ikiwiki/doc/bugs/recentchanges_feed_links.mdwn

(Moved from [[plugins/recentchanges/discussion]])

I've just upgraded to ikiwiki 2.50 with the `recentchanges` plugin enabled, and
figured out that I have to turn on `rss` in `ikiwiki.setup` in order to get the
recentchanges feed. Now the feed shows up, but the links in the feed go to the
change pages, e.g. `recentchanges/change_1700.html`.  I can see a `recentchanges`
directory created in the working copy, containing files like `change_1700._change`
but for some reason they are not getting htmlized and carried over. I can see
in `recentchanges.pm` that it explicitly registers an `htmlize` hook for the
`_change` type, but something isn't happening. I also see `return if $type=~/^_/;` in
`render()` in `Render.pm` so I guess the upshot is I'm not sure how this is
supposed to work; is there a bug here or just something I overlooked that I need
to turn on? --Chapman Flack

> It's a (minor) bug that recentchanges optimises away generating the
> change pages, but that the rss/atom feed still links to them. --[[Joey]]

>> Hmm, ok, what's the intended correct behavior? To really generate the
>> change pages, or to change the links in the feed to point somewhere else that's
>> not missing? If you can easily point me to the right neighborhood in the code
>> I might work on a patch for this. It may be a (minor) bug in the grand scheme
>> of things, but it does seem pretty goofy if you've just clicked an RSS link. :)
>> --Chap (p.s. should this be moved to bugs?)

>>> The latter -- I think making the permalink point to
>>> "recentchanges#someid" will probably work. Probably first by addressing the
>>> todo about [[todo/ability_to_force_particular_UUIDs_on_blog_posts]],
>>> and then by just using that new ability in the page. --[[Joey]]

>>>> <del title="Prerequisite done now?">Ah. The prerequisite todo looks like more than I'd like to take on.
>>>> In the meantime, would it be very involved to change whatever bug now
>>>> optimizes away the change pages, or to simply have all the links in the
>>>> feed point to the recentchanges page itself, with no fragment id?
>>>> Either would be a bit nicer than having broken links in the feed. --Chap</del>

>>>> Does the completion of that todo mean it would be straightforward to get
>>>> recentchanges working now?  Is it just that the recentchanges plugin
>>>> needs to generate `\[[!meta guid=something]]` into the internal files,
>>>> and the inline plugin would then generate working links in feeds?  How should
>>>> the guid be constructed? Something based on the rcs revision number?  I guess
>>>> I'm still not completely clear on your vision for how it ought to work. --Chap

>>>> My idea is to use `\[[meta guid="http://url/recentchanges#rev"]]`, with the
>>>> `#rev` anchor also included in the change file, and being the rcs's
>>>> internal revision id. Then the guid is globally unique, and actually
>>>> links to the change in the recentchanges page. And, when the change
>>>> has fallen off the page, the link will still go to the recentchanges page.
>>>> 
>>>> First, need to check that guids in rss and atom feeds can have anchors in
>>>> them, and that the anchor is treated as part of the guid. (If the guid
>>>> is interpreted as just "http://url/recentchanges", then it's
>>>> not a very good guid.) If using an anchor for a guid is a problem,
>>>> it could instead generate a random uuid, and use `\[[meta
>>>> guid="urn:uuid:<foo>" permalink="http://url/recentchanges"]]`

>>>>> I had a quick look into this after fixing the "prerequisite", but got
>>>>> bogged down in minor details. Anyway, I'd be happy to help.
>>>>> I think the guid stuff is actually fairly irrelevant, you just need
>>>>> `\[[!meta permalink]]` (and in fact you're using guid incorrectly, by
>>>>> expecting it to be treated as a link).
>>>>>
>>>>> My advice would be: first, fix the bug as reported, by
>>>>> using `\[[!meta permalink="http://blah/blah/blah#change-$rev"]]` (starting
>>>>> anchor names with a number isn't syntactically valid, if I remember
>>>>> correctly, so do have a prefix like "change-" or "rev-" or something).
>>>>>
>>>>> Then, optionally, force the guid too (although it defaults to the permalink
>>>>> anyway, so this shouldn't actually be necessary).
>>>>>
>>>>> Some more explanation of how guids work: it's actually easier to think
>>>>> about them in Atom terms than in RSS terms, since Atom has a clearer
>>>>> conceptual model.
>>>>>
>>>>> The `\[[!meta permalink]]` becomes the `<link>`
>>>>> element in Atom, which contains a link that users can follow; if it's not
>>>>> explicitly given, ikiwiki uses its idea of the page's URL.
>>>>>
>>>>> The `\[[!meta guid]]` becomes the `<id>` element in Atom, which contains an
>>>>> opaque, not-necessarily-resolvable identifier; if it's
>>>>> not explicitly given, ikiwiki uses the same URL as the `<link>`.
>>>>>
>>>>> In RSS the semantics aren't so clear-cut (which is part of why Atom exists!),
>>>>> but the way ikiwiki interprets them is:
>>>>>
>>>>> * `<link>` is the same as in Atom
>>>>> * if `\[[!meta guid]]` is explicitly given, put it in `<guid permalink="no">`
>>>>>   (the assumption in this case is that it's a UUID or something)
>>>>> * if `\[[!meta guid]]` is not explicitly given, copy the `<link>` into the `<guid>`
>>>>>
>>>>> I believe RSS aggregators (are meant to) compare `<guid>`s as opaque
>>>>> strings, so using an anchor there should be fine. Atom aggregators are certainly
>>>>> required to compare `<id>`s as opaque strings.
>>>>>
>>>>> --[[smcv]]

>>>>>> Here's my attempt at a [[patch]] for anchor-based change permalinks:
>>>>>> <http://pastie.org/295016>.
>>>>>> --[[JasonBlevins]], 2008-10-17

[[JasonBlevins]] nailed it, [[done]] --[[Joey]]