Question

When a call exists of multiple lines, a potential error only includes the first line of match.call() resulting in some lost information and an incomplete sentence. A simple example:

#proper error message:
runif(n=1, k=5)

#incomplete error message:
runif(n=1, k={5})

What would be a way to get R to include the full call to the error message (maybe by collapsing the multiple lines or so)? I am mostly interested in using this in a tryCatch setting.

Answer 1

I had a go at investigating the error object in a tryCatch setting via:

tryCatch( runif(n=1,k={5}),
          error = function(e) recover() )

And then selected the 4th environment (value[[3]](cond)) to examine e.

I noticed that e$call was:

Browse[1]> e$call
runif(n = 1, k = {
    5
})

So it seems that the error message just uses that first line.

You can collapse all the lines together with:

Browse[1]> paste(deparse(e$call),collapse='')
[1] "runif(n = 1, k = {    5})"

So you could try something like:

tryCatch( runif(n=1,k={5}),
          error = function(e) {
            cat(sprintf('Error in %s: %s\n',
                 paste(deparse(e$call),collapse=''),
                 e$message))
          } )

But this doesn’t fix up the error message itself, just the call leading up to it:

Error in runif(n = 1, k = { 5}): unused argument(s) (k = {

So the ‘Error in xxx’ is complete, but the ‘unused argument(s) xxx’ is still not. It’s a start, but not all the way there.

I’m not sure how to improve on this (and am also interested to know if it’s possible).