* lisp/files-x.el (modify-file-local-variable-message): New function.

(modify-file-local-variable)
(modify-file-local-variable-prop-line): Add arg INTERACTIVE
and call `modify-file-local-variable-message' when it's non-nil.
(add-file-local-variable, delete-file-local-variable)
(add-file-local-variable-prop-line)
(delete-file-local-variable-prop-line): Add arg INTERACTIVE and use it.

Fixes: debbugs:9820

1 files changed, 57 insertions, 18 deletions

diff --git a/lisp/files-x.el b/lisp/files-x.el
index 2ae1a0e4045..6864e9a7b14 100644
--- a/lisp/files-x.el
+++ b/lisp/files-x.el
@@ -115,7 +115,38 @@ Intended to be used in the `interactive' spec of
      ((and (stringp mode) (fboundp (intern mode))) (intern mode))
      (t mode))))
 
-(defun modify-file-local-variable (variable value op)
+(defun modify-file-local-variable-message (variable value op)
+  (let* ((not-value (make-symbol ""))
+	 (old-value (cond ((eq variable 'mode)
+			   major-mode)
+			  ((eq variable 'coding)
+			   buffer-file-coding-system)
+			  (t (if (and (symbolp variable)
+				      (boundp variable))
+				 (symbol-value variable)
+			       not-value))))
+	 (new-value (if (eq op 'delete)
+			(cond ((eq variable 'mode)
+			       (default-value 'major-mode))
+			      ((eq variable 'coding)
+			       (default-value 'buffer-file-coding-system))
+			      (t (if (and (symbolp variable)
+					  (default-boundp variable))
+				     (default-value variable)
+				   not-value)))
+		      (cond ((eq variable 'mode)
+			     (let ((string (format "%S" value)))
+			       (if (string-match-p "-mode\\'" string)
+				   value
+				 (intern (concat string "-mode")))))
+			    (t value)))))
+    (when (or (eq old-value not-value)
+	      (eq new-value not-value)
+	      (not (equal old-value new-value)))
+      (message "%s" (substitute-command-keys
+		     "For this change to take effect revisit file using \\[revert-buffer]")))))
+
+(defun modify-file-local-variable (variable value op &optional interactive)
   "Modify file-local VARIABLE in Local Variables depending on operation OP.
 
 If OP is `add-or-replace' then delete all existing settings of
@@ -198,10 +229,13 @@ from the Local Variables list ignoring the input argument VALUE."
 	   ((eq variable 'mode) (goto-char beg))
 	   ((null replaced-pos) (goto-char end))
 	   (replaced-pos (goto-char replaced-pos)))
-	  (insert (format "%s%S: %S%s\n" prefix variable value suffix)))))))
+	  (insert (format "%s%S: %S%s\n" prefix variable value suffix))))
+
+      (when interactive
+	(modify-file-local-variable-message variable value op)))))
 
 ;;;###autoload
-(defun add-file-local-variable (variable value)
+(defun add-file-local-variable (variable value &optional interactive)
   "Add file-local VARIABLE with its VALUE to the Local Variables list.
 
 This command deletes all existing settings of VARIABLE (except `mode'
@@ -213,17 +247,17 @@ 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))
+     (list variable (read-file-local-variable-value variable) t)))
+  (modify-file-local-variable variable value 'add-or-replace interactive))
 
 ;;;###autoload
-(defun delete-file-local-variable (variable)
+(defun delete-file-local-variable (variable &optional interactive)
   "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))
+   (list (read-file-local-variable "Delete file-local variable") t))
+  (modify-file-local-variable variable nil 'delete interactive))
 
-(defun modify-file-local-variable-prop-line (variable value op)
+(defun modify-file-local-variable-prop-line (variable value op &optional interactive)
   "Modify file-local VARIABLE in the -*- line depending on operation OP.
 
 If OP is `add-or-replace' then delete all existing settings of
@@ -261,11 +295,11 @@ from the -*- line ignoring the input argument VALUE."
 		  (looking-at "<\\?xml[^>\n]*>$"))
 	  (forward-line 1))
 
-	(comment-normalize-vars)
 	(let ((comment-style 'plain)
 	      (comment-start (or comment-start ";;; "))
 	      (line-beg (line-beginning-position))
 	      (ce nil))
+	  (comment-normalize-vars)
 	  ;; If the first line contains a comment.
 	  (if (save-excursion
 		(and (looking-at comment-start-skip)
@@ -337,14 +371,19 @@ from the -*- line ignoring the input argument VALUE."
 	   ((null replaced-pos) (goto-char end))
 	   (replaced-pos (goto-char replaced-pos)))
 	  (if (and (not (eq (char-before) ?\;))
-		   (not (equal (point) (marker-position beg))))
+		   (not (equal (point) (marker-position beg)))
+		   ;; When existing `-*- -*-' is empty, beg > end.
+		   (not (> (marker-position beg) (marker-position end))))
 	      (insert ";"))
 	  (unless (eq (char-before) ?\s) (insert " "))
 	  (insert (format "%S: %S;" variable value))
-	  (unless (eq (char-after) ?\s) (insert " "))))))))
+	  (unless (eq (char-after) ?\s) (insert " ")))))
+
+      (when interactive
+	(modify-file-local-variable-message variable value op)))))
 
 ;;;###autoload
-(defun add-file-local-variable-prop-line (variable value)
+(defun add-file-local-variable-prop-line (variable value &optional interactive)
   "Add file-local VARIABLE with its VALUE to the -*- line.
 
 This command deletes all existing settings of VARIABLE (except `mode'
@@ -355,15 +394,15 @@ If there is no -*- line at the beginning of the current file buffer
 then this function adds it."
   (interactive
    (let ((variable (read-file-local-variable "Add -*- file-local variable")))
-     (list variable (read-file-local-variable-value variable))))
-  (modify-file-local-variable-prop-line variable value 'add-or-replace))
+     (list variable (read-file-local-variable-value variable) t)))
+  (modify-file-local-variable-prop-line variable value 'add-or-replace interactive))
 
 ;;;###autoload
-(defun delete-file-local-variable-prop-line (variable)
+(defun delete-file-local-variable-prop-line (variable &optional interactive)
   "Delete all settings of file-local VARIABLE from the -*- line."
   (interactive
-   (list (read-file-local-variable "Delete -*- file-local variable")))
-  (modify-file-local-variable-prop-line variable nil 'delete))
+   (list (read-file-local-variable "Delete -*- file-local variable") t))
+  (modify-file-local-variable-prop-line variable nil 'delete interactive))
 
 (defvar auto-insert) ; from autoinsert.el