271 lines
12 KiB
Markdown
271 lines
12 KiB
Markdown
Hi,
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I am trying to build a template. The compilation of this template results in a weird exception. I have isolated the cause of the exception to the following point:
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If i have this in the template code:
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\[[!inline<br/>
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pages="\<TMPL_VAR SEL_PAGES\>"<br/>
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template=extract-entry<br/>
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\]]<br/>
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There is no problem at all. I can use the template with the desired result. But if I try to use this (just adding the "show" parameter):
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\[[!inline <br/>
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pages="\<TMPL_VAR SEL_PAGES>"<br/>
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template=extract-entry<br/>
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show=\<TMPL_VAR CNTPG><br/>
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\]]<br/>
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I get this exception on the Git bash console:
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<pre>
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$ git push
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Counting objects: 7, done.
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Delta compression using up to 8 threads.
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Compressing objects: 100% (4/4), done.
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Writing objects: 100% (4/4), 410 bytes, done.
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Total 4 (delta 3), reused 0 (delta 0)
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remote: From /home/b-odelama-com/source
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remote: eb1421e..5e1bac5 master -> origin/master
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remote: Argument "\x{3c}\x{54}..." isn't numeric in numeric lt (<) at /usr/share/perl5/IkiWiki/Plugin/inline.pm line 231.
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remote: Argument "\x{3c}\x{54}..." isn't numeric in numeric lt (<) at /usr/share/perl5/IkiWiki/Plugin/inline.pm line 231.
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To ssh://b-odelama-com@odelama-com.branchable.com/
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eb1421e..5e1bac5 master -> master
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</pre>
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Please, let me know what to do to avoid this kind of error.
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> When you add a template page `templates/foo.mdwn` for use
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> the [[ikiwiki/directive/template]] directive, two things happen:
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>
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> 1. `\[[!template id=foo ...]]` becomes available;
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> 2. a wiki page `templates/foo` is built, resulting in a HTML file,
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> typically `templates/foo/index.html`
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>
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> The warnings you're seeing are the second of these: when ikiwiki
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> tries to process `templates/foo.mdwn` as an ordinary page, without
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> interpreting the `<TMPL_VAR>` directives, `inline` receives invalid
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> input.
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>
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> This is a bit of a design flaw in [[plugins/template]] and
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> [[plugins/edittemplate]], I think - ideally it would be possible to
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> avoid parts of the page being interpreted when the page is being
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> rendered normally rather than being used as a template.
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>
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> There *is* a trick to avoid parts of the page being interpreted when
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> the page is being used as a template, while having them appear
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> when it's rendered as a page:
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>
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> <TMPL_IF FALSE>
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> <!-- This part only appears when being used as a page.
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> It assumes that you never set FALSE to a true value :-) -->
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> \[[!meta robots="noindex,nofollow"]]
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> This template is used to describe a thing. Parameters:
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> * name: the name of the thing
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> * size: the size of the thing
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> </TMPL_IF>
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>
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> The thing is called <TMPL_VAR name> and its size is <TMPL_VAR size>
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>
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> I suppose you could maybe extend that to something like this:
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>
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> <TMPL_IF FALSE>
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> <!-- This part only appears when being used as a page.
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> It assumes that you never set FALSE to a true value :-) -->
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> \[[!meta robots="noindex,nofollow"]]
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> This template is used to describe a thing. Parameters:
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> * name: the name of the thing
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> * size: the size of the thing
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> </TMPL_IF>
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>
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> <TMPL_IF FALSE>
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> \[[!if test="included() and !included()" then="""
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> </TMPL_IF>
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> <!-- This part only appears when being used as a template. It also
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> assumes that you never set FALSE to a true value, and it
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> relies on the [[ikiwiki/pagespec]] "included() and !included()"
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> never being true. -->
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> The thing is called <TMPL_VAR name> and its size is <TMPL_VAR size>
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> <TMPL_IF FALSE>
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> """]]
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> </TMPL_IF>
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>
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> but that's far harder than it ought to be!
