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[ikiwiki] / doc / todo / tracking_bugs_with_dependencies.mdwn

I like the idea of [[tips/integrated_issue_tracking_with_ikiwiki]], and I do so on several wikis.  However, as far as I can tell, ikiwiki has no functionality which can represent dependencies between bugs and allow pagespecs to select based on dependencies.  For instance, I can't write a pagespec which selects all bugs with no dependencies on bugs not marked as done.  --[[JoshTriplett]]

> I started having a think about this.  I'm going to start with the idea that expanding
> the pagespec syntax is the way to attack this.  It seems that any pagespec that is going
> to represent "all bugs with no dependencies on bugs not marked as done" is going to
> need some way to represent "bugs not marked as done" as a collection of pages, and
> then represent "bugs which do not link to pages in the previous collection".
>
> One way to do this would be to introduce variables into the pagespec, along with
> universal and/or existential [[!wikipedia Quantification]].  That looks quite complex.
>
>> I thought about this briefly, and got about that far.. glad you got
>> further. :-) --[[Joey]]
> 
> Another option would be go with a more functional syntax.  The concept here would
> be to allow a pagespec to appear in a 'pagespec function' anywhere a page can.  e.g.
> I could pass a pagespec to `link()` and that would return true if there is a link to any
> page matching the pagespec.  This makes the variables and existential quantification
> implicit.  It would allow the example requested above:
>
>> `bugs/* and !*/Discussion and !link(bugs/* and !*/Discussion and !link(done))`
>
> Unfortunately, this is also going to make the pagespec parsing more complex because
> we now need to parse nested sets of parentheses to know when the nested pagespec
> ends, and that isn't a regular language (we can't use regular expression matching for
> easy parsing).
>
>> Also, it may cause ambiguities with page names that contain parens
>> (though some such ambigutities already exist with the pagespec syntax).
>
> One simplification of that would be to introduce some pagespec [[shortcuts]].  We could
> then allow pagespec functions to take either pages, or named pagespec shortcuts.  The
> pagespec shortcuts would just be listed on a special page, like current [[shortcuts]].
> (It would probably be a good idea to require that shortcuts on that page can only refer
> to named pagespecs higher up that page than themselves.  That would stop some
> looping issues...)  These shortcuts would be used as follows: when trying to match
> a page (without globs) you look to see if the page exists.  If it does then you have a
> match.  If it doesn't, then you look to see if a similarly named pagespec shortcut
> exists.  If it does, then you check that pagespec recursively to see if you have a match.
> The ordering requirement on named pagespecs stops infinite recursion.
>
> Does that seem like a reasonable first approach?
>
> -- [[Will]]

>> Having a separate page for the shortcuts feels unwieldly.. perhaps
>> instead the shortcut could be defined earlier in the scope of the same
>> pagespec that uses it?
>> 
>> Example: `define(~bugs, bugs/* and !*/Discussion) and define(~openbugs, ~bugs and !link(done)) and ~openbugs and !link(~openbugs)`

>>> That could work.  parens are only ever nested 1 deep in that grammar so it is regular and the current parsing would be ok.

>> Note that I made the "~" explicit, not implicit, so it could be left out. In the case of ambiguity between
>> a definition and a page name, the definition would win.

>>> That was my initial thought too :), but when implementing it I decided that requiring the ~ made things easier.  I'll probably require the ~ for the first pass at least.

>> So, equivilant example: `define(bugs, bugs/* and !*/Discussion) and define(openbugs, bugs and !link(done)) and openbugs and !link(openbugs)`
>> 
>> Re recursion, it is avoided.. but building a pagespec that is O(N^X) where N is the
>> number of pages in the wiki is not avoided. Probably need to add DOS prevention.
>>  --[[Joey]]

>>> If you memoize the outcomes of the named pagespecs you can make in O(N.X), no?
>>> -- [[Will]]

> One quick further thought.  All the above discussion assumes that 'dependency' is the
> same as 'links to', which is not really true.  For example, you'd like to be able to say
> "This bug does not depend upon [ [ link to other bug ] ]" and not have a dependency.
> Without having different types of links, I don't see how this would be possible.
>
> -- [[Will]]

Okie - I've had a quick attempt at this.  Initial patch attached.  This one doesn't quite work.
And there is still a lot of debugging stuff in there.

