Java client does not support the complex type

[esc-mhild]

When RConnection.eval encounters an unhandled type (e.g., complex), it prints a warning to stderr and returns null. This prevents proper error handling in Java code using the RConnection client.

The return of a null object is intended according to the documentation of the method implementation and Java code can, of course, easily check for this condition:

@return R-xpression or null if an error occured

Crucially, however, the message describing the source of the error is inaccessible to any error handling logic so that only an uninformative "Something failed" can be reported.

Moreover, writing to stderr is undesirable in Java applications where logging frameworks are the typical choice.

Replication:

In R, start a server:

library(Rserve); run.Rserve()

In Java,

RConnection c = new RConnection();

REXP r = c.eval("complex(real=1, imaginary=2)");

// prints to stderr: "unhandled type: 38"
// r == null

Many thanks!

M.

[s-u]

There are really two issues here - one is that complex type should be supported and the other is that error handling is explicitly suppressed in favor of returning null. I'll convert this issue into complex type support and raise another one.