oops

[git.ikiwiki.info.git] / doc / todo / tracking_bugs_with_dependencies.mdwn

diff --git a/doc/todo/tracking_bugs_with_dependencies.mdwn b/doc/todo/tracking_bugs_with_dependencies.mdwn
index a2287cdf4ae87001b48a013858a3729412045c6b..456dadad08be2de7c02a3ac6aad6e1efd0dee548 100644 (file)
--- a/doc/todo/tracking_bugs_with_dependencies.mdwn
+++ b/doc/todo/tracking_bugs_with_dependencies.mdwn
@@ -1,3 +1,5 @@
+[[!tag patch patch/core]]
+

 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
 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


@@ -11,6 +13,8 @@ I like the idea of [[tips/integrated_issue_tracking_with_ikiwiki]], and I do so
 >
 >> I thought about this briefly, and got about that far.. glad you got
 >> further. :-) --[[Joey]]
 >
 >> I thought about this briefly, and got about that far.. glad you got
 >> further. :-) --[[Joey]]

+
+>> Or, one [[!taglink could_also_refer|pagespec_in_DL_style]] to the language of [[!wikipedia description logics]]: their formulas actually define classes of objects through quantified relations to other classes. --Ivan Z.

 > 
 > 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.
 > 
 > 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.


@@ -58,6 +62,7 @@ I like the idea of [[tips/integrated_issue_tracking_with_ikiwiki]], and I do so
 
 >> So, equivilant example: `define(bugs, bugs/* and !*/Discussion) and define(openbugs, bugs and !link(done)) and openbugs and !link(openbugs)`
 >> 
 
 >> 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]]
 >> 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]]


@@ -67,13 +72,18 @@ I like the idea of [[tips/integrated_issue_tracking_with_ikiwiki]], and I do so
 
 >>>> Yeah, guess that'd work. :-)
 
 
 >>>> Yeah, guess that'd work. :-)
 

-> One quick further thought.  All the above discussion assumes that 'dependency' is the
+> <a id="another_kind_of_links" />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]]
 
 > 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]]
 

+>> I saw that this issue is targeted at by the work on [[structured page data#another_kind_of_links]]. --Ivan Z.
+
+>>> It's fixed now; links can have a type, such as "tag", or "dependency", 
+>>> and pagespecs can match links of a given typo. --[[Joey]] 
+

 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.
 
 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.
 


@@ -136,7 +146,13 @@ The following three inlines work for me with this patch:
 >>>> `%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]]
 >>>> `%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?
 >> 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?


@@ -144,6 +160,8 @@ The following three inlines work for me with this patch:
 >>> Dunno, we could just finish deprecating it. Or change the regexp to
 >>> skip over spaces in parens. (`/[^\s]+\s+([^)]+)/`) --[[Joey]]
 
 >>> 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
 >> 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


@@ -167,467 +185,496 @@ The following three inlines work for me with this patch:
 >>> Re commands containing '(', I don't really see any reason not to
 >>> allow that, unless it breaks something. --[[Joey]]
 
 >>> 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]]
 
 >>> 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]]
 

