I'd like to see some way to conditionally include wiki text based on whether the wiki enables or disables certain features. For example, formatting, could use [[!if (enabled smiley) """Also, because this wiki has the smiley plugin enabled, you can insert [[smileys]] and some other useful symbols."""]], and a standard template for plugins pages could check for the given plugin name to print "enabled" or "disabled".

Some potentially useful conditionals:

  • enabled pluginname
  • disabled pluginname
  • any pagespec: true if any of the pages in the PageSpec exist
  • all pagespec: true if all of the pages in the PageSpec exist
  • no pagespec or none pagespec: true if none of the pages in the PageSpec exist
  • thispage pagespec: true if pagespec includes the page getting rendered (possibly one including the page with this content on it).
  • sourcepage pagespec: true if pagespec includes the page corresponding to the file actually containing this content, rather than a page including it.
  • included: true if included on another page, via inline, sidebar, navbar, etc.

You may or may not want to include boolean operations (and, or, and not); if you do, you could replace disabled with not enabled, and no pagespec or none pagespec with not any pagespec (but you may want to keep the aliases for simplicity anyway). You also may or may not want to include an else clause; if so, you could label the text used if true as then.

Syntax could vary greatly here, both for the Directive and for the condition itself.

I think this is a good thing to consider, although conditionals tend to make everything a lot more complicated, so I also want to KISS, and not use too many of them.

I'd probably implement this using the same method as pagespecs, so 'and', 'or', '!', and paren groupings work.

It could be thought of as simply testing to see if a pagespec matches anything, using a slightly expanded syntax for the pagespec, which would also allow testing for things like link(somepage), created_before(somepage), etc.

That also gives us your "any pagespec" for free: "page or page or page". And for "all pagespec", you can do "page and page and page".

For plugins testing, maybe just use "enabled(name)"?

I'm not sure what the use cases are for thispage, sourcepage, and included. I don't know if the included test is even doable. I'd be inclined to not bother with these three unless there are use cases I'm not seeing.

As to the syntax, to fit it into standard preprocessor syntax, it would need to look something like this:

[[!if test="enabled(smiley)" """foo"""]]


PageSpec syntax seems perfect, and your proposed syntax for the if Directive looks fine to me.

PageSpecs don't give you none for free, since !foo/* as a boolean would mean "does any page not matching foo/* exist", not "does foo/* match nothing"; however, I don't really care much about none, since I just threw it in while brainstorming, and I don't know any compelling use cases for it.

enabled(pluginname) will work perfectly, and !enabled(pluginname) makes disabled unnecessary.

A few use cases for included, which I would really like to see:

  • On the sidebar page, you could say something like [[!if test="!included" """This page, without this help message, appears as a sidebar on all pages."""]]. The help text would then only appear on the sidebar page itself, not the sidebar included on all pages.

  • On blog entries, you could use included to implement a cut. (Please don't take that as an argument against. :) ) For instance, you could use included rather than toggle for the detailed changelogs of ikiwiki, or to embed an image as a link in the feed rather than an embedded image.

Some use cases for thispage:

  • You could use thispage to include or exclude parts of the sidebar based on the page you include it in. You can already use subpages/sidebar for subpages/*, but thispage seems more flexible, makes it trivial to have common portions rather than using inline with the raw option, and keeps the sidebar in one place.

  • You could use thispage to implement multiple different feeds for the same content with slightly different presentation. For instance, using templates for image inclusion, you could offer a feed with image links and a feed with embedded images. Similarly, using templates for cuts, you could offer a feed with cuts and a feed with full content in every post.

I don't have any particular attachment to sourcepage. It only makes sense as part of a template, since otherwise you know the source page when typing in the if.


This is now completely done! See conditional.


You rock mightily. --JoshTriplett

Is there a way to test features other than plugins? For example, to add to Markdown something like

[[!if  test="enabled(multimarkdown)" then="You can also use..."]]

(I tried it like that just to see if it would work, but I wasn't that lucky.) --ChapmanFlack

No, not supported. I really think that trying to conditionalise text on a page for multimarkdown is a path to madness or unreadability though. Perhaps it would be better to have .mmdwn files that can only contain multimarkdown? --Joey

Really, there was only one (or maybe two) pages I had in mind as appropriate places for conditional text based on multimarkdown—the underlay pages for 'markdown' and maybe also 'formatting', because those are the pages you look at when you're trying to find out how to mark stuff up for the wiki, so if MM is enabled, they need to at least mention it and have a link to the MM syntax guide.--ChapmanFlack