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rcran

overriding R's incomplete error messages

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.

Solution

  • 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).