Error handling in org-make-link-string

Error handling in org-make-link-string

[Bob Newell]

Aloha,

I've got a subsystem for capturing snippets of information (I mentioned
it here, scraps.el, quite some while back). Some information is captured
from w3m or eww browser buffers.

To do this I use org-w3m-copy-for-org-mode or
org-eww-copy-for-org-mode. This is nice in that links are converted to
org-mode links, using org-make-link-string.

The problem? When org-make-link-string encounters an empty link (it
doesn't happen often but it does happen), it uses the 'error' function
to say that the link is empty. This means that the entire call to
org-xxx-copy-for-org-mode is aborted, and consequently nothing is
captured.

Should this be the desired behavior?

It doesn't quite work for me, but I'm not sure about other uses, side
effects, etc. Someone more familiar with org-mode code would have to
decide. My workaround, since I don't want to modify org.el directly and
have to maintain the mod, is this fairly primitive idea:

    (defun rjn-around-omls (orig-fun link &rest args)
      (if (org-string-nw-p link)
	  (apply orig-fun link args)
	  nil))
    (advice-add 'org-make-link-string :around #'rjn-around-omls)

This works fine for me in that an empty link is simply returned as nil
and ignored. (I suppose I could add an error message.)

Any thoughts on (a) is the 'error' return the right thing, and (b) this
workaround?

Mahalo,

-- 
Bob Newell
Honolulu, Hawai`i
* Via Gnus/BBDB/Org/Emacs/Linux *

Re: Error handling in org-make-link-string

[Nicolas Goaziou]

Hello,

Bob Newell <bobnewell@bobnewell.net> writes:

> The problem? When org-make-link-string encounters an empty link (it
> doesn't happen often but it does happen), it uses the 'error' function
> to say that the link is empty. This means that the entire call to
> org-xxx-copy-for-org-mode is aborted, and consequently nothing is
> captured.
>
> Should this be the desired behavior?

Your question is twofold. 

OTOH, it seems sane to expect `org-make-link-string' to throw an error
if you try to apply it on garbage. OTOH, I agree it is not desirable to
throw away all captured information because of a bad link.

I think the problem lies in the logic of `org-eww-copy-for-org-mode' and
`org-w3m-copy-for-org-mode', which should handle better errors from
`org-make-link-string'.

For example,

   (if (stringp link-location)
       ;; hint: link-location is different for form-elements.
       (org-make-link-string link-location link-title)
    link-title)

could be replaced with

  (if (org-string-nw-p link-location)
      ...)

or even

  (or (ignore-errors (org-make-link-string ...))
      link-title)

WDYT?

Regards,

-- 
Nicolas Goaziou

Re: Error handling in org-make-link-string

[Bob Newell]

Aloha,

Either of your suggested solutions would work, of course, and limit
effects to org-xxx-copy-for-org-mode. I didn't go that way because I
didn't want to have to continually modify the core product on my own
:)

The idea of

(if (org-string-nw-p link-location

etc. may be best because we can have a guaranteed nil on a bad link,
rather than ignore-errors which (I think?) may have a different
return. I didn't put an error message in my 'advice' workaround but it
would be a good idea.

Regards,


Bob


On Sat, Apr 14, 2018 at 3:17 AM, Nicolas Goaziou <mail@nicolasgoaziou.fr> wrote:
> Hello,
>
> Bob Newell <bobnewell@bobnewell.net> writes:
>
>> The problem? When org-make-link-string encounters an empty link (it
>> doesn't happen often but it does happen), it uses the 'error' function
>> to say that the link is empty. This means that the entire call to
>> org-xxx-copy-for-org-mode is aborted, and consequently nothing is
>> captured.
>>
>> Should this be the desired behavior?
>
> Your question is twofold.
>
> OTOH, it seems sane to expect `org-make-link-string' to throw an error
> if you try to apply it on garbage. OTOH, I agree it is not desirable to
> throw away all captured information because of a bad link.
>
> I think the problem lies in the logic of `org-eww-copy-for-org-mode' and
> `org-w3m-copy-for-org-mode', which should handle better errors from
> `org-make-link-string'.
>
> For example,
>
>    (if (stringp link-location)
>        ;; hint: link-location is different for form-elements.
>        (org-make-link-string link-location link-title)
>     link-title)
>
> could be replaced with
>
>   (if (org-string-nw-p link-location)
>       ...)
>
> or even
>
>   (or (ignore-errors (org-make-link-string ...))
>       link-title)
>
> WDYT?
>
> Regards,
>
> --
> Nicolas Goaziou



-- 
Bob Newell
Honolulu, Hawai`i

Sent via Linux Mint 17.

Re: Error handling in org-make-link-string

[Nicolas Goaziou]

Hello,

Bob Newell <bobnewell@bobnewell.net> writes:

> Aloha,
>
> Either of your suggested solutions would work, of course, and limit
> effects to org-xxx-copy-for-org-mode. I didn't go that way because I
> didn't want to have to continually modify the core product on my own
> :)
>
> The idea of
>
> (if (org-string-nw-p link-location
>
> etc. may be best because we can have a guaranteed nil on a bad link,
> rather than ignore-errors which (I think?) may have a different
> return. I didn't put an error message in my 'advice' workaround but it
> would be a good idea.

Done. Thank you.

Regards,

-- 
Nicolas Goaziou