X-Git-Url: http://git.vanrenterghem.biz/git.ikiwiki.info.git/blobdiff_plain/ba480baa9ec9e2d5d04c6eb06fd3ab4dafd60794..d3008b626ea6130d3b75662725f6f2c412fc71ea:/doc/plugins/write/external.mdwn?ds=sidebyside

diff --git a/doc/plugins/write/external.mdwn b/doc/plugins/write/external.mdwn
index 2ee841e61..bda34b771 100644
--- a/doc/plugins/write/external.mdwn
+++ b/doc/plugins/write/external.mdwn
@@ -53,8 +53,8 @@ it, external plugins can use the `getstate` and `setstate` RPCs. To access
 stored state, call `getstate("page", "id", "key")`, and to store state,
 call `setstate("page", "id", "key", "value")`.
 
-To access ikiwiki's ARGV, call `getargv()`. To change its ARGV, call
-`setargv(value)`.
+To access ikiwiki's ARGV array, call `getargv()`. To change its ARGV, call
+`setargv(array)`.
 
 ## Notes on function parameters
 
@@ -79,6 +79,19 @@ Other languages might not find it so easy. If not, it might be a good idea
 to convert these named parameters into something more natural for the
 language as part of their XML RPC interface.
 
+## undef
+
+XML RPC has a limitation that it does not have a way to pass
+undef/NULL/None. There is an extension to the protocol that supports this,
+but it is not yet available in the [[cpan XML::RPC]] library used by
+ikiwiki.
+
+Until the extension is available, ikiwiki allows undef to be communicated
+over XML RPC by passing a sentinal value, a hash with a single key "null"
+with a value of an empty string. External plugins that need to communicate
+null values to or from ikiwiki will have to translate between undef and
+the sentinal.
+
 ## Function injection
 
 Some parts of ikiwiki are extensible by adding functions. For example, the