diff options
Diffstat (limited to 'doc/todo/tracking_bugs_with_dependencies.mdwn')
| -rw-r--r-- | doc/todo/tracking_bugs_with_dependencies.mdwn | 86 |
1 files changed, 5 insertions, 81 deletions
diff --git a/doc/todo/tracking_bugs_with_dependencies.mdwn b/doc/todo/tracking_bugs_with_dependencies.mdwn index 3894df5f6..5f3ece290 100644 --- a/doc/todo/tracking_bugs_with_dependencies.mdwn +++ b/doc/todo/tracking_bugs_with_dependencies.mdwn @@ -360,7 +360,10 @@ account all comments above (which doesn't mean it is above reproach :) ). --[[W > --[[Joey]] >> There is one issue that I've been thinking about that I haven't raised anywhere (or checked myself), and that is how this all interacts with page dependencies. ->> Firstly, I'm not sure anymore that the `pagespec_merge` function will continue to work in all cases. +>> +>>> I've moved the discussion of that to [[dependency_types]]. --[[Joey]] +>> +>> I'm not sure anymore that the `pagespec_merge` function will continue to work in all cases. >>> The problem I can see there is that if two pagespecs >>> get merged and both use `~foo` but define it differently, @@ -413,86 +416,7 @@ account all comments above (which doesn't mean it is above reproach :) ). --[[W >>> My [[remove-pagespec-merge|should_optimise_pagespecs]] branch has now >>> solved all this by deleting the offending function :-) --[[smcv]] ->> Secondly, it seems that there are two types of dependency, and ikiwiki ->> currently only handles one of them. The first type is "Rebuild this ->> page when any of these other pages changes" - ikiwiki handles this. ->> The second type is "rebuild this page when set of pages referred to by ->> this pagespec changes" - ikiwiki doesn't seem to handle this. I ->> suspect that named pagespecs would make that second type of dependency ->> more important. I'll try to come up with a good example. -- [[Will]] - ->>> Hrm, I was going to build an example of this with backlinks, but it ->>> looks like that is handled as a special case at the moment (line 458 of ->>> render.pm). I'll see if I can breapk ->>> things another way. Fixing this properly would allow removal of that special case. -- [[Will]] - ->>>> I can't quite understand the distinction you're trying to draw ->>>> between the two types of dependencies. Backlinks are a very special ->>>> case though and I'll be suprised if they fit well into pagespecs. ->>>> --[[Joey]] - ->>>>> The issue is that the existential pagespec matching allows you to build things that have similar ->>>>> problems to backlinks. ->>>>> e.g. the following inline: - - \[[!inline pages="define(~done, link(done)) and link(~done)" archive=yes]] - ->>>>> includes any page that links to a page that links to done. Now imagine I add a new link to 'done' on ->>>>> some random page somewhere - a page which some other page links to which didn't previously get included - the set of pages accepted by the pagespec, and hence the set of ->>>>> pages inlined, will change. But, there is no dependency anywhere on the page that I altered, so ->>>>> ikiwiki will not rebuild the page with the inline in it. What is happening is that the page that I altered affects ->>>>> the set of pages matched by the pagespec without itself being matched by the pagespec, and hence included in the dependency list. - ->>>>> To make this work well, I think you need to recognise two types of dependencies for each page (and no ->>>>> special cases for particular types of links, eg backlinks). The first type of dependency says, "The content of ->>>>> this page depends upon the content of these other pages". The `add_depends()` in the shortcuts ->>>>> plugin is of this form: any time the shortcuts page is edited, any page with a shortcut on it ->>>>> is rebuilt. The inline plugin also needs to add dependencies of this form to detect when the inlined ->>>>> content changes. By contrast, the map plugin does not need a dependency of this form, because it ->>>>> doesn't actually care about the content of any pages, just which pages it needs to include (which we'll handle next). - ->>>>> The second type of dependency says, "The content of this page depends upon the exact set of pages matched ->>>>> by this pagespec". The first type of dependency was about the content of some pages, the second type is about ->>>>> which pages get matched by a pagespec. This is the type of dependency tracking that the map plugin needs. ->>>>> If the set of pages matched by map pagespec changes, then the page with the map on it needs to be rebuilt to show a different list of pages. ->>>>> Inline needs this type of dependency as well as the previous type - This type handles a change in which pages ->>>>> are inlined, the previous type handles a change in the content of any of those pages. Shortcut does not need this type of ->>>>> dependency. Most of the places that use `add_depends()` seem to need this type of dependency rather than the first type. - ->>>>>> Note that inline and map currently achieve the second type of dependency by ->>>>>> explicitly calling `add_depends` for each page the displayed. ->>>>>> If any of those pages are removed, the regular pagespec would not ->>>>>> match them -- since they're gone. However, the explicit dependency ->>>>>> on them does cause them to match. It's an ugly corner I'd like to ->>>>>> get rid of. --[[Joey]] - ->>>>> Implementation Details: The first type of dependency can be handled very similarly to the current ->>>>> dependency system. You just need to keep a list of pages that the content depends upon. You could ->>>>> keep that list as a pagespec, but if you do this you might want to check that the pagespec doesn't change, ->>>>> possibly by adding a dependency of the second type along with the dependency of the first type. - ->>>>>> An example of the current system not tracking enough data is ->>>>>> described in [[bugs/transitive_dependencies]]. ->>>>>> --[[Joey]] - ->>>>> The second type of dependency is a little more tricky. For each page, we'd need a list of pagespecs that ->>>>> the page depended on, and for each pagespec you'd want to store the list of pages that currently match it. ->>>>> On refresh, you'd need to check each pagespec to see if the set of pages that match it has changed, and if ->>>>> that set has changed, then rebuild the dependent page(s). Oh, and for this second type of dependency, I ->>>>> don't think you can merge pagespecs. If I wanted to know if either "\*" or "link(done)" changes, then just checking ->>>>> to see if the set of pages matched by "\* or link(done)" changes doesn't work. - ->>>>> The current system works because even though you usually want dependencies of the second type, the set of pages ->>>>> referred to by a pagespec can only change if one of those pages itself changes. i.e. A dependency check of the ->>>>> first type will catch a dependency change of the second type with current pagespecs. ->>>>> This doesn't work with backlinks, and it doesn't work with existential matching. Backlinks are currently special-cased. I don't know ->>>>> how to special-case existential matching - I suspect you're better off just getting the dependency tracking right. - ->>>>> I also tried to come up with other possible solutions: e.g. can we find the dependencies for a pagespec? That ->>>>> would be the set of pages where a change on one of those pages could lead to a change in the set of pages matched by the pagespec. ->>>>> For old-style pagespecs without backlinks, the dependency set for a pagespec is the same as the set of pages the pagespec matches. ->>>>> Unfortunately, with existential matching, the set of pages that each ->>>>> pagespec depends upon can quickly become "*", which is not very useful. -- [[Will]] + Patch updated to use closures rather than inline generated code for named pagespecs. Also includes some new use of ErrorReason where appropriate. -- [[Will]] |