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

[Kyle Meyer]

Matt Huszagh writes:

> Subject: [PATCH] list/ob-core.el: Allow passing empty vector to :file-desc to
>  omit description

s/list/lisp/

> diff --git a/doc/org-manual.org b/doc/org-manual.org
> index e7d25b90e..a790f3225 100644
> --- a/doc/org-manual.org
> +++ b/doc/org-manual.org
> @@ -17482,10 +17482,12 @@ default behavior is to automatically determine the 
> result type.
>    #+end_example
>  
>    #+cindex: @samp{file-desc}, header argument
> -  The =file-desc= header argument defines the description (see
> -  [[*Link Format]]) for the link.  If =file-desc= is present but has no 
> value,
> +  The =file-desc= header argument defines the description (see [[*Link
> +  Format]]) for the link.  If =file-desc= is present but has no value,
>    the =file= value is used as the link description.  When this
> -  argument is not present, the description is omitted.
> +  argument is not present, the description is omitted.  If you want to
> +  provide the =file-disc= argument but omit the description, you can

s/file-disc/file-desc/

> +  provide it with an empty vector (i.e., :file-desc []).

> diff --git a/etc/ORG-NEWS b/etc/ORG-NEWS
> index 5dc68cba4..19f6af288 100644
> --- a/etc/ORG-NEWS
> +++ b/etc/ORG-NEWS
> @@ -24,8 +24,19 @@ Earlier, IDs generated using =ts= method had a hard-coded 
> format (i.e. =20200923
>  The new option allows user to customise the format.
>  Defaults are unchanged.
>  
> +*** New argument for ~file-desc~ babel header
[...]
>  ** New features
> -*** =ob-python= improvements to =:return= header argument 
> +*** =ob-python= improvements to =:return= header argument

This space change is touching unrelated code.

>  The =:return= header argument in =ob-python= now works for session
>  blocks as well as non-session blocks.  Also, it now works with the
> diff --git a/lisp/ob-core.el b/lisp/ob-core.el
> index 7300f239e..075e3f928 100644
> --- a/lisp/ob-core.el
> +++ b/lisp/ob-core.el
> @@ -646,6 +646,14 @@ a list with the following pattern:
>        (replace-regexp-in-string
>         (org-src-coderef-regexp coderef) "" expand nil nil 1))))
>  
> +(defun org-babel--file-desc (params result)
> +  "Retrieve file description."
> +  (pcase (assq :file-desc params)
> +    (`nil nil)

All right, so this is the no header case...

> +    (`(:file-desc) result)

...this is for when org-babel-read maps the value to nil...

> +    (`(:file-desc . ,(and (pred stringp) val)) val)

...and when org-babel-read maps it to a string...

> +    (`(:file-desc . []) nil)))

...and this the explicit vector.

Operationally any value that org-babel-read doesn't map to nil or a
string leads to nil.  The pcase expression then could be reduced to

    (pcase (assq :file-desc params)
      (`(:file-desc) result)
      (`(:file-desc . ,(and (pred stringp) val)) val))

However, I'm okay with it as is, particularly the [] arm, because I
think it helps readability wise to explicitly spell out the documented
case.

So, with the typo/spurious space change clean-ups, this looks good to
me.  IIRC from a previous thread, you haven't yet completed the
copyright paperwork.  Is that the case?

Thanks.