[Rd] comment causes browser() to exit (PR#9063)

[Liaw, Andy]

If I'm not mistaken, this works as documented.  As an example (typed
directly into the Rgui console on WinXP):

R> f <- function() {
+     browser()
+     cat("I'm here!\n")
+     cat("I'm still here!\n")
+ }
R> f()
Called from: f()
Browse[1]> ## where to?
I'm here!
I'm still here!

which I think is what you saw.  However:

R> f()
Called from: f()
Browse[1]> n
debug: cat("I'm here!\n")
Browse[1]> ##
I'm here!
debug: cat("I'm still here!\n")
Browse[1]> 
I'm still here!

>From ?browser:

c
(or just return) exit the browser and continue execution at the next
statement. 
cont
synonym for c. 
n
enter the step-through debugger. This changes the meaning of c: see the
documentation for debug. 

My interpretation of this is that, if the first thing typed (or pasted) in
is something like a null statement (e.g., return, empty line, or comment),
it's the same as 'c', but if the null statement follows 'n', then it behaves
differently.

               _                         
platform       i386-pc-mingw32           
arch           i386                      
os             mingw32                   
system         i386, mingw32             
status                                   
major          2                         
minor          3.1                       
year           2006                      
month          06                        
day            01                        
svn rev        38247                     
language       R                         
version.string Version 2.3.1 (2006-06-01)


Andy


From: timh at insightful.com
> 
> I'm trying to step through some code using browser(), 
> executing one line at a time.
> Unfortunately, whenever I execute a comment line, the browser exits.
> 
> I previously reported a similar problem with blank lines.
> 
> These problems are a strong incentive to write poor code
> -- uncommented code with no blank lines to improve 
> readability -- so that I can use browser() without it exiting 
> at inconvenient times.
> 
> Additional detail:  
> (1) I'm running R inside emacs, with R in one buffer and a 
> file containing code in another, using a macro to copy and 
> paste a line at a time from the file to the R buffer.
> (2) The browser() call is inside a function.  
> Right now the lines I'm sending to the browser are not part 
> of the function, though usually they are.
> 
> 
> --please do not edit the information below--
> 
> Version:
>  platform = i386-pc-mingw32
>  arch = i386
>  os = mingw32
>  system = i386, mingw32
>  status =
>  major = 2
>  minor = 3.1
>  year = 2006
>  month = 06
>  day = 01
>  svn rev = 38247
>  language = R
>  version.string = Version 2.3.1 (2006-06-01)
> 
> Windows XP Professional (build 2600) Service Pack 2.0
> 
> Locale:
> LC_COLLATE=English_United States.1252;LC_CTYPE=English_United 
> States.1252;LC_MONETARY=English_United 
> States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252
> 
> Search Path:
>  .GlobalEnv, package:methods, package:stats, 
> package:graphics, package:grDevices, package:utils, 
> package:datasets, Autoloads, package:base
> 
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