Question

When I use tryCatch, I can define an error handler and use conditionCall to determine the call that caused the error. For instance,

tryCatch(
    eval(parse(text="prnit('Hello')")),
    error=function(e) {
      cl <- conditionCall(e)
      #...
    })

Can I get to the bad call on the R prompt? Until now, I found only this solution:

> err_hdl  <- function() {
    file1 <- tempfile("Rrawhist")
    savehistory(file1)
    rawhist <- readLines(file1)
    unlink(file1)

    cat("Error : ", tail(rawhist,1), "\n")
    return(TRUE)    
}
> options(error=err_hdl)
> prnit("Hello")

but I believe there must be a more straightforward way..

Any hint appreciated!

I put out a bounty. The first answer that implements the behaviour of the err_hdl function above without file I/O that is platform independent will be accepted.

Edit — the code above seems only to work on windows. I am looking for the input that raised the error.

Answer 1

It looks like dump.frames can be told not to dump to a file but rather to an object in the .GlobalEnv. However, I haven’t tested it on anything but a Mac. Would the following help?

err_hdl2 <- function() {
  dump.frames("theErr", to.file = FALSE)
  cat("What happened?\n", attr(theErr,"error.message"), "\nOh.\n")
}
options(error = err_hdl2)

> prnit(dt)
Error: could not find function "prnit"
What happened?
 Error: could not find function "prnit"

Oh.

There might be a drawback to creating the object theErr in the global environment, I suppose.

> theErr
$`function () 
{
    dump.frames("theErr", to.file = FALSE)
    cat("What`
<environment: 0x1030fe140>

attr(,"error.message")
[1] "Error: could not find function \"prnit\"\n"
attr(,"class")
[1] "dump.frames"