21.5.28: replace-regexp-in-string with SUBEXP is broken

[David Kastrup]

"Stephen J. Turnbull" <stephen at xemacs.org> writes:

> Ville Skyttä writes:
>
>  > replace-regexp-in-string with SUBEXP in 21.5.28 is broken; for example the 
>  > example given in the docstring fails.
>
> The whole Emacs matching API really sucks. :-(
>
>  > What should happen according to the example:
>  > 
>  >    (replace-regexp-in-string "\\(foo\\).*\\'" "bar" " foo foo" nil nil 1)
>  >    " bar foo"

Does so in Emacs.

> but this is only used in the rare case that rep is a function.  I
> actually don't think this makes sense.  Consider this example:
>
 (defun rep (s)
          (if (string= s "foo") "bar" s))
   (replace-regexp-in-string "\\(foo\\).*\\'" 'rep " foo foo" nil nil 1)

> I would expect that to result in " bar foo", but as written here (and
> as specified in the docstring) that results in " foo foo" because
> (match-string 0 str) is " foo foo" here.  We should look at GNU's
> implementatation to see what they do.

" foo foo foo".  It is possible that this may be a bug, but the DOC
string of replace-regexp-in-string makes my eyes glaze over, anyway.
If you have a good definite idea about what would be the correct
behavior and why, and you care about keeping code divergence to a
minimum, you might make and report a test case.

> For another thing, I discovered either `match-end' or `\'' appears
> broken on strings:
>
> (let ((s " foo foo"))
>   ;; my-rris is `replace-regexp-in-string' without saving match data
>   (list (my-rris "\\(foo\\).*\\'" "bar" s nil nil 1)
> 	(match-string 0 s)
> 	(match-string 1 s)
> 	(length s)
> 	(match-beginning 0)
> 	(match-end 0)
> 	(match-beginning 1)
> 	(match-end 1)))
> => (" bar" " foo fo" " fo" 8 0 7 0 3)
>
> The first element is the bug that Ville reported but the rest is,
> well, disturbing.  Anybody know what's going on here?

Emacs: (" bar foo" " foo fo" " fo" 8 0 7 0 3)

I am not sure about the relevance of "rris without match-data" though.

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum