Thanks for pointing out the options. Using
options(show.error.locations = TRUE)
works on Ivo's example, but it doesn't show a location if the error
happens in a function that doesn't have srcrefs, because the known
location isn't on the top of the stack.
Perhaps TRUE (and maybe "top"?) should look back through the stack until
it finds a known location, and report that, or another option (e.g.
"highest"?) could be added to do that.
And still I think traceback() should show the top call in Ivo's example.
Duncan
On 2025-01-19 11:46 a.m., luke-tier...@uiowa.edu wrote:
On Sun, 19 Jan 2025, Ivo Welch wrote:
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.
No. There are already many ways to influence the way the default error
handler prints information about errors, mstly via options(). In
particular you may want to look at entries in ?options for
show.error.locations
showErrorCalls
showWarningCalls
and adjust your options settings accordingly.
Best,
luke
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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