X-Git-Url: http://git.vanrenterghem.biz/git.ikiwiki.info.git/blobdiff_plain/8c2d221ca93ed6fbe8f093408c4e2cea835e5b4c..77598dfa9fccb668345198ea169cf7cf00b9845e:/doc/todo/dependency_types.mdwn

diff --git a/doc/todo/dependency_types.mdwn b/doc/todo/dependency_types.mdwn
index 6d722aab9..19294bba0 100644
--- a/doc/todo/dependency_types.mdwn
+++ b/doc/todo/dependency_types.mdwn
@@ -10,12 +10,12 @@ whenever a matching dependency is added, removed, or *modified*. But a
 great many things don't care about the modification case, and often cause
 unnecessary page rebuilds:
 
-* meta only cares if the pages are added or removed. Content change does
+* map only cares if the pages are added or removed. Content change does
   not matter (unless show=title is used).
-* brokenlinks, orphans, pagecount, ditto
+* brokenlinks, orphans, pagecount, ditto (generally)
 * inline in archive mode cares about page title, author changing, but
   not content. (Ditto for meta with show=title.)
-* Causes extra work when solving the [[bug/transitive_dependencies]]
+* Causes extra work when solving the [[bugs/transitive_dependencies]]
   problem.
 
 ### two types of dependencies needed for [[tracking_bugs_with_dependencies]]
@@ -105,14 +105,11 @@ unnecessary page rebuilds:
 
 I propose the following. --[[Joey]] 
 
-* Add a second type of dependency, call it an "contentless dependency".
+* Add a second type of dependency, call it an "presence dependency".
 * `add_depends` defaults to adding a regular ("full") dependency, as
   before. (So nothing breaks.)
-* `add_depends($page, $spec, content => 0)` adds an contentless dependency.
-* Contentless dependencies are stored in `%depends_contentless` and
-  `%depends_contentless_simple`, which are stored in the index similarly
-  to the existing hashes.
-* `refresh` only looks at added/removed pages when resolving contentless
+* `add_depends($page, $spec, presence => 0)` adds an presence dependency.
+* `refresh` only looks at added/removed pages when resolving presence
   dependencies.
 
 This seems straightforwardly doable. I'd like [[Will]]'s feedback on it, if
@@ -121,5 +118,58 @@ to the two types he talks about above, but I hope are close enough that
 they can be used.
 
 This doesn't deal with the stuff that only depend on the metadata of a
-page, as collected in the scan pass, changing. But it does leave a window
+page, as collected in the scan pass, changing.  But it does leave a window
 open for adding such a dependency type later.
+
+----
+
+I implemented the above in a branch.
+[[!template id=gitbranch branch=origin/dependency-types author="[[joey]]"]]
+
+Then I found some problems:
+
+* Something simple like pagecount, that seems like it could use a
+  presence dependency, can have a pagespec that uses metadata, like
+  `author()` or `copyright()`.
+* pagestats, orphans and brokenlinks cannot use presence dependencies
+  because they need to update when links change.
+
+Now I'm thinking about having a special dependency look at page
+metadata, and fire if the metadata changes. And it seems links should
+either be included in that, or there should be a way to make a dependency
+that fires when a page's links change. (And what about backlinks?)
+
+It's easy to see when a page's links change, since there is `%oldlinks`.
+To see when metadata is changed is harder, since it's stored in the
+pagestate by the meta plugin. Also, there are many different types of
+metadata, that would need to be matched with the pagespecs somehow.
+
+Quick alternative: Make add_depends look at the pagespec. Ie, if it
+is a simple page name, or a glob, we know a presence dependency
+can be valid. If's more complex, convert the dependency from
+presence to full.
+
+There is a lot to dislike about this method. Its parsing of the pagespec,
+as currently implemented, does not let plugins add new types of pagespecs
+that only care about presence. Its pagespec parsing is also subject to
+false negatives (though these should be somewhat rare, and no false
+positives). Still, it does work, and it makes things like simple maps and
+pagecounts much more efficient.
+
+---- 
+
+Link dependencies:
+
+* `add_depends($page, $spec, links => 1, presence => 1)`
+  adds a links + presence dependency.
+* Use backlinks change code to detect changes to link dependencies too.
+* So, brokenlinks can fire whenever any links in any of the
+  pages it's tracking change, or when pages are added or
+  removed.
+* To determine if a pagespec is valid to be used with a links dependency,
+  use the same set that are valid for presence dependencies. But also
+  allow `backlinks()` to be used in it, since that matches pages
+  that the page links to, which is just what link dependencies are
+  triggered on.
+
+[[done]]