Re: [O] How to change a link?

[Thorsten Jolitz]

Marcin Borkowski <address@hidden> writes:

> On 2014-10-15, at 23:52, Nicolas Goaziou wrote:
>
>> Marcin Borkowski <address@hidden> writes:
>>
>>> I have one more question.  What I'm about to do is (basically) put
>>> "file:some-file-name::" in front of the link, without changing the
>>> description.  I could use `org-element-put-property' and (AFAIU)
>>> org-element-link-interpreter to put it into the buffer (and probably
>>> delete the old one).  It would be much easier (and maybe faster) just to
>>> go to the point in the buffer where the link starts, go `(forward-char
>>> 2)' (past the brackets) and `(insert (concat "file" name "::"))'.
>>>
>>> But, is it safe?  Wouldn't it break something?  And is it considered a
>>> good practice?
>>
>> There are caveats.
>>
>> For example, as soon as you alter the buffer, your AST becomes invalid
>> (buffer positions are all wrong after the insertion). If you want to
>> process all the links from the same AST, you can, for example, maintain
>> a counter for characters inserted so far that will fix buffer positions,
>> or first get all internal links with `org-element-map', then process
>> them in reverse order so buffer modifications do not invalidate them.
>
> OK, so what is the canonical way of doing this?  I don't want to use
> org-dp, since it is another dependency.

It is a problem to add dependencies to libraries the user must install
himself, and at the same time its a pity that there is so much
duplication instead of reuse ...

However, here is a org-dp solution, use 't' instead of 'prepend to
replace the links, and whatever you want instead of "file+emacs" as
replacement. Of course one could easily re-search and replace "[[file:"
in this simple case, but this uses the parser and allows doing more
complex stuff in a clean way too:

,----
| * ORG SCRATCH
| 
| ** Level 2
| 
| [[file+emacs:~/junk/org/minimal.org][min.org]]
| 
| [[file:~/junk/org/minimal.org][min.org]]
| 
| *** Level 3
| 
| [[file+emacs:~/junk/org/trash-me.org][trash.org]]
| 
| [[file:~/junk/org/trash-me.org][trash.org]]
| 
| 
| #+BEGIN_SRC emacs-lisp :results none
|   (require 'org-dp)
|   (org-dp-map
|    '(org-dp-rewire
|      'paragraph 
|      (lambda (cont elem)
|        (let* ((link (car cont))
|               (raw-val (org-element-property :raw-link link))
|               (new-val (mapconcat 'identity
|                                   (cons "file+emacs"
|                                         (cdr
|                                          (split-string
|                                           raw-val ":" t)))
|                                   ":")))
|          (org-element-put-property link :raw-link new-val)))
|      'prepend)
|    org-link-re-with-space t)
| #+END_SRC
`----

-- 
cheers,
Thorsten