path: root/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]]

>>>> Yeah, guess that'd work. :-)

> 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]]

>>> You're correct, the refresh hook is run very early, before pagesources
>>> is populated. (It will be partially populated on a refresh, but will
>>> not be updated to reflect new pages.) Agree that internally defined
>>> seems the way to go. --[[Joey]]

Immediately below is a patch which seems to basically work.  Lots of debugging code is still there
and it needs a cleanup, but I thought it worth posting at this point.  (I was having problems
with old style glob lists, so i just switched them off for the moment.)

The following three inlines work for me with this patch:

    Bugs:
    
    [ [!inline pages="define(~bugs, bugs/* and ! */Discussion) and ~bugs" archive="yes"]]
    
    OpenBugs:
    
    [ [!inline pages="define(~bugs, bugs/* and ! */Discussion) and define(~openbugs,~bugs and !link(done)) and ~openbugs" archive="yes"]]
    
    ReadyBugs:
    
    [ [!inline pages="define(~bugs, bugs/* and ! */Discussion) and define(~openbugs,~bugs and !link(done)) and define(~readybugs,~openbugs and !link(~openbugs)) and ~readybugs" archive="yes"]]

> Nice! Could the specfuncsref be passed in %params? I'd like to avoid
> needing to change the prototype of every pagespec function, since several
> plugins define them too. --[[Joey]]

>> Maybe - it needs more thought.  I also considered it when I was going though changing all those plugins :).
>> My concern was that `%params` can contain other user-defined parameters,
>> e.g. `link(target, otherparameter)`, and that means that the specFuncs could be clobbered by a user (or other
>> weird security hole).  I thought it better to separate it, but I didn't think about it too hard.  I might move it to
>> the first parameter rather than the second.  Ikiwiki is my first real perl hacking and I'm still discovering
>> good ways to write things in perl.
>>
>>>> `%params` contains the parameters passed to `pagespec_match`, not
>>>> user-supplied parameters. The user-supplied parameter to a function
>>>> like `match_glob()` or `match_link()` is passed in the second positional parameter. --[[Joey]]

>>>>> OK.  That seems reasonable then.  The only problem is that my PERLfu is not strong enough to make it
>>>>> work.  I really have to wonder what substance was influencing the designers of PERL...
>>>>> I can't figure out how to use the %params.  And I'm pissed off enough with PERL that I'm not going
>>>>> to try and figure it out any more.  There are two patches below now.  The first one uses an extra
>>>>> argument and works.  The second one tries to use %params and doesn't - take your pick :-). -- [[Will]]

>> What do you think is best to do about `is_globlist()`?  At the moment it requires that the 'second word', as
>> delimited by a space and ignoring parens, is 'and' or 'or'.  This doesn't hold in the above example pagespecs (so I just hard wired it to 0 to test my patch).
>> My thought was just to search for 'and' or 'or' as words anywhere in the pagespec.  Thoughts?

>>> Dunno, we could just finish deprecating it. Or change the regexp to
>>> skip over spaces in parens. (`/[^\s]+\s+([^)]+)/`) --[[Joey]]

>>>> I think I have a working regexp now.

>> Oh, one more thing.  In pagespec_translate (now pagespec_makeperl), there is a part of the regular expression for `# any other text`.
>> This contained `()`, which has no effect.  I replaced that with `\(\)`, but that is a change in the definition of pagespecs unrelated to the
>> rest of this patch. In a related change, commands were not able to contain `)` in their parameters.  I've extended that so the cannot
>> contain `(` or `)`.  -- [[Will]]

>>> `[^\s()]+` is a character class matching all characters not spaces or
>>> parens. Since the pervious terminals in the regexp consume most
>>> occurances of an open paren or close paren, it's unlikely for one to
>>> get through to that part of the regexp. For example, "foo()" will be
>>> matched by the command matcher; "(foo)" will be matched by the open
>>> paren literal terminal. "foo(" and "foo)" can get through to the
>>> end, and would be matched as a page name, if it didn't exclude parens.
>>>
>>> So why exclude them? Well, consider "foo and(bar and baz)". We don't
>>> want it to match "and(" as a page name!
>>> 
>>> Escaping the parens in the character class actually changes nothing; the
>>> changed character class still matches all characters not spaces or
>>> parens. (Try it!).
>>> 
>>> Re commands containing '(', I don't really see any reason not to
>>> allow that, unless it breaks something. --[[Joey]]

