X-Git-Url: https://sipb.mit.edu/gitweb.cgi/ikiwiki.git/blobdiff_plain/d3e0a54344a8ca5ac0a30af9f0a41cdb08df06ff..b6b7dc3a43266515822c31b177bfd26e8d59f359:/doc/todo/dependency_types.mdwn diff --git a/doc/todo/dependency_types.mdwn b/doc/todo/dependency_types.mdwn index f13f1448e..4bc38e9c0 100644 --- a/doc/todo/dependency_types.mdwn +++ b/doc/todo/dependency_types.mdwn @@ -156,20 +156,110 @@ 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. +---- + +#### Will's first pass feedback. + +If the API is going to be updated, then it would be good to make it forward compatible. +I'd like for the API to be extendible to what is useful for complex pagespecs, even if we +that is a little redundant at the moment. + +My attempt to play with this is in my git repo. [[!template id=gitbranch branch=origin/depends-spec author="[[will]]"]] +That branch is a little out of date, but if you just look at the changes in IkiWiki.pm you'll see the concept I was looking at. +I added an "add_depends_spec()" function that adds a dependency on the pagespec passed to it. If the set of matched pages +changes, then the dependent page is rebuilt. At the moment the implementation uses the same hack used by map and inline - +just add all the pages that currently exist as traditional content dependencies. + +Getting back to commenting on your proposal: + +Just talking about the definition of a "presence dependency" for the moment, and ignoring implementation. Is a +"presence dependency" supposed to cause an update when a page disappears? I assume so. Is a presence dependency +supposed to cause an update when a pages existence hasn't changed, but it no longer matches the pagespec. +(e.g. you use `created_before(test_page)` in a pagespec, and there was a page, `new_page`, that was created +after `test_page`. `new_page` will not match the spec. Now we'll delete and then re-create `test_page`. Now +`new_page` will match the spec, and yet `new_page` itself hasn't changed. Nor has its 'presence' - it was present +before and it is present now. Should this cause a re-build of any page that has a 'presence' dependency on the spec? + +I think that is another version of the problem you encountered with meta-data. + +In the longer term I was thinking we'd have to introduce a concept of 'internal pagespec dependencies'. Note that I'm +defining 'internal' pagespec dependencies differently to the pagespec dependencies I defined above. Perhaps an example: +If you had a pagespec that was `created_before(test_page)`, then you could list all pages created before `test_page` +with a `map` directive. The map directive would add a pagespec dependency on `created_before(test_page)`. +Internally, there would be a second page-spec parsing function that discovers which pages a given pagespec +depends on. As well as the function `match_created_before()`, we'd have to add a new function `depend_created_before()`. +This new function would return a list of pages, which when any of them change, the output of `match_created_before()` +would change. In this example, it would just return `test_page`. + +These lists of dependent pages could just be concatenated for every `match_...()` function in a pagespec - you can ignore +the boolean formula aspects of the pagespec for this. If a content dependency were added on these pages, then I think +the correct rebuilds would occur. + +In all, this is a surprisingly difficult problem to solve perfectly. Consider the following case: + +PageA.mdwn: + +> [ShavesSelf] + +PageB.mdwn + +> Doesn't shave self. + +ShavedByBob.mdwn: + +> [!include pages="!link(ShavesSelf)"] + +Does ShavedByBob.mdwn include itself? + +(Yeah - in IkiWiki currently links are included by include, but the idea holds. I had a good example a while back, but I can't think of it right now.) + +sigh. + +-- [[Will]] + ---- -Link dependencies: +### Link dependencies * `add_depends($page, $spec, links => 1, presence => 1)` adds a links + presence dependency. -* `refresh` only rebuilds a page with a links dependency if - pages matched by the pagespec gain or lose links. (What the link - actually points to may change independent of this, due to changes - elsewhere, without it firing.) +* 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]] +---- -TODO: How to determine if a pagespec is valid to be used with a links -dependency? Use the same simple pagespecs that are valid for presence -dependencies? +### the removal problem + +So far I have not addressed fixing the removal problem (which Will +discusses above). + +Summary of problem: A has a dependency on a pagespec such as +"bugs/* and !link(done)". B currently matches. Then B is updated, +in a way that makes A's dependency not match it (ie, it links to done). +Now A is not updated, because ikiwiki does not realize that it +depended on B before. + +This was worked around to fix [[bugs/inline_page_not_updated_on_removal]] +by inline and map adding explicit dependencies on each page that appears +on them. Then a change to B triggers the explicit dep. While this works, +it's 1) ugly 2) probably not implemented by all plugins that could +be affected by this problem (ie, linkmap) and 3) is most of the reason why +we grew the complication of `depends_simple`. + +One way to fix this is to include with each dependency, a list of pages +that currently match it. If the list changes, the dependency is triggered. + +Should be doable, but seems to involve a more work than +currently. Consider that a dependency on "bugs/*" currently +is triggered by just checking until *one* page is found to match it. +But to store the list, *every* page would have to be tried against it. +Unless the list can somehow be intelligently updated, looking at only the +changed pages.