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>
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> Perhaps the right solution would be to change how the template plugin
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> works, so that templates are expected to contain a new `definetemplate`
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> directive:
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>
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> This template is used to describe a thing. Parameters:
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> * name: the name of the thing
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> * size: the size of the thing
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>
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> \[[!definetemplate """
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> The thing is called <TMPL_VAR name> and its size is <TMPL_VAR size>
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> """]]
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>
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> with templates not containing a `\[[!definetemplate]]` being treated
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> as if the whole text of the page was copied into a `\[[!definetemplate]]`,
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> for backwards compatibility?
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>
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> --[[smcv]]
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>> OK, here is a branch implementing what I said. It adds the `definetemplate`
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>> directive to [[plugins/goodstuff]] as its last commit.
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>>
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>> Templates with the current strange semantics will still work, until
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>> IkiWiki breaks compatibility.
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>>
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>> Possible controversies:
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>>
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>> * Should the `definetemplate` plugin be core, or in goodstuff, or neither?
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>>
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>> * Should \[[!definetemplate]] be allowed on any page (with the implementation
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>> of `template("foo")` looking for a `definetemplate` in `templates/foo`,
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>> then a `definetemplate` in `foo`, then fall back to the current logic)?
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>> If not, should \[[!definetemplate]] raise an error when used on a page not
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>> in `templates/`, since it will have no practical effect there?
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>>
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>> * Is it OK to rely on `definetemplate` being enabled in the basewiki's
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>> templates?
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>>
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>> * Should the "use definetemplate" wording in the documentation of
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>> template and edittemplate be stronger? Should those plugins automatically
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>> load definetemplate?
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>>
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>> --[[smcv]]
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>>> this looks like a good idea to me.
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>>>
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>>> * i'd put it in core, and add a transition for the time compatibility gets
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>>> broken, provided the transitioning system will be used in that. templates
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>>> can't be expected to just work as markdown+ikiwiki too.
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>>>
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>>> (it being in core would also solve my qualms about `section => "web"` /
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>>> `\[[!tag type/web]]`).
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>>>
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>>> * if definetemplate gets deemed core, no "use definetemplate!" notes on the
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>>> template/edittemplate pages will be required any more.
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>>>
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>>> * first i was sceptical of the approach of re-running scan to make sure the
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>>> `my %templates` is filled, but it is indeed a practical solution.
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>>>
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>>> * the name "`definetemplate`" gives me the first impression that something
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>>> is assigned (as in `#define`), but actually it highlights a region in the
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>>> file. wouldn't "`templatebody`" be a better description of the meaning of
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>>> the directive?
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>>>
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>>> --[[chrysn]]
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>>>> Thanks for your feedback!
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>>>> Looking at its description on this wiki, I agree that `type/web` doesn't
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>>>> fit, and core does seem better. I like your `templatebody` suggestion,
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>>>> too, particularly if templates remain restricted to `/templates`.
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>>>> I'll try to come up with better wording for the documentation to say
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>>>> "use `templatebody`, like this", with a note about backwards
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>>>> compatibility later.
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>>>>
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>>>> Rationale for `my %templates`: yes it does seem a bit odd, but
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>>>> if I used `$pagestate{$tpage}{template}` instead of a `my` variable,
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>>>> I'd sometimes _still_ have to force a `scan`, because
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>>>> [[plugins/template]] has to expand the template at scan time so that
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>>>> it can contain links etc. - so I have to make sure that if the
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>>>> template has changed, it has already been scanned (scanning happens
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>>>> in random order, so that can't be guaranteed). This means there's
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>>>> no benefit in reading it back from the index, so it might as well
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>>>> just be in-memory.
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>>>>
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>>>> I suppose an alternative way to do it would be to remember what was
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>>>> passed to `needsbuild`, and only force a `scan` for templates that
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>>>> were in that list - which potentially reduces CPU time and I/O a
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>>>> little, in exchange for a bigger index. I could do that if Joey
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>>>> wants me to, but I think the current approach is simpler,
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>>>> so I'll stick with the current approach if it isn't vetoed.
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>>>> --[[smcv]]
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>>>>> @name: even outside `/templates`, `\[[!templatebody]]` would be
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>>>>> interpreted as "when this page is used as a template, this is what its
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>>>>> contents should be", and be suitable.
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>>>>>
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>>>>> @`%templates`: my surprise wasn't to it not being in `%pagestate`, but
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>>>>> rather that the `scan` function was used for it at all, rather than plain
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>>>>> directive parsing that ignores everything else -- but i agree that it's
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>>>>> the right thing to do in this situation.