>>>> Oh, I didn't realise you didn't need to escape parens inside [].  All else I
>>>> I understood.  I have stopped commands from containing parens because
>>>> once you allow that then you might have a extra level of depth in the parsing
>>>> of define() statements. -- [[Will]]

>>> Updated patch.  Moved the specFuncsRef to the front of the arg list.  Still haven't thought through the security implications of
>>> having it in `%params`.  I've also removed all the debugging `print` statements.  And I've updated the `is_globlist()` function.
>>> I think this is ready for people other than me to have a play.  It is not well enough tested to commit just yet.
>>> -- [[Will]]

----

diff --git a/IkiWiki.pm b/IkiWiki.pm
index e476521..532aaf5 100644
--- a/IkiWiki.pm
+++ b/IkiWiki.pm
@@ -1524,7 +1524,16 @@ sub globlist_to_pagespec ($) { #{{{
 
 sub is_globlist ($) { #{{{
 	my $s=shift;
-	return ( $s =~ /[^\s]+\s+([^\s]+)/ && $1 ne "and" && $1 ne "or" );
+	return ! ($s =~ /
+			(^\s*
+				[^\s\(]+		# single item
+					(\(			# possibly with parens after it
+						([^\)]*	# with stuff inside those parens
+						(\([^\)]*\))*)*	# maybe even nested parens
+					\))?\s*$
+			) |
+				(\s and \s) | (\s or \s)	# or we find 'and' or 'or' somewhere
+			/x);
 } #}}}
 
 sub safequote ($) { #{{{
@@ -1605,7 +1614,7 @@ sub pagespec_merge ($$) { #{{{
 	return "($a) or ($b)";
 } #}}}
 
-sub pagespec_translate ($) { #{{{
+sub pagespec_makeperl ($) { #{{{
 	my $spec=shift;
 
 	# Support for old-style GlobLists.
@@ -1624,9 +1633,11 @@ sub pagespec_translate ($) { #{{{
 		|
 			\)		# )
 		|
-			\w+\([^\)]*\)	# command(params)
+			define\(\s*~\w+\s*,((\([^\(\)]*\)) | ([^\(\)]+))+\)	# define(~specName, spec) - spec can contain parens 1 deep
+		|
+			\w+\([^\(\)]*\)	# command(params) - params cannot contain parens
 		|
-			[^\s()]+	# any other text
+			[^\s\(\)]+	# any other text
 		)
 		\s*		# ignore whitespace
 	}igx) {
@@ -1640,16 +1651,23 @@ sub pagespec_translate ($) { #{{{
 		elsif ($word eq "(" || $word eq ")" || $word eq "!") {
 			$code.=' '.$word;
 		}
+		elsif ($word =~ /^define\(\s*~(\w+)\s*,(.*)\)$/) {
+			$code .= " (\$specFuncsRef->{$1}=";
+			$code .= "memoize(";
+			$code .= &pagespec_makeperl($2);
+			$code .= ")";
+			$code .= ") ";
+		}
 		elsif ($word =~ /^(\w+)\((.*)\)$/) {
 			if (exists $IkiWiki::PageSpec::{"match_$1"}) {
-				$code.="IkiWiki::PageSpec::match_$1(\$page, ".safequote($2).", \@_)";
+				$code.="IkiWiki::PageSpec::match_$1(\$specFuncsRef, \$page, ".safequote($2).", \@_)";
 			}
 			else {
 				$code.=' 0';
 			}
 		}
 		else {
-			$code.=" IkiWiki::PageSpec::match_glob(\$page, ".safequote($word).", \@_)";
+			$code.=" IkiWiki::PageSpec::match_glob(\$specFuncsRef, \$page, ".safequote($word).", \@_)";
 		}
 	}
 
