Missing variable "role" in "pg_settings"?

Hi

The per-session variable "role" is not shown when
doing "select pg_settings". It is, however, possible
to set it using "set role ...", and to query it using
"show role". Is this per design, or is this a bug.

I stumbled over this issue, because pgadmin3 lets
you do "alter user set <variable> <value" using the gui
(You can specify per-user variables in a tab in the
user dialog). But pgadmin only lets one choose variables
that are included in pg_settings, so one cannot archive
the effect of "alter user
<user> set role <role>" (i.e change the initial role of a user)
using the gui. In case omiting role from pg_settings is per design,
how could pgadmin find _all_ variables that can be set per user?

greetings, Florian Pflug