bug#20386: 25.0.50; error when calling sgml-attributes and sgml-tag

[Harald Hanche-Olsen <hanche@math.ntnu.no>]

Since I get bitten by this bug regularly, and little has happened to it, 
I took it upon myself to suggest a patch. I include it below.

I believe the patch is sufficiently small and trivial to not be “legally 
significant” (I don't have any signed papers on file).

One caveat:
This will break skeleton-read for code that calls it with a symbol, 
expecting the symbol to be evaluated, if the symbol also has a function 
binding.

If this is undesirable, replace (functionp prompt) in the patched 
skeleton-read with (and (functionp prompt) (not (symbolp prompt))).

– Harald

 From 1d8cc12f73b6b7fe7907073e6c34b558cc4f726b Mon Sep 17 00:00:00 2001
From: Harald Hanche-Olsen <hanche@math.ntnu.no>
Date: Thu, 23 Jul 2015 18:09:44 +0200
Subject: [PATCH] Fix bug #20386

---
  lisp/skeleton.el            | 17 ++++++++++-------
  lisp/textmodes/sgml-mode.el | 14 +++++++++-----
  2 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/lisp/skeleton.el b/lisp/skeleton.el
index d23488b..2c017dd 100644
--- a/lisp/skeleton.el
+++ b/lisp/skeleton.el
@@ -277,7 +277,8 @@ When done with skeleton, but before going back to 
`_'-point call
  (defun skeleton-read (prompt &optional initial-input recursive)
    "Function for reading a string from the minibuffer within skeletons.

-PROMPT must be a string or a form that evaluates to a string.
+PROMPT must be a string or a function that evaluates to a string.
+It may also be a form that evaluates to a string (deprecated).
  It may contain a `%s' which will be replaced by `skeleton-subprompt'.
  If non-nil second arg INITIAL-INPUT or variable `input' is a string or
  cons with index to insert before reading.  If third arg RECURSIVE is 
non-nil
@@ -306,12 +307,14 @@ automatically, and you are prompted to fill in the 
variable parts.")))
  	;; before point.
          (save-excursion (insert "\n")))
      (unwind-protect
-	(setq prompt (if (stringp prompt)
-			 (read-string (format prompt skeleton-subprompt)
-				      (setq initial-input
-					    (or initial-input
-						(symbol-value 'input))))
-		       (eval prompt)))
+	(setq prompt (cond ((stringp prompt)
+                            (read-string (format prompt skeleton-subprompt)
+                                         (setq initial-input
+                                               (or initial-input
+                                                   (symbol-value 
'input)))))
+                           ((functionp prompt)
+                            (funcall prompt))
+                           (t (eval prompt))))
        (or eolp
  	  (delete-char 1))))
    (if (and recursive
diff --git a/lisp/textmodes/sgml-mode.el b/lisp/textmodes/sgml-mode.el
index 2ffe9c1..6a14b52 100644
--- a/lisp/textmodes/sgml-mode.el
+++ b/lisp/textmodes/sgml-mode.el
@@ -759,9 +759,10 @@ If QUIET, do not print a message when there are no 
attributes for TAG."
  	    (insert ?\s)
  	    (insert (funcall skeleton-transformation-function
  			     (setq attribute
-				   (skeleton-read '(completing-read
-						    "Attribute: "
-						    alist)))))
+				   (skeleton-read (lambda ()
+                                                    (completing-read
+                                                     "Attribute: "
+                                                     alist))))))
  	    (if (string= "" attribute)
  		(setq i 0)
  	      (sgml-value (assoc (downcase attribute) alist))
@@ -1177,13 +1178,16 @@ See `sgml-tag-alist' for info about attribute 
rules."
      (if (and (eq (car alist) t) (not sgml-xml-mode))
  	(when (cdr alist)
  	  (insert "=\"")
-	  (setq alist (skeleton-read '(completing-read "Value: " (cdr alist))))
+	  (setq alist (skeleton-read (lambda ()
+                                       (completing-read
+                                        "Value: " (cdr alist)))))
  	  (if (string< "" alist)
  	      (insert alist ?\")
  	    (delete-char -2)))
        (insert "=\"")
        (if (cdr alist)
-          (insert (skeleton-read '(completing-read "Value: " alist)))
+          (insert (skeleton-read (lambda ()
+                                   (completing-read "Value: " alist))))
          (when (null alist)
            (insert (skeleton-read '(read-string "Value: ")))))
        (insert ?\"))))
-- 
2.4.5