Re: [PATCH] Omit file description when :file-desc has nil value

[Matt Huszagh]

Kyle Meyer <kyle@kyleam.com> writes:

> But it's not a direct comparison against that use case and the use case
> you want to support.  The potential breakage of existing documents is a
> big factor to go against.

Yep, I agree. I think my phrasing could have just been better. I meant
to include the breakage as a factor against.

> Unfortunately, such a kludge is how I'd suggest to move forward.
> Perhaps an empty string, or perhaps any value (e.g., ":file-desc []")
> that org-babel-read won't treat as a string or nil (the two cases that
> mean something right now).  The rough patch below is an example of the
> latter.

I like this solution better than mine. I guess it's still a bit of a
hack, but it doesn't seem to be one that could break a use case, whereas
the empty string could conceivably be intended, though I'm still not
sure why.

> I'm not sure I get this.  What's next down the road in this scenario?
> With something like the above kludge, haven't we exhausted the cases for
> :file-desc?

Yes I think you're right. I was referring to my solution of an empty
string, which I didn't see a personal use for, but felt it might be a
valid use case for someone else. I really can't think of any reason the
empty vector would otherwise be valid.

> diff --git a/lisp/ob-core.el b/lisp/ob-core.el
> index 7300f239e..4483585a1 100644
> --- a/lisp/ob-core.el
> +++ b/lisp/ob-core.el
> @@ -646,6 +646,13 @@ (defun org-babel--expand-body (info)
>        (replace-regexp-in-string
>         (org-src-coderef-regexp coderef) "" expand nil nil 1))))
>  
> +(defun org-babel--file-desc (params result)
> +  (pcase (assq :file-desc params)
> +    (`nil nil)
> +    (`(:file-desc) result)
> +    (`(:file-desc . ,(and (pred stringp) val)) val)
> +    (_ nil)))
> +
>  ;;;###autoload
>  (defun org-babel-execute-src-block (&optional arg info params)
>    "Execute the current source code block.
> @@ -749,8 +756,7 @@ (defun org-babel-execute-src-block (&optional arg info 
> params)
>                   (let ((*this* (if (not file) result
>                                   (org-babel-result-to-file
>                                    file
> -                                  (let ((desc (assq :file-desc params)))
> -                                    (and desc (or (cdr desc) result)))))))
> +                                  (org-babel--file-desc params result)))))
>                     (setq result (org-babel-ref-resolve post))
>                     (when file
>                       (setq result-params (remove "file" result-params))))))
> @@ -2257,9 +2263,8 @@ (defun org-babel-insert-result (result &optional 
> result-params info hash lang)
>        (setq result (org-no-properties result))
>        (when (member "file" result-params)
>          (setq result (org-babel-result-to-file
> -                      result (when (assq :file-desc (nth 2 info))
> -                               (or (cdr (assq :file-desc (nth 2 info)))
> -                                   result))))))
> +                      result
> +                      (org-babel--file-desc (nth 2 info) result)))))
>       ((listp result))
>       (t (setq result (format "%S" result))))
>    (if (and result-params (member "silent" result-params))
> diff --git a/testing/lisp/test-ob.el b/testing/lisp/test-ob.el
> index 648e9c115..e7a292de3 100644
> --- a/testing/lisp/test-ob.el
> +++ b/testing/lisp/test-ob.el
> @@ -1084,7 +1084,16 @@ (ert-deftest test-ob/file-desc-header-argument ()
>      (org-babel-execute-src-block)
>      (goto-char (point-min))
>      (should (search-forward "[[file:foo][bar]]" nil t))
> -    (should (search-forward "[[file:foo][foo]]" nil t))))
> +    (should (search-forward "[[file:foo][foo]]" nil t)))
> +  (should (string-match-p
> +        (regexp-quote "[[file:foo]]")
> +        (org-test-with-temp-text "
> +#+begin_src emacs-lisp :results file :file-desc []
> +  \"foo\"
> +#+end_src"
> +          (org-babel-next-src-block)
> +          (org-babel-execute-src-block)
> +          (buffer-substring-no-properties (point-min) (point-max))))))
>  
>  (ert-deftest test-ob/result-file-link-type-header-argument ()
>    "Ensure that the result is a link to a file.

This patch looks good. I've tested it and it works well for me. Thanks
for coming up with a good solution! I think the one thing still missing
is some documentation in the info manual. Something along the lines of

     The ‘file-desc’ header argument defines the description (see *note
     Link Format::) for the link.  If ‘file-desc’ has no value, Org uses
     the generated file name for both the “link” and “description” parts
     of the link. If you want to omit the description (i.e., [[link]]),
     you can either omit the ‘file-desc’ header argument or provide it
     with an empty vector (i.e., :file-desc []).

Feel free to add this (or something else) to your patch. Or, if you'd
prefer that I created a patch for it, let me know.

Matt