Is there a way to debug an R script run from the command line with Rscript.exe - r

Question

Is it possible to debug an R source file which is executed with Rscript.exe?
> Rscript.exe mysource.R various parameters
Ideally, I would like to be able to set a break-point somewhere in the mysource.R file in RStudio.
Is entering the R debugger directly at the command line possible for instance by adding some debug directive to the source file?
Maybe sourcing the file from R would work? How? How do I pass the command line arguments "various parameters" so that commandArgs() returns the correct values?
The mysource.R could look as follows (in practice it is much more complicated).
#!/usr/bin/Rscript
args <- commandArgs(trailingOnly=TRUE)
print(args)

Answer 1

As far as debugging from console is concerned there are few questions related to it without an answer.
Is there a way to debug an RScript call in RStudio? and Rscript debug using command line
So, I am not sure if something has changed and if it is now possible.
However, we can debug from sourcing the file by using a hack. You could add browser() in the file wherever you want to debug. Consider your main file as :
main.R
args <- commandArgs(trailingOnly=TRUE)
browser()
print(args)
Now, we can override the commandArgs function and pass whatever arguments we want to pass which will be passed when you source the file.
calling_file.R
commandArgs <- function(...) list(7:9, letters[1:3])
source("main.R")
After running the source command, you could debug from there
Called from: eval(ei, envir)
#Browse[1]> args
#[[1]]
#[1] 7 8 9
#[[2]]
#[1] "a" "b" "c"

Answer 2

There's no native way to debug Rscript in the command line, but you can use a kind of hacky workaround I whipped up with readLines and eval.
ipdb.r <- function(){
input <- ""
while(!input %in% c("c","cont","continue"))
{
cat("ipdb.r>")
# stdin connection to work outside interactive session
input <- readLines("stdin",n=1)
if(!input %in% c("c","cont","continue","exit"))
{
# parent.frame() runs command outside function environment
print(eval(parse(text=input),parent.frame()))
}else if(input=="exit")
{
stop("Exiting from ipdb.r...")
}
}
}
Example usage in an R file to be called with Rscript:
ipdbrtest.R
a <- 3
print(a)
ipdb.r()
print(a)
Command line:
$ Rscript ipdbrtest.R
[1] 3
ipdb.r>a+3
[1] 6
ipdb.r>a+4
[1] 7
ipdb.r>a <- 4
[1] 4
ipdb.r>c
[1] 4
If you're considering using R instead of Rscript, you could pass it environment variables and retrieve them with Sys.getenv().