sgml-mode skip tag forward/back bug fix

sgml-mode skip tag forward/back bug fix

[Mallory, Rich]

Your bug report will be posted to the bug-gnu-emacs@gnu.org mailing list,
and to the gnu.emacs.bug news group.

In GNU Emacs 21.2.1 (i386-msvc-nt5.0.2195) of 2002-03-19 on buffy
configured using `configure --with-msvc (12.00)'
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: ENU
  locale-coding-system: iso-latin-1
  default-enable-multibyte-characters: t

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

In editing an XML file in sgml-mode, the commands sgml-skip-tag-forward and
sgml-skip-tag-backward failed as follows.  When an outer element contained an
inner element and the inner element's tag name began with the outer element's
tag name but was longer, these commands did not skip the whole outer element,
from start tag to end tag (or back), but only part of it.

For example, in the XML --
  <foo>
    <whatever .../>
    <fooBar note="Tag name begins with 'foo', the outer tag name." />
    <something .../>
  </foo>
 -- with the cursor before <foo>, sgml-skip-tag-forward would only skip to the 
end of tag <foo>, not to the end of tag </foo>, and 
 -- with the the cursor after </foo>, sgml-skip-tag-backward would only skip to 
the beginning of <fooBar .../>, not to the beginning of <foo>.

Proposed fix: The changelog and proposed changes to the code are shown below.
The added elements of the regexps cause the search code to look for the end of
the tag name, not just its beginning.  The new code seems to work correctly.
However, I am not sure that the added regexp elements are are sufficiently
general to cover all cases.

Change log
2002-04-26  Rich Mallory  <mallory@ausinfo.com>
	* lisp/textmodes/sgml-mode.el (sgml-skip-tag-backward, sgml-skip-tag-forward):
	Fix bug where an outer element containing an inner element whose name
	began with the outer name (e.g., <foo> ... <fooBar ... /> ... </foo>)
	was not properly skipped.

Diffs between old sgml-mode.el (<) and new (>)
In sgml-skip-tag-backward --
656c656
< 	      (re (concat "</?" (regexp-quote (match-string 1)))))
---
> 	      (re (concat "</?" (regexp-quote (match-string 1)) "[/ \n\t>]")))

In sgml-skip-tag-forward --
676c676
< 	      (re (concat "</?" (regexp-quote (match-string 1))))
---
> 	      (re (concat "</?" (regexp-quote (match-string 1)) "[/ \n\t>]"))

(I haven't actually modified sgml-mode.el but put the changes in another file.
The diffs above show what has been changed.)

-- Rich Mallory

Re: sgml-mode skip tag forward/back bug fix

[Stefan Monnier]

>>>>> "Mallory," == Mallory, Rich <Rich.Mallory@ausinfo.com> writes:
> In editing an XML file in sgml-mode, the commands sgml-skip-tag-forward and
> sgml-skip-tag-backward failed as follows.  When an outer element contained an
> inner element and the inner element's tag name began with the outer element's
> tag name but was longer, these commands did not skip the whole outer element,
> from start tag to end tag (or back), but only part of it.

Note that the sgml-mode.el has been changed in the CVS repository to better
support XML, so you might want to try it out.
See http://savannah.gnu.org/projects/emacs.

> 2002-04-26  Rich Mallory  <mallory@ausinfo.com>
> 	* lisp/textmodes/sgml-mode.el (sgml-skip-tag-backward, sgml-skip-tag-forward):
> 	Fix bug where an outer element containing an inner element whose name
> 	began with the outer name (e.g., <foo> ... <fooBar ... /> ... </foo>)
> 	was not properly skipped.

Thank you.  I'll see if it has been fixed already.
BTW, it is generally preferable to use `diff -u' or `diff -c' when sending
diffs (and not only for Emacs maintainers).


    Stefan