At the moment I've added a new preprocessor plugin, `definepagespec`, which is like
shortcut for pagespecs.  To reference a named pagespec, use `~` like this:

    [ [!definepagespec name="bugs" spec="bugs/* and !*/Discussion"]]
    [ [!definepagespec name="openbugs" spec="~bugs and !link(done)"]]
    [ [!definepagespec name="readybugs" spec="~openbugs and !link(~openbugs)"]]

At the moment the problem is in `match_link()` when we're trying to find a sub-page that
matches the appropriate page spec.  There is no good list of pages available to iterate over.

    foreach my $nextpage (keys %IkiWiki::pagesources)

does not give me a good list of pages.  I found the same thing when I was working on
this todo [[todo/Add_a_plugin_to_list_available_pre-processor_commands]].

> I'm not sure why iterating over `%pagesources` wouldn't work here, it's the same method
> used by anything that needs to match a pagespec against all pages..? --[[Joey]]

>> My uchecked hypothesis is that %pagesources is created after the refresh hook.
>> I've also been concerned about how globally defined pagespec shortcuts would interact with
>> the page dependancy system.  Your idea of internally defined shortcuts should fix that. -- [[Will]]

Immediately below is a patch for IkiWiki.pm.  Below that is a new plugin `definepagespec `
which behaves like `shortcut` for pagespecs.

----

diff --git a/IkiWiki.pm b/IkiWiki.pm
index e476521..1d2d48c 100644
--- a/IkiWiki.pm
+++ b/IkiWiki.pm
@@ -14,7 +14,7 @@ use open qw{:utf8 :std};
 use vars qw{%config %links %oldlinks %pagemtime %pagectime %pagecase
            %pagestate %renderedfiles %oldrenderedfiles %pagesources
            %destsources %depends %hooks %forcerebuild $gettext_obj
-           %loaded_plugins};
+           %loaded_plugins %named_pagespec};
 
 use Exporter q{import};
 our @EXPORT = qw(hook debug error template htmlpage add_depends pagespec_match
@@ -22,7 +22,7 @@ our @EXPORT = qw(hook debug error template htmlpage add_depends pagespec_match
                  displaytime will_render gettext urlto targetpage
                 add_underlay
                  %config %links %pagestate %renderedfiles
-                 %pagesources %destsources);
+                 %pagesources %destsources %named_pagespec);
 our $VERSION = 2.00; # plugin interface version, next is ikiwiki version
 our $version='unknown'; # VERSION_AUTOREPLACE done by Makefile, DNE
 my $installdir=''; # INSTALLDIR_AUTOREPLACE done by Makefile, DNE
@@ -1271,7 +1271,7 @@ sub loadindex () { #{{{
        %oldrenderedfiles=%pagectime=();
        if (! $config{rebuild}) {
                %pagesources=%pagemtime=%oldlinks=%links=%depends=
-               %destsources=%renderedfiles=%pagecase=%pagestate=();
+               %destsources=%renderedfiles=%pagecase=%pagestate=%named_pagespec=();
        }
        my $in;
        if (! open ($in, "<", "$config{wikistatedir}/indexdb")) {
@@ -1729,6 +1729,8 @@ sub match_glob ($$;@) { #{{{
        
        my $from=exists $params{location} ? $params{location} : '';
        
+       print "Matching glob $glob \n";
+       
        # relative matching
        if ($glob =~ m!^\./!) {
                $from=~s#/?[^/]+$##;
@@ -1736,6 +1738,18 @@ sub match_glob ($$;@) { #{{{
                $glob="$from/$glob" if length $from;
        }
 
