inline: Run format hook first

inline has a format hook that is an optimisation hack. Until this hook
runs, the inlined content is not present on the page. This can prevent
other format hooks, that process that content, from acting on inlined
content. In bug ##509710, we discovered this happened commonly for the
embed plugin, but it could in theory happen for many other plugins (color,
cutpaste, etc) that use format to fill in special html after sanitization.

The ordering was essentially random (hash key order). That's kinda a good
thing, because hooks should be independent of other hooks and able to run
in any order. But for things like inline, that just doesn't work.

To fix the immediate problem, let's make hooks able to be registered as
running "first". There was already the ability to make them run "last".

Now, this simple first/middle/last ordering is obviously not going to work
if a lot of things need to run first, or last, since then we'll be back to
being unable to specify ordering inside those sets. But before worrying about
that too much, and considering dependency ordering, etc, observe how few
plugins use last ordering: Exactly one needs it. And, so far, exactly one
needs first ordering. So for now, KISS.

Another implementation note: I could have sorted the plugins with
first/last/middle as the primary key, and plugin name secondary, to get a
guaranteed stable order. Instead, I chose to preserve hash order. Two
opposing things pulled me toward that decision:

1. Since has order is randomish, it will ensure that no accidental
   ordering assumptions are made.
2. Assume for a minute that ordering matters a lot more than expected.
   Drastically changing the order a particular configuration uses could
   result in a lot of subtle bugs cropping up. (I hope this assumption is
   false, partly due to #1, but can't rule it out.)

4 files changed, 16 insertions, 10 deletions

diff --git a/IkiWiki.pm b/IkiWiki.pm
index cc1e89acc..54e00ec7b 100644
--- a/IkiWiki.pm
+++ b/IkiWiki.pm
@@ -1536,15 +1536,19 @@ sub run_hooks ($$) {
 	my $sub=shift;
 
 	if (exists $hooks{$type}) {
-		my @deferred;
+		my (@first, @middle, @last);
 		foreach my $id (keys %{$hooks{$type}}) {
-			if ($hooks{$type}{$id}{last}) {
-				push @deferred, $id;
-				next;
+			if ($hooks{$type}{$id}{first}) {
+				push @first, $id;
+			}
+			elsif ($hooks{$type}{$id}{last}) {
+				push @last, $id;
+			}
+			else {
+				push @middle, $id;
 			}
-			$sub->($hooks{$type}{$id}{call});
 		}
-		foreach my $id (@deferred) {
+		foreach my $id (@first, @middle, @last) {
 			$sub->($hooks{$type}{$id}{call});
 		}
 	}
diff --git a/IkiWiki/Plugin/inline.pm b/IkiWiki/Plugin/inline.pm
index 8490b455f..58da0beb8 100644
--- a/IkiWiki/Plugin/inline.pm
+++ b/IkiWiki/Plugin/inline.pm
@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+!/usr/bin/perl
 # Page inlining and blogging.
 package IkiWiki::Plugin::inline;
 
@@ -22,7 +22,7 @@ sub import {
 		call => \&IkiWiki::preprocess_inline);
 	hook(type => "pagetemplate", id => "inline",
 		call => \&IkiWiki::pagetemplate_inline);
-	hook(type => "format", id => "inline", call => \&format);
+	hook(type => "format", id => "inline", call => \&format, first => 1);
 	# Hook to change to do pinging since it's called late.
 	# This ensures each page only pings once and prevents slow
 	# pings interrupting page builds.
diff --git a/debian/changelog b/debian/changelog
index 96a70fcc9..0fa6590f0 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -5,6 +5,8 @@ ikiwiki (2.72) UNRELEASED; urgency=low
   * camelcase: Add camelcase_ignore setting.
   * googlecalendar: Add runtime deprecation warning.
   * comments: Deal with users entering unqualified or partial urls.
+  * inline: Run format hook first, to ensure other format hooks can affect
+    inlined content.  Closes: #509710
 
  -- Joey Hess <joeyh@debian.org>  Mon, 22 Dec 2008 19:02:16 -0500
 
diff --git a/doc/plugins/write.mdwn b/doc/plugins/write.mdwn
index b6fa96f91..9b5cf27f7 100644
--- a/doc/plugins/write.mdwn
+++ b/doc/plugins/write.mdwn
@@ -55,8 +55,8 @@ plugin, and a "call" parameter, which tells what function to call for the
 hook.
 
 An optional "last" parameter, if set to a true value, makes the hook run
-after all other hooks of its type. Useful if the hook depends on some other
-hook being run first.
+after all other hooks of its type, and an optional "first" parameter makes
+it run first. Useful if the hook depends on some other hook being run first.
 
 ## Types of hooks