>>>>
>>>> --[[Will]]
+>>>>> I think that should be supported by [[bugs/transitive_dependencies]].
+>>>>> At least in the current implementation, which considers each page
+>>>>> that is rendered to be changed, and rebuilds pages that are dependent
+>>>>> on it, in a loop. An alternate implementation, which could be faster,
+>>>>> is to construct a directed graph and traverse it just once. Sounds
+>>>>> like that would probably not support what you want to do.
+>>>>> --[[Joey]]
+
----
### Link dependencies
>>> of "!backlink(bogus)" where the page bogus doesn't exist? In this case, the page 'bogus' needs to be in the influence
>>> set even though it doesn't exist.
>>>
+>>>> I think you're right, this is a case that the current code is not
+>>>> handling. Actually, I made all the pagespecs return influences
+>>>> even if the influence was not present or did not match. But, it
+>>>> currently only records influences as dependencies when a pagespec
+>>>> successfully matches. Now I'm sure that is wrong, and I've removed
+>>>> that false optimisation. I've updated some of the below. --[[Joey]]
+>>>
>>> Also, I would really like the formalism to include the whole dependency system, not just any additions to it. That will make
>>> the whole thing much easier to reason about.
>>
#### Examples
* The pagespec "created_before(foo)" has an influence list that contains foo.
- The removal or (re)creation of foo changes what pages match it.
+ The removal or (re)creation of foo changes what pages match it. Note that
+ this is true even if the pagespec currently fails to match.
* The pagespec "foo" has an empty influence list. This is because a
modification/creation/removal of foo directly changes what the pagespec
>>> So, why don't the above influence lists contain the currently matched pages?
>>> Don't you need this to handle the removal problem? -- [[Will]]
+>>>> The removal problem is slightly confusingly named, since it does not
+>>>> affect pages that were matched by a glob and have been removed. Such
+>>>> pages can be handled without being influences, because ikiwiki knows
+>>>> they have been removed, and so can still match them against the
+>>>> pagespec, and see they used to match; and thus knows that the
+>>>> dependency has triggered.
+>>>>
+>>>> Maybe the thing to do is consider this an optimisation, where such
+>>>> pages are influences, but ikiwiki is able to implicitly find them,
+>>>> so they do not need to be explicitly stored. --[[Joey]]
+
* The pagespec "title(foo)" has an influence list that contains every page
that currently matches it. A change to any matching page can change its
title, making it not match any more, and so the list is needed due to the
- removal problem.
+ removal problem. A page that does not have a matching title is not an
+ influence, because modifying the page to change its title directly
+ changes what the pagespec matches.
* The pagespec "backlink(index)" has an influence list
that contains index (because a change to index changes the backlinks).
+ Note that this is true even if the backlink currently fails.
* The pagespec "link(done)" has an influence list that
contains every page that it matches. A change to any matching page can
> `or` short-circuits too, but the implementation correctly uses `|`,
> which I assume is what you meant. --[[smcv]]
+>> Er, yeah. --[[Joey]]
+
+----
+
+What about: "!link(done)"
+
+Specifically, I want to make sure it works now that I've changed
+`match_link` to only return a page as an influence if it *does*
+link to done.
+
+So, when matching against page P, that does not link to done,
+there are no influences, and the pagespec matches. If P is later
+changed to add a link to done, then the dependency resolver will directly
+notice that.
+
+When matching against page P, that does link to done, P
+is an influence, and the pagespec does not match. If P is later changed
+to not link to done, the influence will do its job.
+
+Looks good!
+
+----
+
+Here is a case where this approach has some false positives.
+
+"bugs/* and link(patch)"
+
+This finds as influences all pages that link to patch, even
+if they are not under bugs/, and so can never match.
+
+To fix this, the influence calculation would need to consider boolean
+operators. Currently, this turns into roughly:
+
+`FailReason() & SuccessReason(patch)`
+
+Let's say that the glob instead returns a HardFailReason, which when
+ANDed with another object, drops their influences. (But when ORed, combines
+them.) Fixes the above, but does it always work?
+
+"(bugs/* or link(patch)) and backlink(index)" =>
+`( HardFailReason() | SuccessReason(page) ) & SuccessReason(index)`` =>
+`SuccessReason(page & SuccessReason(index)` =>
+SuccessReason(page, index) => right
+
+"(bugs/* and link(patch)) or backlink(index)" =>
+`( HardFailReason() & SuccessReason(page) ) | SuccessReason(index)`` =>
+`HardFailReason() | SuccessReason(index)` =>
+`SuccessReason(index)` => right
+
+"!bugs/* and link(patch)" =>
+`HardFailReason() | SuccessReason(bugs/foo)` =>
+`HardFailReason()` => right
+
#### High-level Calculation and Storage
Naively calculating the full influence list for a pagespec requires trying
sipb-www / ikiwiki.git / blobdiff