X-Git-Url: http://git.vanrenterghem.biz/git.ikiwiki.info.git/blobdiff_plain/6bc787e14c114cd93d5c35ffeb5ba57529f66eef..65959c852875f9a3fd7e90d2fa777a3333ba7038:/doc/bugs/conditional_preprocess_during_scan.mdwn

diff --git a/doc/bugs/conditional_preprocess_during_scan.mdwn b/doc/bugs/conditional_preprocess_during_scan.mdwn
index 896998bf8..254ebac22 100644
--- a/doc/bugs/conditional_preprocess_during_scan.mdwn
+++ b/doc/bugs/conditional_preprocess_during_scan.mdwn
@@ -8,3 +8,30 @@ I've written a simple [[patch]] to fix the issue, currently hosted on the
 scanif branch of my repository. The patch also passes the preview option
 back to the Ikiwiki::preprocess call, making sure that whatever is being
 reprocessed is done so in the same conditions as the original call.
+
+> One problem with this is that it has the same dependency-ordering problems
+> as inline-based or pagespec-based trails with my [[plugins/contrib/trail]]
+> plugin: `if` takes a pagespec, but pagespecs aren't guaranteed to match
+> correctly until everything has been scanned (for instance, `link()` might
+> give the wrong results because a page that added or deleted a link hasn't
+> been scanned yet). If you have a clever idea for how to fix this, I'd love
+> to hear it - being able to specify a [[plugins/contrib/trail]] in terms
+> of a sorted pagespec would be useful. --[[smcv]]
+
+>> I have a solution to the dependency-ordering problem in a different
+>> branch of my repository, with a post_scan hook mechanism which I use to
+>> be able to sort outer inline pages according to the last modification
+>> date of their nested inline pages. The way I implemented it currently,
+>> though, doesn't use the existing hooks mechanism of ikiwiki (because
+>> it's something which I believe to be more efficiently done the way I
+>> implemented it) so I don't know how likely it is to be included
+>> upstream.
+
+>> For what it's worth, I think that my post_scan hook mechanism would work
+>> rather fine with your trail plugin. However, the case of the if
+>> directive is considerably more complicated, because the conditional
+>> can introduce a much stronger feedback effect in the pre/post scanning
+>> dependency. In fact, it's probably possible to build a couple of pages
+>> with vicious conditional dependency circles that would break/unbreak
+>> depending on which pass we are in. And I believe this is an intrinsic
+>> limitation of the system, which cannot be solved at all.