@@ -1657,8 +1675,16 @@ sub pagespec_translate ($) { #{{{
 		$code=0;
 	}
 
+	return 'sub { my $specFuncsRef=shift; my $page=shift; '.$code.' }';
+} #}}}
+
+sub pagespec_translate ($) { #{{{
+	my $spec=shift;
+
+	my $code = pagespec_makeperl($spec);
+
 	no warnings;
-	return eval 'sub { my $page=shift; '.$code.' }';
+	return eval $code;
 } #}}}
 
 sub pagespec_match ($$;@) { #{{{
@@ -1673,7 +1699,7 @@ sub pagespec_match ($$;@) { #{{{
 
 	my $sub=pagespec_translate($spec);
 	return IkiWiki::FailReason->new("syntax error in pagespec \"$spec\"") if $@;
-	return $sub->($page, @params);
+	return $sub->({}, $page, @params);
 } #}}}
 
 sub pagespec_valid ($) { #{{{
@@ -1722,11 +1748,71 @@ sub new { #{{{
 
 package IkiWiki::PageSpec;
 
-sub match_glob ($$;@) { #{{{
+sub check_named_spec($$$;@) {
+	my $specFuncsRef=shift;
+	my $page=shift;
+	my $specName=shift;
+	my %params=@_;
+	
+	return IkiWiki::FailReason->new("Named page spec '$specName' is not valid")
+		unless (substr($specName, 0, 1) eq '~');
+	
+	$specName = substr($specName, 1);
+
+	if (exists $specFuncsRef->{$specName}) {
+		# remove the named spec from the spec refs
+		# when we recurse to avoid infinite recursion
+		my $sub = $specFuncsRef->{$specName};
+		$specFuncsRef->{$specName} = undef;
+		my $result = $sub->($specFuncsRef, $page, %params);
+		$specFuncsRef->{$specName} = $sub;
+		return $result;
+	} else {
+		return IkiWiki::FailReason->new("Page spec '$specName' does not exist");
+	}
+}
+
+sub check_named_spec_existential($$$$;@) {
+	my $specFuncsRef=shift;
+	my $page=shift;
+	my $specName=shift;
+	my $funcref=shift;
+	my %params=@_;
+	
+	return IkiWiki::FailReason->new("Named page spec '$specName' is not valid")
+		unless (substr($specName, 0, 1) eq '~');
+	$specName = substr($specName, 1);
+	
+	if (exists $specFuncsRef->{$specName}) {
+		# remove the named spec from the spec refs
+		# when we recurse to avoid infinite recursion
+		my $sub = $specFuncsRef->{$specName};
+		$specFuncsRef->{$specName} = undef;
+		
+		foreach my $nextpage (keys %IkiWiki::pagesources) {
+			if ($sub->($specFuncsRef, $nextpage, %params)) {
+				my $tempResult = $funcref->($specFuncsRef, $page, $nextpage, %params);
+				return $tempResult if ($tempResult);
+			}
+		}
+		
+		$specFuncsRef->{$specName} = $sub;
+		return IkiWiki::FailReason->new("No page in spec '$specName' was successfully matched");
+	} else {
+		return IkiWiki::FailReason->new("Named page spec '$specName' does not exist");
+	}
+}
+
+sub match_glob ($$$;@) { #{{{
+	my $specFuncsRef=shift;
 	my $page=shift;
 	my $glob=shift;
 	my %params=@_;
 	
+	if (substr($glob, 0, 1) eq '~') {
+		return check_named_spec($specFuncsRef, $page, $glob);
+	}
+
 	my $from=exists $params{location} ? $params{location} : '';
 	
 	# relative matching
@@ -1750,17 +1836,23 @@ sub match_glob ($$;@) { #{{{
 	}
 } #}}}
 
-sub match_internal ($$;@) { #{{{
-	return match_glob($_[0], $_[1], @_, internal => 1)
+sub match_internal ($$$;@) { #{{{
+	return match_glob(shift, shift, shift, @_, internal => 1)
 } #}}}
 
