variable major-mode (car elt) (cdr elt)))))
+ 
+ (defun copy-dir-locals-to-file-locals ()
+   "Copy directory-local variables to the Local Variables list."
+   (interactive)
+   (dolist (elt dir-local-variables-alist)
+     (add-file-local-variable (car elt) (cdr elt))))
+ 
+ \f
  (defcustom change-major-mode-with-file-name t
    "Non-nil means \\[write-file] should set the major mode from the file name.
  However, the mode will not be changed if

-- 
Juri Linkov
http://www.jurta.org/emacs/