Available in a git repository branch.
Branch: jon/defaultmeta
Author: Jon

I'd like to define meta values to apply across all pages site-wide unless the pages define their own: default values for meta definitions essentially.

<snip old patch, see below for latest>

-- Jon

This doesn't support multiple-argument meta directives like link=x rel=y, or meta directives with special side-effects like updated.

The first could be solved (if you care) by a syntax like this:

meta_defaults => [
    { copyright => "© me" },
    { link => "about:blank", rel => "silly", },

The second could perhaps be solved by invoking meta::preprocess from within scan (which might be a simplification anyway), although this is complicated by the fact that some (but not all!) meta headers are idempotent.


Thanks for your comment. I've revised the patch to use the config syntax you suggest. I need to perform some more testing to make sure I've addressed the issues you highlight.

I had to patch part of IkiWiki core, the merge routine in Setup, because the use of possibly_foolish_untaint was causing the hashrefs at the deep end of the data structure to be converted into strings. The specific change I've made may not be acceptable, though -- I'd appreciate someone providing some feedback on that hunk!

Well, re that hunk, taint checking is currently disabled, but if the perl bug that disallows it is fixed and it is turned back on, the hash values will remain tainted, which will probably lead to problems.

I'm also leery of using such a complex data structure in config. The websetup plugin would be hard pressed to provide a UI for such a data structure. (It lacks even UI for a single hash ref yet, let alone a list.)

Also, it seems sorta wrong to have two so very different syntaxes to represent the same meta data. A user without a lot of experience will be hard pressed to map from a directive to this in the setup file.

All of which leads me to think the setup file could just contain a text that could hold meta directives. Which generalizes really to a text that contains any directives, and is, perhaps appended to the top of every page. Which nearly generalizes to the sidebar plugin, or perhaps something more general than that...

However, excessive generalization is the root of all evil, so I'm not necessarily saying that's a good idea. Indeed, my memory concerns below invalidate this idea pretty well. --Joey

<snip old patch>

-- Jon

Ok, I've had a bit of a think about this. There are currently 15 supported meta fields. Of these: title, licence, copyright, author, authorurl, and robots might make sense to define globally and override on a per-page basis.

Less so, description (due to its impact on map); openid (why would someone want more than one URI to act as an openid endpoint to the same place?); updated. I can almost see why someone might want to set a global updated value. Almost.

Not useful are permalink, date, stylesheet (you already have a global stylesheet), link, redir, and guid.

In other words, the limitations of my first patch that smcv outlined are only relevant to defined fields that you wouldn't want to specify a global default for anyway.

I generally agree with this. It is possible that meta would have a new field added, that takes parameters and make sense to use globally. (Indeed, this later happened to some extent with the sortas parameters being added to some metas.) --Joey

Due to this, and the added complexity of the second patch (having to adjust IkiWiki/Setup.pm), I think the first patch makes more sense. I've thus reverted to it here.

Is this merge-worthy?

<snip old patch>

-- Jon

Merry Christmas/festive season/happy new year folks. I've been away from ikiwiki for the break, and now I've returned to watching recentchanges. Hopefully I'll be back in the mix soon, too. In the meantime, Joey, have you had a chance to look at this yet? -- Jon

Ping :) Hi. Joey, would you consider this patch for the next ikiwiki release? -- Jon

For this to work with websetup and --dumpsetup, it needs to define the meta_* settings in the getsetup function.

I think this will be problematic with the current implementation of this patch. The datatype here is an array of hash references, with each hash having a variable (and arbitrary) number of key/value pairs. I can't think of an intuitive way of implementing a way of editing such a datatype in the web interface, let alone registering the option in getsetup.

Perhaps a limited set of defined meta values could be exposed via websetup (the obvious ones: author, copyright, license, etc.) -- Jon

I also have some concerns about both these patches, since both throw a lot of redundant data at meta, which then stores it in a very redundant way. Specifically, meta populates a per-page %metaheaders hash as well as storing per-page metadata in %pagestate. So, if you have a wiki with 10 thousand pages, and you add a 1k site-wide license text, that will bloat the memory usage of ikiwiki by in excess of 2 megabytes. It will also cause ikiwiki to write a similar amount more data to its state file which has to be loaded back in each run.

Seems that this could be managed much more efficiently by having meta special-case the site-wide settings, not store them in these per-page data structures, and just make them be used if no per-page metadata of the given type is present. --Joey

that should be easy enough to do. I will work on a patch. -- Jon

Hi — I've written a new patch which I hope addresses the concerns raised with the previous ones. The new approach is to hard-code in scan() which of the meta types are supported in the setup file. If one is defined, then scan() calls preprocess(), as smcv suggested, rather than stuffing redundant data into ikiwiki's data structures.

Two types supported in the setup file have optional arguments: author and title. These are supported by having special-cased setup keys meta_author_sortas and meta_title_sortas. Future expansion of the number of supported types, or addition of arguments to existing ones, can similarly be special-cased.

The setup data structure is no longer complicated with an array-of-hashes, which means this is suitable for exposing via websetup. getsetup() has been adjusted accordingly.

The patch can be found at the git branch described above. — Jon

I wish I could take pity on you and just merge this, but AFAICS it still suffers from the memory bloat described above. Specifically, when scan calls preprocess, it stores the metadata in %pagestate etc. --Joey

No pity required — but whoops, yes, that was a bit of a mistake ☺ I guess I'll have to split the current preprocess in half. — Jon

I've been taking another look at this today, as I'm very keen to close various open loops of mine in IkiWiki to move on and do some other stuff. However, I'm not actually using this at the moment, so whilst I think it's a good idea, I can't really motivate myself to fix it anymore. I guess for now, this should just rot. — Jon