-sub match_link ($$;@) { #{{{
+sub match_link ($$$;@) { #{{{
+	my $specFuncsRef=shift;
 	my $page=shift;
-	my $link=lc(shift);
+	my $fulllink=shift;
+	my $link=lc($fulllink);
 	my %params=@_;
 
-	my $from=exists $params{location} ? $params{location} : '';
+	if (substr($fulllink, 0, 1) eq '~') {
+		return check_named_spec_existential($specFuncsRef, $page, $fulllink, \&match_link);
+	}
 
+	my $from=exists $params{location} ? $params{location} : '';
+	
 	# relative matching
 	if ($link =~ m!^\.! && defined $from) {
 		$from=~s#/?[^/]+$##;
@@ -1778,17 +1870,21 @@ sub match_link ($$;@) { #{{{
 		}
 		else {
 			return IkiWiki::SuccessReason->new("$page links to page $p matching $link")
-				if match_glob($p, $link, %params);
+				if match_glob($specFuncsRef, $p, $link, %params);
 		}
 	}
 	return IkiWiki::FailReason->new("$page does not link to $link");
 } #}}}
 
-sub match_backlink ($$;@) { #{{{
-	return match_link($_[1], $_[0], @_);
+sub match_backlink ($$$;@) { #{{{
+	my $specFuncsRef=shift;
+	my $page=shift;
+	my $backlink=shift;
+	return match_link($specFuncsRef, $backlink, $page, @_);
 } #}}}
 
-sub match_created_before ($$;@) { #{{{
+sub match_created_before ($$$;@) { #{{{
+	my $specFuncsRef=shift;
 	my $page=shift;
 	my $testpage=shift;
 
@@ -1805,7 +1901,8 @@ sub match_created_before ($$;@) { #{{{
 	}
 } #}}}
 
-sub match_created_after ($$;@) { #{{{
+sub match_created_after ($$$;@) { #{{{
+	my $specFuncsRef=shift;
 	my $page=shift;
 	my $testpage=shift;
 
@@ -1822,8 +1919,12 @@ sub match_created_after ($$;@) { #{{{
 	}
 } #}}}
 
-sub match_creation_day ($$;@) { #{{{
-	if ((gmtime($IkiWiki::pagectime{shift()}))[3] == shift) {
+sub match_creation_day ($$$;@) { #{{{
+	shift;
+	my $page=shift;
+	my $time=shift;
+
+	if ((gmtime($IkiWiki::pagectime{$page}))[3] == $time) {
 		return IkiWiki::SuccessReason->new('creation_day matched');
 	}
 	else {
@@ -1831,8 +1932,12 @@ sub match_creation_day ($$;@) { #{{{
 	}
 } #}}}
 
-sub match_creation_month ($$;@) { #{{{
-	if ((gmtime($IkiWiki::pagectime{shift()}))[4] + 1 == shift) {
+sub match_creation_month ($$$;@) { #{{{
+	shift;
+	my $page=shift;
+	my $time=shift;
+
+	if ((gmtime($IkiWiki::pagectime{$page}))[4] + 1 == $time) {
 		return IkiWiki::SuccessReason->new('creation_month matched');
 	}
 	else {
@@ -1840,8 +1945,12 @@ sub match_creation_month ($$;@) { #{{{
 	}
 } #}}}
 
-sub match_creation_year ($$;@) { #{{{
-	if ((gmtime($IkiWiki::pagectime{shift()}))[5] + 1900 == shift) {
+sub match_creation_year ($$$;@) { #{{{
+	shift;
+	my $page=shift;
+	my $time=shift;
+
+	if ((gmtime($IkiWiki::pagectime{$page}))[5] + 1900 == $time) {
 		return IkiWiki::SuccessReason->new('creation_year matched');
 	}
 	else {
diff --git a/IkiWiki/Plugin/attachment.pm b/IkiWiki/Plugin/attachment.pm
index f1f792a..a410e48 100644
--- a/IkiWiki/Plugin/attachment.pm
+++ b/IkiWiki/Plugin/attachment.pm
@@ -291,7 +291,8 @@ sub attachment_list ($) { #{{{
 
 package IkiWiki::PageSpec;
 
