Re: org-export: how to copy the parsed tree?

[Nicolas Goaziou <n.goaziou@gmail.com>]

Vitalie Spinu <spinuvit@gmail.com> writes:

> Thanks Nocolas. I need to copy only a subtree associated with a
> headline. In a nutshell I need to "flatten" the tree of headlines for
> the csv type exporter. That is, I need to replicate the parent headlines
> across the children. For example
>    
>    * H1
>      bla bla
>    ** HA
>       some text
>    ** HB
>       some other text
>    
> would translate into 
>    
>    * H1
>      bla bla
>    ** HA
>       some text
>    * H1
>      bla bla
>    ** HB
>       some other text
>
> I played with org-element-extract-element, org-element-set-contents and
> org-element-insert-before but failed a big deal.

In this case, I think I would build the tree, since data is duplicated
(e.g. "* H1"), not moved.

> Main problem seems to be the lack of uniform interface to handle parents
> in connection to secondary elements (which I don't understand at this
> point).

There is no such thing as "secondary elements". I think you mean
"secondary strings". This is some parsed data that doesn't belong to the
main hierarchy in the tree.

I don't think any interface problem for :parent property. You simply use
`org-element-property' and `org-element-put-property'.

> Is headline a secondary element?

No. A headline is a full-fledged element. But, besides its contents, it
contains additional data (its title) which is Org syntax and therefore
qualifies as a secondary string.

> The :parent seems to be stored in 2 places for the headline, in the
> headline itself and in the :title.

You are wrong. Headline's parent is stored only in the :parent property
of the headline. You get it with:

  (org-element-property :parent headline)

Within `:title', `:parent' property refers to the parent of the objects
contained in :title, which is the headline itself:

  (eq (org-element-property :parent
                            ;; The first object in the :title property.
                            (car (org-element-property :title headline)))
      headline)  => t

There is only one parent per object/element/string.

> Most of the org code uses org-element-put-property and
> org-element-property to access the parent but some code like
> org-element-extract-element uses :parent from :title.

`org-element-extract-element' checks if the element/object you're
removing belong to a secondary string or to the contents of the current
element.

Moreover, this function removes the :parent property, so you shouldn't
bother about where it came from.

> This makes it difficult to program as there are no explicit
> getter/setter for the parent.

See above.

> BTW, is there a way to pretty print the org tree? I think that's the
> main barrier for me in understanding how it all works.

Use `pp' and set both `print-level' and `print-circle' accordingly.


Regards,

-- 
Nicolas Goaziou