+       if (substr($glob, 0, 1) eq '~') {
+               my $specname = substr($glob, 1);
+               print "Checking for pagespec named $specname \n";
+               if (exists $IkiWiki::named_pagespec{$specname}) {
+                       my $spec = $IkiWiki::named_pagespec{$specname};
+                       return IkiWiki::pagespec_match($page, $spec, %params);
+               } else {
+                       print "Couldn't find pagespec\n";
+                       return IkiWiki::FailReason->new("Page spec $specname referenced on page $page does not exist");
+               }
+       }
+
        my $regexp=IkiWiki::glob2re($glob);
        if ($page=~/^$regexp$/i) {
                if (! IkiWiki::isinternal($page) || $params{internal}) {
@@ -1756,11 +1770,36 @@ sub match_internal ($$;@) { #{{{
 
 sub match_link ($$;@) { #{{{
        my $page=shift;
-       my $link=lc(shift);
+       my $fulllink=shift;
+       my $link=lc($fulllink);
        my %params=@_;
 
+       print "Matching link $fulllink \n";
+       
        my $from=exists $params{location} ? $params{location} : '';
 
+       if (substr($fulllink, 0, 1) eq '~') {
+               my $specname = substr($fulllink, 1);
+               print "Checking link pagespec $specname \n";
+               if (exists $IkiWiki::named_pagespec{$specname}) {
+                       my $spec = $IkiWiki::named_pagespec{$specname};
+                       
+                       print "Checking all pages against $spec\n";
+                       
+                       foreach my $nextpage (keys %IkiWiki::pagesources) {
+                               print "Checking $nextpage against $spec\n";
+                               if (pagespec_match($nextpage, $spec, %params) && IkiWiki::PageSpec::match_link($page, $nextpage, %params)) {
+                                       return IkiWiki::SuccessReason->new("$page links to page $nextpage matching $link")
+                               }
+                       }
+                       
+                       return IkiWiki::FailReason->new("$page has no links to any pages that match $spec");
+               } else {
+                       print "Pagespec $specname not found\n";
+                       return IkiWiki::FailReason->new("$page cannot link to nonexistent spec name $specname");
+               }
+       }
+
        # relative matching
        if ($link =~ m!^\.! && defined $from) {
                $from=~s#/?[^/]+$##;

----

#!/usr/bin/perl
package IkiWiki::Plugin::definepagespec;

use warnings;
use strict;
use IkiWiki 2.00;

sub import { #{{{
        hook(type => "getsetup", id => "definepagespec", call => \&getsetup);
        hook(type => "refresh", id => "definepagespec", call => \&refresh);
        hook(type => "preprocess", id => "definepagespec", call => \&preprocess);
} #}}}

sub getsetup () { #{{{
        return
                plugin => {
                        safe => 1,
                        rebuild => undef,
                },
} #}}}

sub refresh () { #{{{
        # Preprocess the shortcuts page to get all the available shortcuts
        # defined before other pages are rendered.
        my $srcfile=srcfile("pagespecs.mdwn", 1);
        if (! defined $srcfile) {
                error(gettext("definepagespec plugin will not work without a pagespecs.mdwn"));
        }
        IkiWiki::preprocess("pagespecs", "pagespecs", readfile($srcfile));
} # }}}

sub preprocess (@) { #{{{
        my %params=@_;

        if (! defined $params{name} || ! defined $params{spec}) {
                error gettext("missing name or spec parameter");
        }

        $IkiWiki::named_pagespec{$params{name}} = $params{spec};

        #translators: This is used to display what shortcuts are defined.
        #translators: First parameter is the name of the shortcut, the second
        #translators: is an URL.
        return sprintf(gettext("pagespec %s refers to <i>%s</i>"), $params{name}, $params{spec});
} # }}}

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