-sub match_user ($$;@) { #{{{
+sub match_user ($$$;@) { #{{{
+	shift;
 	shift;
 	my $user=shift;
 	my %params=@_;
@@ -311,7 +312,8 @@ sub match_user ($$;@) { #{{{
 	}
 } #}}}
 
-sub match_ip ($$;@) { #{{{
+sub match_ip ($$$;@) { #{{{
+	shift;
 	shift;
 	my $ip=shift;
 	my %params=@_;
diff --git a/IkiWiki/Plugin/conditional.pm b/IkiWiki/Plugin/conditional.pm
index 7716fce..c0dbb50 100644
--- a/IkiWiki/Plugin/conditional.pm
+++ b/IkiWiki/Plugin/conditional.pm
@@ -70,7 +70,8 @@ sub preprocess_if (@) { #{{{
 
 package IkiWiki::PageSpec;
 
-sub match_enabled ($$;@) { #{{{
+sub match_enabled ($$$;@) { #{{{
+	shift;
 	shift;
 	my $plugin=shift;
 	
@@ -83,13 +84,14 @@ sub match_enabled ($$;@) { #{{{
 	}
 } #}}}
 
-sub match_sourcepage ($$;@) { #{{{
+sub match_sourcepage ($$$;@) { #{{{
+	my $specFuncsRef=shift;
 	shift;
 	my $glob=shift;
 	my %params=@_;
 
 	return IkiWiki::FailReason->new("cannot match sourcepage") unless exists $params{sourcepage};
-	if (match_glob($params{sourcepage}, $glob, @_)) {
+	if (match_glob($specFuncsRef, $params{sourcepage}, $glob, @_)) {
 		return IkiWiki::SuccessReason->new("sourcepage matches $glob");
 	}
 	else {
@@ -97,13 +99,14 @@ sub match_sourcepage ($$;@) { #{{{
 	}
 } #}}}
 
-sub match_destpage ($$;@) { #{{{
+sub match_destpage ($$$;@) { #{{{
+	my $specFuncsRef=shift;
 	shift;
 	my $glob=shift;
 	my %params=@_;
 	
 	return IkiWiki::FailReason->new("cannot match destpage") unless exists $params{destpage};
-	if (match_glob($params{destpage}, $glob, @_)) {
+	if (match_glob($specFuncsRef, $params{destpage}, $glob, @_)) {
 		return IkiWiki::SuccessReason->new("destpage matches $glob");
 	}
 	else {
@@ -111,7 +114,8 @@ sub match_destpage ($$;@) { #{{{
 	}
 } #}}}
 
-sub match_included ($$;@) { #{{{
+sub match_included ($$$;@) { #{{{
+	shift;
 	shift;
 	shift;
 	my %params=@_;
diff --git a/IkiWiki/Plugin/filecheck.pm b/IkiWiki/Plugin/filecheck.pm
index 6f71be3..3592342 100644
--- a/IkiWiki/Plugin/filecheck.pm
+++ b/IkiWiki/Plugin/filecheck.pm
@@ -66,7 +66,8 @@ sub humansize ($) { #{{{
 
 package IkiWiki::PageSpec;
 
-sub match_maxsize ($$;@) { #{{{
+sub match_maxsize ($$$;@) { #{{{
+	shift;
 	my $page=shift;
 	my $maxsize=eval{IkiWiki::Plugin::attachment::parsesize(shift)};
 	if ($@) {
@@ -87,7 +88,8 @@ sub match_maxsize ($$;@) { #{{{
 	}
 } #}}}
 
-sub match_minsize ($$;@) { #{{{
+sub match_minsize ($$$;@) { #{{{
+	shift;
 	my $page=shift;
 	my $minsize=eval{IkiWiki::Plugin::attachment::parsesize(shift)};
 	if ($@) {
@@ -108,7 +110,8 @@ sub match_minsize ($$;@) { #{{{
 	}
 } #}}}
 