+I've lost track of the indent level, so I'm going back to not indented - I think this is a working [[patch]] taking into
+account all comments above (which doesn't mean it is above reproach :) ).  --[[Will]]
+
+> Very belated code review of last version of the patch:
+> 
+> * `is_globlist` is no longer needed
+
+>> Good :)
+
+> * I don't understand why the pagespec match regexp is changed
+>   from having flags `igx` to `ixgs`. Don't see why you
+>   want `.` to match '\n` in it, and don't see any `.` in the regexp 
+>   anyway?
+
+>> Because you have to define all the named pagespecs in the pagespec, you sometimes end up with very long pagespecs.  I found it useful to split them over multiple lines.  That didn't work at one point and I added the 's' to make it work.  I may have further altered the regex since then to make the 's' redundant.  Remove it and see if multi-line pagespecs still work. :)
+
+>>> Well, I can tell you that multi-line pagespecs are supported w/o
+>>> your patch .. I use them all the time. The reason I find your
+>>> use of `/s` unlikely is because without it `\s` already matches
+>>> a newline. Only if you want to treat a newline as non-whitespace
+>>> is `/s` typically necessary. --[[Joey]] 
+
+> * Some changes of `@_` to `%params` in `pagespec_makeperl` do not
+>   make sense to me. I don't see where \%params is defined and populated,
+>   except with `\$params{specFunc}`.
+
+>> I'm not a perl hacker.  This was a mighty battle for me to get going.
+>> There is probably some battlefield carnage from my early struggles
+>> learning perl left here. Part of this is that @_ / @params already
+>> existed as a way of passing in extra parameters.  I didn't want to
+>> pollute that top level namespace - just at my own parameter (a hash)
+>> which contained the data I needed.
+
+>>> I think I understand how the various `%params`
+>>> (there's not just one) work in your code now, but it's really a mess.
+>>> Explaining it in words would take pages.. It could be fixed by,
+>>> in `pagespec_makeperl` something like:
+>>> 
+>>>    my %specFuncs;
+>>>    push @_, specFuncs => \%specFuncs;
+>>> 
+>>> With that you have the hash locally available for populating
+>>> inside `pagespec_makeperl`, and when the `match_*` functions
+>>> are called the same hash data will be available inside their
+>>> `@_` or `%params`. No need to change how the functions are called
+>>> or do any of the other hacks.
+>>>
+>>> Currently, specFuncs is populated by building up code
+>>> that recursively calls `pagespec_makeperl`, and is then
+>>> evaluated when the pagespec gets evaluated. My suggested
+>>> change to `%params` will break that, but that had to change 
+>>> anyway.
+>>>
+>>> It probably has a security hole, and is certianly inviting
+>>> one, since the pagespec definition is matched by a loose regexp (`.*`)
+>>> and then subject to string interpolation before being evaluated
+>>> inside perl code. I recently changed ikiwiki to never interpolate
+>>> user-supplied strings when translating pagespecs, and that
+>>> needs to happen here too. The obvious way, it seems to me,
+>>> is to not generate perl code, but just directly run perl code that
+>>> populates specFuncs.
+
+>>>> I don't think this is as bad as you make out, but your addition of the
+>>>> data array will break with the recursion my patch adds in pagespec_makeperl.
+>>>> To fix that I'll need to pass a reference to that array into pagespec_makeperl.
+>>>> I think I can then do the same thing to $params{specFuncs}.  -- [[Will]]
+
+>>>>> You're right -- I did not think the recursive case through.
+>>>>> --[[Joey]] 
+
+> * Seems that the only reason `match_glob` has to check for `~` is
+>   because when a named spec appears in a pagespec, it is translated
+>   to `match_glob("~foo")`. If, instead, `pagespec_makeperl` checked
+>   for named specs, it could convert them into `check_named_spec("foo")`
+>   and avoid that ugliness.
+
+>> Yeah - I wanted to make named specs syntactically different on my first pass.  You are right in that this could be made a fallback - named specs always override pagenames.
+
+> * The changes to `match_link` seem either unecessary, or incomplete.
+>   Shouldn't it check for named specs and call
+>   `check_named_spec_existential`?
+
+>>  An earlier version did.  Then I realised it wasn't actually needed in that case - match_link() already included a loop that was like a type of existential matching.  Each time through the loop it would
