69 lines
3.1 KiB
Markdown
69 lines
3.1 KiB
Markdown
[[!template id=gitbranch branch=chrismgray/exclusive-hooks author="[[chrismgray]]"]]
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Sometimes plugins register a function with `hook`, but they only want
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the function called with the content that they know how to deal with.
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Normally, this means that they call `pagetype` first thing in the
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function, determine if they know how to deal with the content, and
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only do anything if they do.
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> So, I can't find any plugins shipped with ikiwiki that actually do that.
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> Scan hooks are only ever passed the content of actual wiki pages, and
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> so unless a scan hook cares whether a page is written in markdown or
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> something else, it has no reason to care what the pagetype is. (Same for
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> linkify.) --[[Joey]]
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>> My [[org-mode|todo/org_mode]] external plugin (which will never
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>> really make sense to include with ikiwiki I think) does this. I
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>> think that most plugins defining alternate wiki syntaxes would as
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>> well. --[[chrismgray]]
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This is a bit wasteful in itself, but for external plugins, it's
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really bad. For functions like `scan` and `linkify`, where the entire
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page is sent back and forth over `stdout` and `stdin`, it really slows
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things down.
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Thus, I propose that there be a new optional parameter to `hook` that
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tells it that the function should only be called for files whose type
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is the same as the id of the plugin calling `hook`. I have called
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this parameter `exclusive` in my branch, but this might not be the
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best name.
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[[!tag patch]]
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> It's an interesting idea, but it might be more useful if it was more
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> generalized, say, by making it a filter, where the parameter is a regexp.
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>
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> --[[KathrynAndersen]]
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>> Would it make more sense as a pagespec? That might be a bit more hard
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>> to implement, but would certainly fix the naming issue.
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>>
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>> --[[chrismgray]]
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>>> Considering where it would be called, a pagespec might be overkill. --[[KathrynAndersen]]
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>>>> Pagespecs have some overhead themselves. Probably less than shipping
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>>>> the page content over stdio.
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>>>>
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>>>> Rather than putting filtering in the core of ikiwiki, I can think
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>>>> of two options. One is to make the main plugin a perl plugin, and
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>>>> have it call functions that are provided by another, external plugin.
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>>>> This is assuming you're using the other language because something
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>>>> is easy to do in it, not to avoid writing perl.
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>>>>
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>>>> Or, the external plugin interface could provide a version of `hook()`
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>>>> that does not pass the content parameter, but saves a copy that
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>>>> the plugin could request with a later rpc call. Assuming that
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>>>> it's really the overhead of serializing the page content, that's
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>>>> the problem, and not just the general overhead of making rpc calls
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>>>> for every page.. --[[Joey]]
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>>>>> Since the argument to `hook` is optional, the pagespec is only
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>>>>> interpreted if it is given. So there is no extra overhead
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>>>>> (beyond an unused `if` branch) in 99% of the cases.
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>>>>>
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>>>>> Rewriting the external plugin's shim using Perl is a good idea,
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>>>>> and one that I wish I had thought of earlier. On the other
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>>>>> hand, it doesn't set a great precedent about the usability of
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>>>>> external plugins. --[[chrismgray]]
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