-sub match_mimetype ($$;@) { #{{{
+sub match_mimetype ($$$;@) { #{{{
+	shift;
 	my $page=shift;
 	my $wanted=shift;
 
@@ -138,7 +141,8 @@ sub match_mimetype ($$;@) { #{{{
 	}
 } #}}}
 
-sub match_virusfree ($$;@) { #{{{
+sub match_virusfree ($$$;@) { #{{{
+	shift;
 	my $page=shift;
 	my $wanted=shift;
 
@@ -180,7 +184,7 @@ sub match_virusfree ($$;@) { #{{{
 	}
 } #}}}
 
-sub match_ispage ($$;@) { #{{{
+sub match_ispage ($$$;@) { #{{{
 	my $filename=shift;
 
 	if (defined IkiWiki::pagetype($filename)) {
diff --git a/IkiWiki/Plugin/meta.pm b/IkiWiki/Plugin/meta.pm
index b2c85c8..788f248 100644
--- a/IkiWiki/Plugin/meta.pm
+++ b/IkiWiki/Plugin/meta.pm
@@ -263,6 +263,7 @@ sub pagetemplate (@) { #{{{
 
 sub match { #{{{
 	my $field=shift;
+	shift;
 	my $page=shift;
 	
 	# turn glob into a safe regexp
@@ -291,23 +292,23 @@ sub match { #{{{
 
 package IkiWiki::PageSpec;
 
-sub match_title ($$;@) { #{{{
+sub match_title ($$$;@) { #{{{
 	IkiWiki::Plugin::meta::match("title", @_);	
 } #}}}
 
-sub match_author ($$;@) { #{{{
+sub match_author ($$$;@) { #{{{
 	IkiWiki::Plugin::meta::match("author", @_);
 } #}}}
 
-sub match_authorurl ($$;@) { #{{{
+sub match_authorurl ($$$;@) { #{{{
 	IkiWiki::Plugin::meta::match("authorurl", @_);
 } #}}}
 
-sub match_license ($$;@) { #{{{
+sub match_license ($$$;@) { #{{{
 	IkiWiki::Plugin::meta::match("license", @_);
 } #}}}
 
-sub match_copyright ($$;@) { #{{{
+sub match_copyright ($$$;@) { #{{{
 	IkiWiki::Plugin::meta::match("copyright", @_);
 } #}}}
 
----

diff --git a/IkiWiki.pm b/IkiWiki.pm
index e476521..0751d56 100644
--- a/IkiWiki.pm
+++ b/IkiWiki.pm
@@ -1524,7 +1524,16 @@ sub globlist_to_pagespec ($) { #{{{
 
 sub is_globlist ($) { #{{{
 	my $s=shift;
-	return ( $s =~ /[^\s]+\s+([^\s]+)/ && $1 ne "and" && $1 ne "or" );
+	return ! ($s =~ /
+			(^\s*
+				[^\s(]+		# single item
+					(\(			# possibly with parens after it
+						([^)]*	# with stuff inside those parens
+						(\([^)]*\))*)*	# maybe even nested parens
+					\))?\s*$
+			) |
+				(\s and \s) | (\s or \s)	# or we find 'and' or 'or' somewhere
+			/x);
 } #}}}
 
 sub safequote ($) { #{{{
@@ -1605,7 +1614,7 @@ sub pagespec_merge ($$) { #{{{
 	return "($a) or ($b)";
 } #}}}
 
-sub pagespec_translate ($) { #{{{
+sub pagespec_makeperl ($) { #{{{
 	my $spec=shift;
 
