Re: greedy substitution in org-open-file

[Maxim Nikulin]

On 13/02/2021 11:38, Kyle Meyer wrote:
> All right, here's
> a format-spec-inspired fix.  At the very least it needs doc updates and
> a comment or two.

Thank you. I am hardly familiar with elisp so it would be difficult for 
me to express the same. My comments are mostly a matter of taste.

Sorry, I have not tried to run the code yet.

> diff --git a/lisp/org.el b/lisp/org.el
> index 5b1443c4e..e8f60fd83 100644
> --- a/lisp/org.el
> +++ b/lisp/org.el
> @@ -8644,6 +8644,23 @@ (defun org--file-apps-regexp-alist (list &optional 
> add-auto-mode)
>      (when add-auto-mode
>        (mapcar (lambda (x) (cons (car x) 'emacs)) auto-mode-alist))))
>   
> +(defun org--open-file-format-spec (format specification)
> +  (with-temp-buffer
> +    (insert format)
> +    (goto-char (point-min))
> +    (while (search-forward "%" nil t)
> +      (cond ((eq (char-after) ?%)
> +             (delete-char 1))
> +            ((looking-at "[s0-9]")

Personally I do not see a reason to limit substitutions just to just 
"%s". I would consider "[a-zA-Z0-9]".

> +             (replace-match
> +              (or (cdr (assoc (match-string 0) specification))
> +                  (error "Invalid format string"))

I think, substitution character in the error message could be useful 
during debugging, something like (format "Invalid format character %%%s" 
(match-string 0)).

> +              'fixed-case 'literal)
> +             (delete-region (1- (match-beginning 0)) (match-beginning 0)))
> +            (t
> +             (error "Invalid format string"))))
> +    (buffer-string)))
> +
>   ;;;###autoload
>   (defun org-open-file (path &optional in-emacs line search)
>     "Open the file at PATH.
> @@ -8745,24 +8762,20 @@ (defun org-open-file (path &optional in-emacs line 
> search)
>         ;; Remove quotes around the file name - we'll use shell-quote-argument.
>         (while (string-match "['\"]%s['\"]" cmd)
>         (setq cmd (replace-match "%s" t t cmd)))
> -      (setq cmd (replace-regexp-in-string
> -                "%s"
> -                (shell-quote-argument (convert-standard-filename file))
> -                cmd
> -                nil t))
> -
> -      ;; Replace "%1", "%2" etc. in command with group matches from regex
> -      (save-match-data
> -       (let ((match-index 1)
> -             (number-of-groups (- (/ (length link-match-data) 2) 1)))
> -         (set-match-data link-match-data)
> -         (while (<= match-index number-of-groups)
> -           (let ((regex (concat "%" (number-to-string match-index)))
> -                 (replace-with (match-string match-index dlink)))
> -             (while (string-match regex cmd)
> -               (setq cmd (replace-match replace-with t t cmd))))
> -           (setq match-index (+ match-index 1)))))
> -
> +      (setq cmd
> +            (org--open-file-format-spec
> +             cmd
> +             (cons
> +              (cons "s" (shell-quote-argument
> +                         (convert-standard-filename file)))
> +              (let ((ngroups (- (/ (length link-match-data) 2) 1)))
> +                (and (> ngroups 0)
> +                     (progn
> +                       (set-match-data link-match-data)
> +                       (mapcar (lambda (n)
> +                                 (cons (number-to-string n)
> +                                       (match-string-no-properties n dlink)))

Should not be numbered substitutions passed through shell-quote-argument 
as well? Besides just page numbers the link could be named internal 
anchor where more characters are allowed. It is the reason why in 
general I prefer bare exec to shell commands.

I am unsure concerning optional matches as

    "\\(?:\\.pdf\\)\\(?:::\\([0-9]+\\)\\)?\\'"

Maybe they should not be used at all in favor of separate entries with 
and without page number. Maybe nil should coalesce to empty string "". 
Certainly I am against "nil" string for a missed group. By the way, in 
the original format-spec, cdr is applied after the check whether assoc 
value is nil.

> +                               (number-sequence 1 ngroups))))))))
>         (save-window-excursion
>         (message "Running %s...done" cmd)
>         (start-process-shell-command cmd nil cmd)