+>> call match_glob().  match_glob() in turn will handle the named spec.  I tested this version briefly and it seemed to work.  I remember looking at this again later and wondering if I had mis-understood
+>> some of the logic in match_link(), which might mean there are cases where you would need an explicit call to check_named_spec_existential() - I never checked it properly after having that thought.
+
+>>> In the common case, `match_link` does not call `match_glob`,
+>>> because the link target it is being asked to check for is a single
+>>> page name, not a glob.
+
+>>>> A named pagespec should fall into the glob case.  These two pagespecs should be the same:
+
+    link(a*)
+
+>>>> and
+
+    define(aStar, a*) and link(~aStar)
+
+>>>> In the first case, we want the pagespec to match any page that links to a page matching the glob.
+>>>> In the second case, we want the pagespec to match any page that links to a page matching the named spec.
+>>>> match_link() was already doing existential part.  The patches to this code were simply to remove the `lc()`
+>>>> call from the named pagespec name.  Can that `lc` be removed entirely? -- [[Will]]
+
+>>>>> I think we could get rid of it. `bestlink` will lc it itself
+>>>>> if the uppercase version does not exist; `match_glob` matches
+>>>>> insensitively.
+>>>>> --[[Joey]] 
+
+> * Generally, the need to modify `match_*` functions so that they
+>   check for and handle named pagespecs seems suboptimal, if
+>   only because there might be others people may want to use named
+>   pagespecs with. It would be possible to move this check
+>   to `pagespec_makeperl`, by having it check if the parameter
+>   passed to a pagespec function looked like a named pagespec.
+>   The only issue is that some pagespec functions take a parameter
+>   that is not a page name at all, and it could be weird
+>   if such a parameter were accidentially interpreted as a named
+>   pagespec. (But, that seems unlikely to happen.)
+
+>> Possibly.  I'm not sure which I prefer between the current solution and that one.  Each have advantages and disadvantages.
+>> It really isn't much code for the match functions to add a call to check_named_spec_existential().
+
+>>> But if a plugin adds its own match function, it has
+>>> to explicitly call that code to support named pagespecs.
+
+>>>> Yes, and it can do that in just three lines of code.  But if we automatically check for named pagespecs all the time we
+>>>> potentially break any matching function that doesn't accept pages, or wants to use multiple arguments.
+
+>>>>> 3 lines of code, plus the functions called become part of the API,
+>>>>> don't forget about that..
+>>>>>
+>>>>> Yes, I think that is the tradeoff, the question is whether to export
+>>>>> the additional complexity needed for that flexability.
+>>>>>
+>>>>> I'd be suprised if multiple argument pagespecs become necessary..
+>>>>> with the exception of this patch there has been no need for them yet.
+>>>>>
+>>>>> There are lots of pagespecs that take data other than pages,
+>>>>> indeed, that's really the common case. So far, none of them 
+>>>>> seem likely to take data that starts with a `~`. Perhaps
+>>>>> the thing to do would be to check if `~foo` is a known,
+>>>>> named pagespec, and if not, just pass it through unchanged.
+>>>>> Then there's little room for ambiguity, and this also allows
+>>>>> pagespecs like `glob(~foo*)` to match the literal page `~foo`.
+>>>>> (It will make pagespec_merge even harder tho.. see below.)
+>>>>> --[[Joey]] 
+
+>>>>>> I've already used multi-argument pagespec match functions in
+>>>>>> my data plugin.  It is used for having different types of links.  If
+>>>>>> you want to have multiple types of links, then the match function
+>>>>>> for them needs to take both the link name and the link type.
+>>>>>> I'm trying to think of a way we could have both - automatically
+>>>>>> handle the existential case unless the function indicates somehow
+>>>>>> that it'll do it itself.  Any ideas?  -- [[Will]]
+
+> * I need to check if your trick to avoid infinite recursion
+>   works if there are two named specs that recursively
+>   call one-another. I suspect it does, but will test this
+>   myself..
+
+>> It worked for me. :)
+
+> * I also need to verify if memoizing the named pagespecs has
+>   really guarded against very expensive pagespecs DOSing the wiki..
+
+> --[[Joey]] 
+
