[Rd] capabilities() and non-catchable messages

[Henrik Bengtsson]

Just for the record (not a request for fix) and an ad hoc workaround if 
anyone needs it:

REASON:
Running an R script as a plugin on a remote Suse Linux 8.2 with R v2.1.0 
(2005-04-18), I have noticed that capabilities() generates (to standard 
error)

   Xlib: connection to "base:0.0" refused by server
   Xlib: Client is not authorized to connect to Server

which cannot be caught by tryCatch();

   tryCatch({
     print(capabilities());
   }, condition=function(c) {
     cat("Condition caught:\n");
     str(c);
   })

because it is not a 'condition' (error or warning).

CONTEXT:
Since source() calls capabilities("iconv") this messages always show up. 
My R plugin loads custom code using source() and since the standard 
error from the plugin is checked for messages, the host system 
interprets this as if something problematic has occured.

WORKAROUND:
The workaround that I use now is to redefine capabilities() temporarily 
(since I do not need "iconv" support):

  orgCapabilities <- base::capabilities;
  basePos <- which(search() == "package:base"));
  assign("capabilities", function(...) FALSE, pos=basePos);

  source(<my file>)

  basePos <- which(search() == "package:base"));
  assign("capabilities", orgCapabilities, pos=basePos);
  rm(orgCapabilities)

Cheers

Henrik