path: root/doc/todo/matching_different_kinds_of_links.mdwn

[[!tag wishlist]]
As noted in [[todo/tag_pagespec_function]], there is a "misbehavior" of a tagged() pagespec: it matches even pages which have plain links to the tag page.
And in general, it would be quite useful to be able to distinguish different kinds of links: one more kind, in addition to "tag", is "bug dependency" noted in [[todo/structured_page_data#another_kind_of_links]] and [[todo/tracking_bugs_with_dependencies#another_kind_of_links]].
It could distinguish the links by the rel= attribute. ([[Tags already receive a special rel-class|todo/rel_attribute_for_links]].) This means there is a general need for a syntax to specify user-defined rel-classes on wikilink (then bug deps would simply use their special rel-class, either directly, or through a special directive like \[[!depends ]]), and to refer to them in pagespecs (in forward and backward direction).
Besides pagespecs, the rel= attribute could be used for styles. --Ivan Z.

FWIW, the add_link function introduced in a recent
release adds an abstraction that could be used to get
part of the way there to storing data about different types of
links. That function could easily be extended to take an optional
third parameter specifying the link type.
Then there's the question of how to store and access the data. %links
does not offer a good way to add additional information about links.
Now, we could toss %links entirely and switch to an accessor function,
but let's think about not doing that..
The data that seems to be needed is basically a deep hash, so
one could check $linktype{$page}{tag}{$link} to see if
the page contains a link of the given type. (Note that pages could
contain links that were duplicates except for their types.)
There would be some data duplication, unfortuantly, but if %linktype
is not populated for regular wikilinks, it would at least be limited to
tags and other unusual link types, so not too bad.
%linktype could be stored in %pagestate.. if so
the actual use might look like $pagestate{$page}{linktype}{tag}{$link}.
That could be implemented by the tag plugin right now
with no core changes. (BTW, then I originally wrote tag, pagestate
was not available, which is why I didn't make it differentiate from
normal links.) Might be better to go ahead and add the variable to
core though. --[[Joey]]



I've implemented this with the data structure you suggested, except that
I called it %typedlinks instead of %linktype (it seemed to make more
sense that way). I also ported tag to it, and added a tagged_is_strict
config option. See below! --[[smcv]]


I saw somewhere else here some suggestions for the wiki-syntax for specifying the relation name of a link. One more suggestion---the syntax used in Semantic MediaWiki, like this:

So a part of the effect of [[\[[!taglink TAG\]\]|plugins/tag]] could be represented as something like \[[tag::TAG]] or (more understandable relation name in what concerns the direction) \[[tagged::TAG]].
I don't have any opinion on this syntax (whether it's good or not)...--Ivan Z.



[[!template id=gitbranch author="[[Simon_McVittie|smcv]]" branch=smcv/link-types]]
[[!tag patch]]


Documentation for smcv's branch
added to [[ikiwiki/pagespec]]

"typedlink(type glob)" - matches pages that link to a given page (or glob)
with a given link type. Plugins can create links with a specific type:
for instance, the tag plugin creates links of type tag.

added to [[plugins/tag]]
If the tagged_is_strict config option is set, tagged() will only match
tags explicitly set with [[ikiwiki/directive/tag]] or
[[ikiwiki/directive/taglink]]; if not (the default), it will also match
any other [[WikiLinks|ikiwiki/WikiLink]] to the tag page.
added to [[plugins/write]]
%typedlinks
The %typedlinks hash records links of specific types. Do not modify this
hash directly; call add_link(). The keys are page names, and the values
are hash references. In each page's hash reference, the keys are link types
defined by plugins, and the values are hash references with link targets
as keys, and 1 as a dummy value, something like this:
$typedlinks{"foo"} = {
	tag => { short_word => 1, metasyntactic_variable => 1 },
	next_page => { bar => 1 },
};

Ordinary [[WikiLinks|ikiwiki/WikiLink]] appear in %links, but not in
%typedlinks.
add_link($$;$)
This adds a link to %links, ensuring that duplicate links are not
added. Pass it the page that contains the link, and the link text.
An optional third parameter sets the link type (undef produces an ordinary
[[ikiwiki/WikiLink]]).