+>>  There is one issue that I've been thinking about that I haven't raised anywhere (or checked myself), and that is how this all interacts with page dependencies.
+>> 
+>>> I've moved the discussion of that to [[dependency_types]]. --[[Joey]] 
+>>
+>>  I'm not sure anymore that the `pagespec_merge` function will continue to work in all cases.
+
+>>> The problem I can see there is that if two pagespecs
+>>> get merged and both use `~foo` but define it differently,
+>>> then the second definition might be used at a point when
+>>> it shouldn't (but I haven't verified that really happens).
+>>> That could certianly be a show-stopper. --[[Joey]] 
+
+>>>> I think this can happen in the new closure based code.  I don't think this could happen in the old code.  -- [[Will]]
+
+>>>> Even if that works, this is a good argument for having a syntactic difference between named pagespecs and normal pages.
+>>>> If you're joining two pagespecs with 'or', you don't want a named pagespec in the first part overriding a page name in the
+>>>> second part.  Oh, and I assume 'or' has the right operator precedence that "a and b or c" is "(a and b) or c", and not "a and (b or c)" -- [[Will]]
+
+>>>>> Looks like its bracketed in the code anyway... -- [[Will]]
+
+>>>> Perhaps the thing to do is to have a `clear_defines()`
+>>>> function, then merging `A` and `B` yields `(A) or (clear_defines() and (B))`
+>>>> That would deal with both the cases where `A` and `B` differently
+>>>> define `~foo` as well as with the case where `A` defines `~foo` while
+>>>> `B` uses it to refer to a literal page.
+>>>> --[[Joey]]
+
+>>>>> I don't think this will work with the new patch, and I don't think it was needed with the old one.
+>>>>> Under the old patch, pagespec_makeperl() generated a string of unevaluated, self-contained, perl
+>>>>> code.  When a new named pagespec was defined, a recursive call was made to get the perl code
+>>>>> for the pagespec, and then that code was used to add something like `$params{specFuncs}->{name} = sub {recursive code} and `
+>>>>> to the result of the calling function.  This means that at pagespec testing time, when this code is executed, the
+>>>>> specFuncs hash is built up as the pagespec is checked.  In the case of the 'or' used above, later redefinitions of
+>>>>> a named pagespec would have redefined the specFunc at the right time.  It should have just worked.  However...
+
+>>>>> Since my original patch, you started using closures for security reasons (and I can see the case for that).  Unfortunately this
+>>>>> means that the generated perl code is no longer self-contained - it needs to be evaluated in the same closure it was generated
+>>>>> so that it has access to the data array.  To make this work with the recursive call I had two options: a) make the data array a
+>>>>> reference that I pass around through the pagespec_makeperl() functions and have available when the code is finally evaluated
+>>>>> in pagespec_translate(), or b) make sure that each pagespec is evaluated in its correct closure and a perl function is returned, not a
+>>>>> string containing unevaluated perl code.
+
+>>>>> I went with option b).  I did it in such a way that the hash of specfuncs is built up at translation time, not at execution time.  This
+>>>>> means that with the new code you can call specfuncs that get defined out of order:
+
+    ~test and define(~test, blah)
+
+>>>>> but it also means that using a simple 'or' to join two pagespecs wont work.  If you do something like this:
+
+    ~test and define(~test, foo) and define(~test, baz)
+
+>>>>> then the last definition (baz) takes precedence.
+>>>>> In the process of writing this I think I've come up with a way to change this back the way it was, still using closures. -- [[Will]]
+
+>>> My [[remove-pagespec-merge|should_optimise_pagespecs]] branch has now
+>>> solved all this by deleting the offending function :-) --[[smcv]]
+
+
+
+Patch updated to use closures rather than inline generated code for named pagespecs.  Also includes some new use of ErrorReason where appropriate. -- [[Will]]
+
+> * Perl really doesn't need forward declarations, honest!
+
+>> It complained (warning, not error) when I didn't use the forward declaration. :(
+
+> * I have doubts about memoizing the anonymous sub created by
+>   `pagespec_translate`.
+
+>> This is there explicitly to make sure that runtime is polynomial and not exponential.
+
