local_options() evaluates error handler functions, fails to restore original handler

[mtmorgan]

With

library(withr)
f <- function(...) { cat("f\n"); 1 }
options(error = f)
g <- function() {
    local_options(list( error = function(...) { cat("g\n"); 2 } ))
    3
}

the evaluation of f() can be seen by the side-effect

> g()                                     # side-effect
f
[1] 3

The failure to re-establish the original handler is seen with

> options("error")                        # local option not removed
$error
(function (...) 
{
    cat("g\n")
    2
})()

The problem is in the call to set_options when returning from g()

> withr:::set_options
function (new_options) 
{
    do.call(options, as.list(new_options))
}

where do.call() evaluates as.list(new_options).

The problem came up in the context of RUnit (setting the equivalent of f() to report the traceback on error) and batchtools @mllg playing the role of g()

> head(batchtools:::execJob.Job, 3)
1 function (job)                                            
2 {                                                         
3     local_options(list(error = function(e) traceback(2L)))