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.duncan at 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 > >
iuke-tier@ey m@iii@g oii uiow@@edu
2025-Jan-19 16:46 UTC
[R] [External] Re: Parser For Line Number Tracing
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.duncan at 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 >> >> > > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide r-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. >-- Luke Tierney Ralph E. Wareham Professor of Mathematical Sciences University of Iowa Phone: 319-335-3386 Department of Statistics and Fax: 319-335-3017 Actuarial Science 241 Schaeffer Hall email: luke-tierney at uiowa.edu Iowa City, IA 52242 WWW: stat.uiowa.edu
I think I considered doing that many years ago, but one or more of the following stopped me: - It will mess up old test scripts that are checking for the old format error messages. - Some errors are due to a severe lack of resources (e.g. full stack, out of some other kind of memory, etc.) and error reporting for those has to be done very carefully so as not to crash R. - The error handling code is pretty hairy, and I was somewhat afraid of touching it. On the other hand, it's probably not too hard to write a package that includes something like my suggestion below and perhaps some other changes specifically directed at newbies. So I might suggest looking for that package and writing it if it hasn't already been written. There are various coding parties each year that might want to take it on if you don't have time to do so. I've cc'd Heather Turner, who has been involved in organizing them recently; I don't know if she's still doing that. Duncan On 2025-01-19 10:24 a.m., 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. > > Regards, > > /ivo > > On Sun, Jan 19, 2025 at 2:39?AM Duncan Murdoch <murdoch.duncan at 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 >> >>