Allow external plugins to return no value

Instead of using the XML-RPC v2 extension <nil/>, which Perl's
XML::RPC::Parser does not (yet) support (Joey's patch is pending), we
agreed on a sentinel: {'null':''}, that is, a hash with a single key
"null" pointing to the empty string.

The Python proxy automatically converts None appropriately and raises an
exception if a hook function should, by weird coincidence, attempt to
return {'null':''}.

Signed-off-by: martin f. krafft <madduck@madduck.net>

1 files changed, 24 insertions, 1 deletions

diff --git a/IkiWiki/Plugin/external.pm b/IkiWiki/Plugin/external.pm
index 4c2e5d2fe..204442c1e 100644
--- a/IkiWiki/Plugin/external.pm
+++ b/IkiWiki/Plugin/external.pm
@@ -68,7 +68,22 @@ sub rpc_call ($$;@) { #{{{
 					return @{$value->value};
 				}
 				elsif ($value->isa('RPC::XML::struct')) {
-					return %{$value->value};
+					my %hash=%{$value->value};
+
+					# XML-RPC v1 does not allow for
+					# nil/null/None/undef values to be
+					# transmitted, so until
+					# XML::RPC::Parser honours v2
+					# (<nil/>), external plugins send
+					# a hash with one key "null" pointing
+					# to an empty string.
+					if (exists $hash{null} &&
+					    $hash{null} eq "" &&
+					    int(keys(%hash)) == 1) {
+						return undef;
+					}
+
+					return %hash;
 				}
 				else {
 					return $value->value;
@@ -92,6 +107,14 @@ sub rpc_call ($$;@) { #{{{
 				error("XML RPC call error, unknown function: $name");
 			}
 
+			# XML-RPC v1 does not allow for nil/null/None/undef
+			# values to be transmitted, so until XML::RPC::Parser
+			# honours v2 (<nil/>), send a hash with one key "null"
+			# pointing to an empty string.
+			if (! defined $ret) {
+				$ret={"null" => ""};
+			}
+
 			my $string=eval { RPC::XML::response->new($ret)->as_string };
 			if ($@ && ref $ret) {
 				# One common reason for serialisation to