how to active R taskcallback after error

Question

i would like to know how to have a callback after an error.

I tried this, but it doesn't work with error :

addTaskCallback(
  function(expr, value, ok, visible) {
    print("ok")
    TRUE
  }
)
getTaskCallbackNames()

print(1) #ok 
ls() #ok
dont_exist() # the taskcallback isn't activated

EDIT:

GOT IT!

if (!require(devtools)){install.packages("devtools")}
devtools::install_github("ThinkRstat/fcuk")
library(fcuk)
sl()
iri
view
mea

Answer 1

R provides some method to add handlers for errors and warnings. You can use something like

.Internal(.addCondHands("error", 
                        list(error = function(e) {print("ok")}), 
                        .GlobalEnv, NULL, TRUE))

to add a callback function for error. I didn't find much documentation for this, but you can see the source for withCallingHandlers and tryCatch to see how to use it.

Edit:

And I also find one method to have a callback after an error, but not in a pure R way. It relies on Rstudio's error callback mechanism:

If you use Rstudio, you will find a global option "error" which Rstudio uses as an error callback function. You can see it by: getOption("error") and change it like this:

f <- function(){
    print("ok")
}

options(error = f)

And if you want to collect the most recent error message, you can use geterrmessage(), which is built into R.