Available in a git repository branch.
Branch: chrismgray/exclusive-hooks
Author: chrismgray

Sometimes plugins register a function with hook, but they only want the function called with the content that they know how to deal with. Normally, this means that they call pagetype first thing in the function, determine if they know how to deal with the content, and only do anything if they do.

So, I can't find any plugins shipped with ikiwiki that actually do that. Scan hooks are only ever passed the content of actual wiki pages, and so unless a scan hook cares whether a page is written in markdown or something else, it has no reason to care what the pagetype is. (Same for linkify.) --Joey

My org-mode external plugin (which will never really make sense to include with ikiwiki I think) does this. I think that most plugins defining alternate wiki syntaxes would as well. --chrismgray

This is a bit wasteful in itself, but for external plugins, it's really bad. For functions like scan and linkify, where the entire page is sent back and forth over stdout and stdin, it really slows things down.

Thus, I propose that there be a new optional parameter to hook that tells it that the function should only be called for files whose type is the same as the id of the plugin calling hook. I have called this parameter exclusive in my branch, but this might not be the best name.

It's an interesting idea, but it might be more useful if it was more generalized, say, by making it a filter, where the parameter is a regexp.


Would it make more sense as a pagespec? That might be a bit more hard to implement, but would certainly fix the naming issue.


Considering where it would be called, a pagespec might be overkill. --KathrynAndersen

Pagespecs have some overhead themselves. Probably less than shipping the page content over stdio.

Rather than putting filtering in the core of ikiwiki, I can think of two options. One is to make the main plugin a perl plugin, and have it call functions that are provided by another, external plugin. This is assuming you're using the other language because something is easy to do in it, not to avoid writing perl.

Or, the external plugin interface could provide a version of hook() that does not pass the content parameter, but saves a copy that the plugin could request with a later rpc call. Assuming that it's really the overhead of serializing the page content, that's the problem, and not just the general overhead of making rpc calls for every page.. --Joey

Since the argument to hook is optional, the pagespec is only interpreted if it is given. So there is no extra overhead (beyond an unused if branch) in 99% of the cases.

Rewriting the external plugin's shim using Perl is a good idea, and one that I wish I had thought of earlier. On the other hand, it doesn't set a great precedent about the usability of external plugins. --chrismgray