X-Git-Url: https://sipb.mit.edu/gitweb.cgi/ikiwiki.git/blobdiff_plain/6a0cffc41b0cac86d444138b05140f2043c96c80..9b5bf6ff85d7e738317aa87b68581082d9542394:/doc/todo/tracking_bugs_with_dependencies.mdwn diff --git a/doc/todo/tracking_bugs_with_dependencies.mdwn b/doc/todo/tracking_bugs_with_dependencies.mdwn index 464f68363..84b2448a6 100644 --- a/doc/todo/tracking_bugs_with_dependencies.mdwn +++ b/doc/todo/tracking_bugs_with_dependencies.mdwn @@ -206,12 +206,56 @@ account all comments above (which doesn't mean it is above reproach :) ). --[[W >> Because you have to define all the named pagespecs in the pagespec, you sometimes end up with very long pagespecs. I found it useful to split them over multiple lines. That didn't work at one point and I added the 's' to make it work. I may have further altered the regex since then to make the 's' redundant. Remove it and see if multi-line pagespecs still work. :) +>>> Well, I can tell you that multi-line pagespecs are supported w/o +>>> your patch .. I use them all the time. The reason I find your +>>> use of `/s` unlikely is because without it `\s` already matches +>>> a newline. Only if you want to treat a newline as non-whitespace +>>> is `/s` typically necessary. --[[Joey]] + > * Some changes of `@_` to `%params` in `pagespec_makeperl` do not > make sense to me. I don't see where \%params is defined and populated, > except with `\$params{specFunc}`. ->> I'm not a perl hacker. This was a mighty battle for me to get going. There is probably some battlefield carnage from my early struggles learning perl left here. ->> Part of this is that @_ / @params already existed as a way of passing in extra parameters. I didn't want to pollute that top level namespace - just at my own parameter (a hash) which contained the data I needed. +>> I'm not a perl hacker. This was a mighty battle for me to get going. +>> There is probably some battlefield carnage from my early struggles +>> learning perl left here. Part of this is that @_ / @params already +>> existed as a way of passing in extra parameters. I didn't want to +>> pollute that top level namespace - just at my own parameter (a hash) +>> which contained the data I needed. + +>>> I think I understand how the various `%params` +>>> (there's not just one) work in your code now, but it's really a mess. +>>> Explaining it in words would take pages.. It could be fixed by, +>>> in `pagespec_makeperl` something like: +>>> +>>> my %specFuncs; +>>> push @_, specFuncs => \%specFuncs; +>>> +>>> With that you have the hash locally available for populating +>>> inside `pagespec_makeperl`, and when the `match_*` functions +>>> are called the same hash data will be available inside their +>>> `@_` or `%params`. No need to change how the functions are called +>>> or do any of the other hacks. +>>> +>>> Currently, specFuncs is populated by building up code +>>> that recursively calls `pagespec_makeperl`, and is then +>>> evaluated when the pagespec gets evaluated. My suggested +>>> change to `%params` will break that, but that had to change +>>> anyway. +>>> +>>> It probably has a security hole, and is certianly inviting +>>> one, since the pagespec definition is matched by a loose regexp (`.*`) +>>> and then subject to string interpolation before being evaluated +>>> inside perl code. I recently changed ikiwiki to never interpolate +>>> user-supplied strings when translating pagespecs, and that +>>> needs to happen here too. The obvious way, it seems to me, +>>> is to not generate perl code, but just directly run perl code that +>>> populates specFuncs. + +>>>> I don't think this is as bad as you make out, but your addition of the +>>>> data array will break with the recursion my patch adds in pagespec_makeperl. +>>>> To fix that I'll need to pass a reference to that array into pagespec_makeperl. +>>>> I think I can then do the same thing to $params{specFuncs}. -- [[Will]] > * Seems that the only reason `match_glob` has to check for `~` is > because when a named spec appears in a pagespec, it is translated @@ -229,6 +273,23 @@ account all comments above (which doesn't mean it is above reproach :) ). --[[W >> call match_glob(). match_glob() in turn will handle the named spec. I tested this version briefly and it seemed to work. I remember looking at this again later and wondering if I had mis-understood >> some of the logic in match_link(), which might mean there are cases where you would need an explicit call to check_named_spec_existential() - I never checked it properly after having that thought. +>>> In the common case, `match_link` does not call `match_glob`, +>>> because the link target it is being asked to check for is a single +>>> page name, not a glob. + +>>>> A named pagespec should fall into the glob case. These two pagespecs should be the same: + + link(a*) + +>>>> and + + define(aStar, a*) and link(aStar) + +>>>> In the first case, we want the pagespec to match any page that links to a page matching the glob. +>>>> In the second case, we want the pagespec to match any page that links to a page matching the named spec. +>>>> match_link() was already doing existential part. The patches to this code were simply to remove the `lc()` +>>>> call from the named pagespec name. Can that `lc` be removed entirely? -- [[Will]] + > * Generally, the need to modify `match_*` functions so that they > check for and handle named pagespecs seems suboptimal, if > only because there might be others people may want to use named @@ -243,6 +304,9 @@ account all comments above (which doesn't mean it is above reproach :) ). --[[W >> Possibly. I'm not sure which I prefer between the current solution and that one. Each have advantages and disadvantages. >> It really isn't much code for the match functions to add a call to check_named_spec_existential(). +>>> But if a plugin adds its own match function, it has +>>> to explicitly call that code to support named pagespecs. + > * I need to check if your trick to avoid infinite recursion > works if there are two named specs that recursively > call one-another. I suspect it does, but will test this @@ -250,17 +314,96 @@ account all comments above (which doesn't mean it is above reproach :) ). --[[W >> It worked for me. :) +> * I also need to verify if memoizing the named pagespecs has +> really guarded against very expensive pagespecs DOSing the wiki.. + > --[[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. 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 break +>> Firstly, 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, +>>> then the second definition might be used at a point when +>>> it shouldn't (but I haven't verified that really happens). +>>> That could certianly be a show-stopper. --[[Joey]] + +>>>> Even if that works, this is a good argument for having a syntactic difference between named pagespecs and normal pages. +>>>> If you're joining two pagespecs with 'or', you don't want a named pagespec in the first part overriding a page name in the +>>>> second part. Oh, and I assume 'or' has the right operator precedence that "a and b or c" is "(a and b) or c", and not "a and (b or c)" -- [[Will]] + +>>>>> Looks like its bracketed in the code anyway... -- [[Will]] + +>> 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. + +>>>>> 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. + +>>>>> 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]] + ---- diff --git a/IkiWiki.pm b/IkiWiki.pm