 	# Support for old-style GlobLists.
@@ -1624,7 +1633,9 @@ sub pagespec_translate ($) { #{{{
 		|
 			\)		# )
 		|
-			\w+\([^\)]*\)	# command(params)
+			define\(\s*~\w+\s*,((\([^()]*\)) | ([^()]+))+\)	# define(~specName, spec) - spec can contain parens 1 deep
+		|
+			\w+\([^()]*\)	# command(params) - params cannot contain parens
 		|
 			[^\s()]+	# any other text
 		)
@@ -1640,16 +1651,23 @@ sub pagespec_translate ($) { #{{{
 		elsif ($word eq "(" || $word eq ")" || $word eq "!") {
 			$code.=' '.$word;
 		}
+		elsif ($word =~ /^define\(\s*~(\w+)\s*,(.*)\)$/) {
+			$code .= " (\$params{specFuncs}->{$1}=";	# (exists \$params{specFuncs}) && 
+			$code .= "memoize(";
+			$code .= &pagespec_makeperl($2);
+			$code .= ")";
+			$code .= ") ";
+		}
 		elsif ($word =~ /^(\w+)\((.*)\)$/) {
 			if (exists $IkiWiki::PageSpec::{"match_$1"}) {
-				$code.="IkiWiki::PageSpec::match_$1(\$page, ".safequote($2).", \@_)";
+				$code.="IkiWiki::PageSpec::match_$1(\$page, ".safequote($2).", \%params)";
 			}
 			else {
 				$code.=' 0';
 			}
 		}
 		else {
-			$code.=" IkiWiki::PageSpec::match_glob(\$page, ".safequote($word).", \@_)";
+			$code.=" IkiWiki::PageSpec::match_glob(\$page, ".safequote($word).", \%params)";
 		}
 	}
 
@@ -1657,23 +1675,36 @@ sub pagespec_translate ($) { #{{{
 		$code=0;
 	}
 
+	return 'sub { my $page=shift; my %params = @_; '.$code.' }';
+} #}}}
+
+sub pagespec_translate ($) { #{{{
+	my $spec=shift;
+
+	my $code = pagespec_makeperl($spec);
+
+	print "Spec '$spec' generated code '$code'\n";
+
 	no warnings;
-	return eval 'sub { my $page=shift; '.$code.' }';
+	return eval $code;
 } #}}}
 
 sub pagespec_match ($$;@) { #{{{
 	my $page=shift;
 	my $spec=shift;
 	my @params=@_;
+	my %params=@_;
 
 	# Backwards compatability with old calling convention.
 	if (@params == 1) {
-		unshift @params, 'location';
+		%params = { location => $params[1] };
 	}
 
+	$params{specFuncs} = {} unless exists $params{specFuncs};
+
 	my $sub=pagespec_translate($spec);
 	return IkiWiki::FailReason->new("syntax error in pagespec \"$spec\"") if $@;
-	return $sub->($page, @params);
+	return $sub->($page, %params);
 } #}}}
 
 sub pagespec_valid ($) { #{{{
@@ -1722,11 +1753,84 @@ sub new { #{{{
 
 package IkiWiki::PageSpec;
 
