Hi Duncan — Wonderful. Thank you. Bug or no bug, I think it would be
a huge improvement for user-friendliness if R printed the last line by
default *every time* a script dies. Most computer languages do so.
Should I file it as a request for improvement to the R code
development team? Maybe R can be improved at a very low cost to the
development team and a very high benefit to newbies.
Regards,
/ivo
On Sun, Jan 19, 2025 at 2:39 AM Duncan Murdoch <murdoch.dun...@gmail.com> wrote:
>
> On 2025-01-18 8:27 p.m., Ivo Welch wrote:
> > I am afraid my errors are worse! (so are my postings. I should have
> > given an example.)
> >
> > ```
> > x <- 1
> > y <- 2
> > nofunction("something stupid I am doing!")
> > z <- 4
> > ```
> >
> > and
> >
> > ```
> >> source("where-is-my-water.R")
> > Error in nofunction("something stupid I am doing!") :
> > could not find function "nofunction"
> > ```
> >
> > and no traceback is available.
>
> Okay, I see. In that case traceback() doesn't report the line, but it
> still is known internally. You can see it using the following function:
>
> showKnownLocations <- function() {
> calls <- sys.calls()
> srcrefs <- sapply(calls, function(v) if (!is.null(srcref <- attr(v,
>
> "srcref"))) {
> srcfile <- attr(srcref, "srcfile")
> paste0(basename(srcfile$filename), "#", srcref[1L])
> } else ".")
> cat("Current call stack locations:\n")
> cat(srcrefs, sep = " ")
> cat("\n")
> }
>
> I haven't done much testing on this, but I think it can be called
> explicitly from any location if you want to know how you got there, or
> you can set it as the error handler using
>
> options(error = showKnownLocations)
>
> For example, try this script:
>
> options(error = showKnownLocations)
> f <- function() showKnownLocations()
> x <- 1
> f()
> y <- 2
> nofunction("something stupid I am doing!")
> z <- 4
>
> I see this output from source("test.R"):
>
> > source("test.R")
> Current call stack locations:
> . . . . test.R#4 test.R#2
> Error in nofunction("something stupid I am doing!") :
> could not find function "nofunction"
> Current call stack locations:
> . . . . test.R#6
>
> The first report is from the explicit call in f() on line 2 that was
> invoked on line 4, and the second report happens during error handling.
>
> I supppose the fact that traceback() isn't showing you the line 6
> location could be considered a bug.
>
> Duncan Murdoch
>
>
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