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>>>>>
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>>>>> --[[chrysn]]
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----
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[[!template id=gitbranch author="[[smcv]]" branch=smcv/ready/templatebody
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browse=http://git.pseudorandom.co.uk/smcv/ikiwiki.git/shortlog/refs/heads/ready/templatebody]]
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[[!tag patch users/smcv/ready]]
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Branch and directive renamed to `ready/templatebody` as chrysn suggested.
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It's on-by-default now (or will be if that branch is merged).
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Joey, any chance you could review this?
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There is one known buglet: `template_syntax.t` asserts that the entire
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file is a valid HTML::Template, whereas it would ideally be doing the
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same logic as IkiWiki itself. I don't think that's serious. --[[smcv]]
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> Looking over this, I notice it adds a hash containing all scanned
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> files. This seems to me to be potentially a scalability problem on
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> rebuild of a site with many pages. Ikiwiki already keeps a lot
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> of info in memory, and this adds to it, for what is a fairly
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> minor reason. It seems to me there should be a way to avoid this. --[[Joey]]
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>> Maybe. Are plugins expected to cope with scanning the same
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>> page more than once? If so, it's just a tradeoff between
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>> "spend more time scanning the template repeatedly" and
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>> "spend more memory on avoiding it", and it would be OK to
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>> omit that, or reduce it to a set of scanned *templates*
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>> (in practice that would mean scanning each template twice
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>> in a rebuild). --s
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>>> [Commit f7303db5](http://source.ikiwiki.branchable.com/?p=source.git;a=commitdiff;h=f7303db5)
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>>> suggests that scanning the same page more than once is problematic,
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>>> so that solution is probably not going to work.
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>>>
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>>> The best idea I've come up with so far is to track whether
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>>> we're in the scan or render phase. If we're in the scan
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>>> phase, I think we do need to keep track of which pages
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>>> we've scanned, so we don't do them again? (Or perhaps that's
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>>> unnecessary - commit f7303db5 removed a scan call that's in
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>>> the render phase.) If we're in the render phase, we can assume
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>>> that all changed pages have been scanned already, so we can
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>>> drop the contents of `%scanned` and rely on a single boolean
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>>> flag instead.
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>>>
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>>> `%scanned` is likely to be no larger than `%rendered`, which
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>>> we already track, and whose useful lifetime does not overlap
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>>> with `%scanned` now. I was tempted to merge them both and call
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>>> the result `%done_in_this_phase`, but that would lead to really
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>>> confusing situations if a bug led to `render` being called sooner
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>>> than it ought to be.
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>>>
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>>> My ulterior motive here is that I would like to formalize
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>>> the existence of different phases of wiki processing - at the
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>>> moment there are at least two phases, namely "it's too soon to
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>>> match pagespecs reliably" and "everything has been scanned,
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>>> you may use pagespecs now", but those phases don't have names,
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>>> so [[plugins/write]] doesn't describe them.
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>>>
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>>> I'm also considering adding warnings
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>>> if people try to match a pagespec before scanning has finished,
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>>> which can't possibly guarantee the right result, as discussed in
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>>> [[conditional_preprocess_during_scan]]. My `wip-too-soon` branch
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>>> is a start towards that; the docwiki builds successfully, but
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>>> the tests that use IkiWiki internals also need updating to
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>>> set `$phase = PHASE_RENDER` before they start preprocessing. --s
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>>>> reviewing those modifications, i think this is a good way to go. along
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>>>> with warning about pagespecs evaluated in scan phase, i think it should be
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>>>> an error to invoke scan in the render phase; that would mean that
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>>>> `readtemplate` needs to check whether it's invoked as a scan or not to
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>>>> decide whether to scan the template page, but would be generally more
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>>>> robust for future plugin writing.
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>>>>
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>>>> **addendum**: if the new phase state is used to create warnings/errors
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>>>> about improper ikiwiki api use of plugins (which is something i'd
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>>>> advocate), that should likewise warn if `add_link` actually adds a link in
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>>>> the render phase. such a warning would have helped spotting the
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>>>> link-related [[template evaluation oddities]] earlier. --[[chrysn]]
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