+sub check_named_spec($$;@) {
+	my $page=shift;
+	my $specName=shift;
+	my %params=@_;
+	
+	print "Checking named spec $specName\n";
+	
+	error("Unable to find specFuncs in params to check_named_spec()!") unless exists $params{specFuncs};
+	my $specFuncsRef=$params{specFuncs};
+	
+	print "A\n";
+	
+	return IkiWiki::FailReason->new("Named page spec '$specName' is not valid")
+		unless (substr($specName, 0, 1) eq '~');
+	
+	$specName = substr($specName, 1);
+
+	if (exists $specFuncsRef->{$specName}) {
+		# remove the named spec from the spec refs
+		# when we recurse to avoid infinite recursion
+		my $sub = $specFuncsRef->{$specName};
+		$specFuncsRef->{$specName} = undef;
+		my $result = $sub->($specFuncsRef, $page, %params);
+		$specFuncsRef->{$specName} = $sub;
+		return $result;
+	} else {
+		print "Invalid specname\n";
+		return IkiWiki::FailReason->new("Page spec '$specName' does not exist");
+	}
+}
+
+sub check_named_spec_existential($$$;@) {
+	my $page=shift;
+	my $specName=shift;
+	my $funcref=shift;
+	my %params=@_;
+	
+	print "(Existential) Checking named spec $specName\n";
+	
+	error("Unable to find specFuncs in params to check_named_spec()!") unless exists $params{specFuncs};
+	my $specFuncsRef=$params{specFuncs};
+	
+	print "B\n";
+	
+	return IkiWiki::FailReason->new("Named page spec '$specName' is not valid")
+		unless (substr($specName, 0, 1) eq '~');
+	$specName = substr($specName, 1);
+	
+	if (exists $specFuncsRef->{$specName}) {
+		# remove the named spec from the spec refs
+		# when we recurse to avoid infinite recursion
+		my $sub = $specFuncsRef->{$specName};
+		$specFuncsRef->{$specName} = undef;
+		
+		foreach my $nextpage (keys %IkiWiki::pagesources) {
+			if ($sub->($specFuncsRef, $nextpage, %params)) {
+				my $tempResult = $funcref->($page, $nextpage, %params);
+				return $tempResult if ($tempResult);
+			}
+		}
+		
+		$specFuncsRef->{$specName} = $sub;
+		return IkiWiki::FailReason->new("No page in spec '$specName' was successfully matched");
+	} else {
+		print "Invalid specname\n";
+		return IkiWiki::FailReason->new("Named page spec '$specName' does not exist");
+	}
+}
+
 sub match_glob ($$;@) { #{{{
 	my $page=shift;
 	my $glob=shift;
 	my %params=@_;
 	
+	if (substr($glob, 0, 1) eq '~') {
+		return check_named_spec($page, $glob, %params);
+	}
+
 	my $from=exists $params{location} ? $params{location} : '';
 	
 	# relative matching
@@ -1756,11 +1860,16 @@ sub match_internal ($$;@) { #{{{
 
 sub match_link ($$;@) { #{{{
 	my $page=shift;
-	my $link=lc(shift);
+	my $fulllink=shift;
+	my $link=lc($fulllink);
 	my %params=@_;
 
-	my $from=exists $params{location} ? $params{location} : '';
+	if (substr($fulllink, 0, 1) eq '~') {
+		return check_named_spec_existential($page, $fulllink, \&match_link, %params);
+	}
 
+	my $from=exists $params{location} ? $params{location} : '';
+	
 	# relative matching
 	if ($link =~ m!^\.! && defined $from) {
 		$from=~s#/?[^/]+$##;
@@ -1785,12 +1894,25 @@ sub match_link ($$;@) { #{{{
 } #}}}
 
 sub match_backlink ($$;@) { #{{{
-	return match_link($_[1], $_[0], @_);
+	my $page=shift;
+	my $backlink=shift;
+	my %params=@_;
+
+	if (substr($backlink, 0, 1) eq '~') {
+		return check_named_spec_existential($page, $backlink, \&match_backlink, %params);
+	}
+
+	return match_link($backlink, $page, %params);
 } #}}}
 
 sub match_created_before ($$;@) { #{{{
 	my $page=shift;
 	my $testpage=shift;
+	my %params=@_;
+
+	if (substr($testpage, 0, 1) eq '~') {
+		return check_named_spec_existential($page, $testpage, \&match_created_before, %params);
+	}
 
 	if (exists $IkiWiki::pagectime{$testpage}) {
 		if ($IkiWiki::pagectime{$page} < $IkiWiki::pagectime{$testpage}) {
@@ -1808,6 +1930,11 @@ sub match_created_before ($$;@) { #{{{
 sub match_created_after ($$;@) { #{{{
 	my $page=shift;
 	my $testpage=shift;
+	my %params=@_;
+
+	if (substr($testpage, 0, 1) eq '~') {
+		return check_named_spec_existential($page, $testpage, \&match_created_after, %params);
+	}
 
 	if (exists $IkiWiki::pagectime{$testpage}) {
 		if ($IkiWiki::pagectime{$page} > $IkiWiki::pagectime{$testpage}) {