+> * Think where you wrote `+{}` you can just write `{}`
+
+>> Possibly :) -- [[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 061a1c6..1e78a63 100644
+    --- a/IkiWiki.pm
+    +++ b/IkiWiki.pm
+    @@ -1774,8 +1774,12 @@ sub pagespec_merge ($$) {
+       return "($a) or ($b)";
+     }
+     
+    -sub pagespec_translate ($) {
+    +# is perl really so dumb it requires a forward declaration for recursive calls?
+    +sub pagespec_translate ($$);
+    +
+    +sub pagespec_translate ($$) {
+       my $spec=shift;
+    +  my $specFuncsRef=shift;
+     
+       # Convert spec to perl code.
+       my $code="";
+    @@ -1789,7 +1793,9 @@ sub pagespec_translate ($) {
+               |
+                       \)              # )
+               |
+    -                  \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
+               )
+    @@ -1805,10 +1811,19 @@ sub pagespec_translate ($) {
+               elsif ($word eq "(" || $word eq ")" || $word eq "!") {
+                       $code.=' '.$word;
+               }
+    -          elsif ($word =~ /^(\w+)\((.*)\)$/) {
+    +          elsif ($word =~ /^define\(\s*(~\w+)\s*,(.*)\)$/s) {
+    +                  my $name = $1;
+    +                  my $subSpec = $2;
+    +                  my $newSpecFunc = pagespec_translate($subSpec, $specFuncsRef);
+    +                  return if $@ || ! defined $newSpecFunc;
+    +                  $specFuncsRef->{$name} = $newSpecFunc;
+    +                  push @data, qq{Created named pagespec "$name"};
+    +                  $code.="IkiWiki::SuccessReason->new(\$data[$#data])";
+    +          }
+    +          elsif ($word =~ /^(\w+)\((.*)\)$/s) {
+                       if (exists $IkiWiki::PageSpec::{"match_$1"}) {
+                               push @data, $2;
+    -                          $code.="IkiWiki::PageSpec::match_$1(\$page, \$data[$#data], \@_)";
+    +                          $code.="IkiWiki::PageSpec::match_$1(\$page, \$data[$#data], \@_, specFuncs => \$specFuncsRef)";
+                       }
+                       else {
+                               push @data, qq{unknown function in pagespec "$word"};
+    @@ -1817,7 +1832,7 @@ sub pagespec_translate ($) {
+               }
+               else {
+                       push @data, $word;
+    -                  $code.=" IkiWiki::PageSpec::match_glob(\$page, \$data[$#data], \@_)";
+    +                  $code.=" IkiWiki::PageSpec::match_glob(\$page, \$data[$#data], \@_, specFuncs => \$specFuncsRef)";
+               }
+       }
+     
+    @@ -1826,7 +1841,7 @@ sub pagespec_translate ($) {
+       }
+     
+       no warnings;
+    -  return eval 'sub { my $page=shift; '.$code.' }';
+    +  return eval 'memoize (sub { my $page=shift; '.$code.' })';
+     }
+     
+     sub pagespec_match ($$;@) {
+    @@ -1839,7 +1854,7 @@ sub pagespec_match ($$;@) {
+               unshift @params, 'location';
+       }
+     
+    -  my $sub=pagespec_translate($spec);
+    +  my $sub=pagespec_translate($spec, +{});
+       return IkiWiki::ErrorReason->new("syntax error in pagespec \"$spec\"")
+               if $@ || ! defined $sub;
+       return $sub->($page, @params);
+    @@ -1850,7 +1865,7 @@ sub pagespec_match_list ($$;@) {
+       my $spec=shift;
+       my @params=@_;
+     
+    -  my $sub=pagespec_translate($spec);
+    +  my $sub=pagespec_translate($spec, +{});
+       error "syntax error in pagespec \"$spec\""
+               if $@ || ! defined $sub;
+       
+    @@ -1872,7 +1887,7 @@ sub pagespec_match_list ($$;@) {
+     sub pagespec_valid ($) {
+       my $spec=shift;
+     
+    -  my $sub=pagespec_translate($spec);
+    +  my $sub=pagespec_translate($spec, +{});
+       return ! $@;
+     }
+     
+    @@ -1919,6 +1934,68 @@ sub new {
+     
+     package IkiWiki::PageSpec;
+     
+    +sub check_named_spec($$;@) {
+    +  my $page=shift;
+    +  my $specName=shift;
+    +  my %params=@_;
+    +
+    +  return IkiWiki::ErrorReason->new("Unable to find specFuncs in params to check_named_spec()!")
+    +          unless exists $params{specFuncs};
+    +
+    +  my $specFuncsRef=$params{specFuncs};
+    +
+    +  return IkiWiki::ErrorReason->new("Named page spec '$specName' is not valid")
+    +          unless (substr($specName, 0, 1) eq '~');
+    +
+    +  if (exists $specFuncsRef->{$specName}) {
+    +          # remove the named spec from the spec refs
+    +          # when we recurse to avoid infinite recursion
