For some time now, in circumstances that I've had enormous troubles trying to track, I've seen feeds getting removed by ikiwiki when apparently unrelated pages got changed, with the message:
removing somepath/somepage/somefeed, no longer built by some/unrelated/page
I've finally been able to find how and why it happens. The situation is the following:
- page A has an inline directive that (directly) generates a feed F
- page B inlines A, thus (indirectly) generating F again
- page B is rendered after page A
The feed removal happens when changes are made to prevent B from inlining A; for example, because B is a tag page and A is untagged B, or because B includes A through a pagespec that no longer matches A. In this case, this happens:
- page A is built, rendering F
- page B is built, not rendering F, which it used to render
- F is removed because it is not built by B anymore
Note that although this issue is triggered (for me) from the changes I proposed last year to allow feed generation from nested inlines coalescing it to be page-based instead of destpage-based (bb8f76a4a04686def8cc6f21bcca80cb2cc3b2c9 and 72c8f01b36c841b0e83a2ad7ad1365b9116075c5) there is potential for it popping up in other cases.
Specifically, the logic for the removal of dependent pages currently relies on the assumption that each output has a single generator. My changes caused this assumption to be violated, hence the error, but other cases may pop up for other plugins in the future.
I have a [patch] fixing this issue (for feeds specifically, i.e. only
the problem I am actually having) on top of my mystuff branch, but
since that also has heaps of other unrelated stuff, you may want to just
pick it from my gitweb.
The patch changes the will_render() for feeds to be based on the page
rather than on the destpage, matching the fact that for nested inlines
it's the inner page that is ultimately responsible for generating the
feed.
I've noticed that it requires at least two full rebuilds before the index is again in a sensible state. (On the first rebuild, all feeds from nested inlines are actually removed.)
While the patch is needed because there are legitimate cases in which nested feeds are needed (for example, I have an index page that inlines index pages for subsection of my site, and I want those feed from being visible), there are other cases when one may want to skip feed generation from nested inlines.