"could not find function" only when in the R debugger

Question

I've been running into this from time to time but for the first time I have simple reproducible example. The fact that the example involves lubridate is, I believe, coincidental. In R --vanilla session

library(lubridate)
ymd("2001-02-02")
# [1] "2001-02-02 UTC"
# so far so good
debug(ymd)
ymd("2001-02-02")
# debugging in: ymd("2001-02-02")
# Error in ymd("2001-02-02") : could not find function ".parse_xxx"

There is nothing wrong with ymd, I was trying to learn some things. But when you are actually debugging and this happens, it's very annoying. Debugger bug or am I missing something?

Version info

    > R.version
               _                           
platform       x86_64-apple-darwin13.4.0   
arch           x86_64                      
os             darwin13.4.0                
system         x86_64, darwin13.4.0        
status                                     
major          3                           
minor          1.2                         
year           2014                        
month          10                          
day            31                          
svn rev        66913                       
language       R                           
version.string R version 3.1.2 (2014-10-31)
nickname       Pumpkin Helmet  

And session infor per @Joshua Urlich comment

  > sessionInfo()
R version 3.1.2 (2014-10-31)
Platform: x86_64-apple-darwin13.4.0 (64-bit)

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] lubridate_1.3.3

loaded via a namespace (and not attached):
[1] digest_0.6.4  memoise_0.2.1 plyr_1.8.1    Rcpp_0.11.3   stringr_0.6.2

Thanks

Answer 1

Looks like it might have to do with the functions not being defined using {}. The current implementation is:

ymd <- function(..., quiet = FALSE, tz = "UTC", locale = Sys.getlocale("LC_TIME"),  truncated = 0)
  .parse_xxx(..., orders = "ymd", quiet = quiet, tz = tz, locale = locale,  truncated = truncated)

Your debug attempt works if I unpack the source, and change the implementation to:

ymd <- function(..., quiet = FALSE, tz = "UTC", locale = Sys.getlocale("LC_TIME"),  truncated = 0)
{  .parse_xxx(..., orders = "ymd", quiet = quiet, tz = tz, locale = locale,  truncated = truncated)}

I was able to replicate the issue before making the above change. After making it, I get:

> require(lubridate); debug(ymd); ymd("2015-01-01")
Loading required package: lubridate
debugging in: ymd("2015-01-01")
debug: {
    .parse_xxx(..., orders = "ymd", quiet = quiet, tz = tz, locale = locale, 
        truncated = truncated)
}
Browse[2]> 
debug: .parse_xxx(..., orders = "ymd", quiet = quiet, tz = tz, locale = locale, 
    truncated = truncated)
Browse[2]> 
exiting from: ymd("2015-01-01")
[1] "2015-01-01 UTC"

Answer 2

Not a solution or explanation but a potential work around:

trace(ymd, browser)

Then:

> ymd("2001-02-02")
Tracing ymd("2001-02-02") on entry 
Called from: eval(expr, envir, enclos)
Browse[1]> n
debug: .parse_xxx(..., orders = "ymd", quiet = quiet, tz = tz, locale = locale, 
    truncated = truncated)
Browse[2]> 

I am able to recreate your error on Win7 R3.1.2 / RStudio. I was hoping to recreate the problem with trace to try to poke around, but any trace of the function destroys the problem...