+    +          my $sub = $specFuncsRef->{$specName};
+    +          delete $specFuncsRef->{$specName};
+    +          my $result = $sub->($page, %params);
+    +          $specFuncsRef->{$specName} = $sub;
+    +          return $result;
+    +  } else {
+    +          return IkiWiki::ErrorReason->new("Page spec '$specName' does not exist");
+    +  }
+    +}
+    +
+    +sub check_named_spec_existential($$$;@) {
+    +  my $page=shift;
+    +  my $specName=shift;
+    +  my $funcref=shift;
+    +  my %params=@_;
+    +
+    +  return IkiWiki::ErrorReason->new("Unable to find specFuncs in params to check_named_spec_existential()!")
+    +                  unless exists $params{specFuncs};
+    +  my $specFuncsRef=$params{specFuncs};
+    +  
+    +  return IkiWiki::ErrorReason->new("Named page spec '$specName' is not valid")
+    +          unless (substr($specName, 0, 1) eq '~');
+    +
+    +  if (exists $specFuncsRef->{$specName}) {
+    +          # remove the named spec from the spec refs
+    +          # when we recurse to avoid infinite recursion
+    +          my $sub = $specFuncsRef->{$specName};
+    +          delete $specFuncsRef->{$specName};
+    +          
+    +          foreach my $nextpage (keys %IkiWiki::pagesources) {
+    +                  if ($sub->($nextpage, %params)) {
+    +                          my $tempResult = $funcref->($page, $nextpage, %params);
+    +                          if ($tempResult) {
+    +                                  $specFuncsRef->{$specName} = $sub;
+    +                                  return IkiWiki::SuccessReason->new("Existential check of '$specName' matches because $tempResult");
+    +                          }
+    +                  }
+    +          }
+    +          
+    +          $specFuncsRef->{$specName} = $sub;
+    +          return IkiWiki::FailReason->new("No page in spec '$specName' was successfully matched");
+    +  } else {
+    +          return IkiWiki::ErrorReason->new("Named page spec '$specName' does not exist");
+    +  }
+    +}
+    +
+     sub derel ($$) {
+       my $path=shift;
+       my $from=shift;
+    @@ -1937,6 +2014,10 @@ sub match_glob ($$;@) {
+       my $glob=shift;
+       my %params=@_;
+       
+    +  if (substr($glob, 0, 1) eq '~') {
+    +          return check_named_spec($page, $glob, %params);
+    +  }
+    +
+       $glob=derel($glob, $params{location});
+     
+       my $regexp=IkiWiki::glob2re($glob);
+    @@ -1959,8 +2040,9 @@ sub match_internal ($$;@) {
+     
+     sub match_link ($$;@) {
+       my $page=shift;
+    -  my $link=lc(shift);
+    +  my $fullLink=shift;
+       my %params=@_;
+    +  my $link=lc($fullLink);
+     
+       $link=derel($link, $params{location});
+       my $from=exists $params{location} ? $params{location} : '';
+    @@ -1975,25 +2057,37 @@ sub match_link ($$;@) {
+               }
+               else {
+                       return IkiWiki::SuccessReason->new("$page links to page $p matching $link")
+    -                          if match_glob($p, $link, %params);
+    +                          if match_glob($p, $fullLink, %params);
+                       $p=~s/^\///;
+                       $link=~s/^\///;
+                       return IkiWiki::SuccessReason->new("$page links to page $p matching $link")
+    -                          if match_glob($p, $link, %params);
+    +                          if match_glob($p, $fullLink, %params);
+               }
+       }
+       return IkiWiki::FailReason->new("$page does not link to $link");
+     }
+     
+     sub match_backlink ($$;@) {
+    -  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 ($$;@) {
+       my $page=shift;
+       my $testpage=shift;
+       my %params=@_;
+    -  
+    +
+    +  if (substr($testpage, 0, 1) eq '~') {
+    +          return check_named_spec_existential($page, $testpage, \&match_created_before, %params);
+    +  }
+    +
+       $testpage=derel($testpage, $params{location});
+     
+       if (exists $IkiWiki::pagectime{$testpage}) {
+    @@ -2014,6 +2108,10 @@ sub match_created_after ($$;@) {
+       my $testpage=shift;
+       my %params=@_;
+       
+    +  if (substr($testpage, 0, 1) eq '~') {
+    +          return check_named_spec_existential($page, $testpage, \&match_created_after, %params);
+    +  }
+    +
+       $testpage=derel($testpage, $params{location});
+     
+       if (exists $IkiWiki::pagectime{$testpage}) {