capturing multiple warnings in tryCatch()

res <- tryCatch({ message("hey"); warning("boom"); message("there"); 42 }, warning = function(w) { message("Warning caught: ", conditionMessage(w)); 3.14 })

res

Adapted from demo(error.catching):

W=list()
withCallingHandlers(foo(), warning=function(w) { W <<- c(W, list(w)); invokeRestart("muffleWarning") })
str(W)

List of 2
 $ :List of 2
  ..$ message: chr "warning 1"
  ..$ call   : language foo()
  ..- attr(*, "class")= chr [1:3] "simpleWarning" "warning" "condition"
 $ :List of 2
  ..$ message: chr "warning 2"
  ..$ call   : language foo()
  ..- attr(*, "class")= chr [1:3] "simpleWarning" "warning" "condition"

Cheers,
Simon

On Dec 3, 2021, at 10:02 AM, Fox, John <jfox at mcmaster.ca> wrote:

Dear R-devel list members,

Is it possible to capture more than one warning message using tryCatch()? The answer may be in ?conditions, but, if it is, I can't locate it.

For example, in the following only the first warning message is captured and reported:

foo <- function(){

+   warning("warning 1")
+   warning("warning 2")
+ }

foo()

Warning messages:
1: In foo() : warning 1
2: In foo() : warning 2

bar <- function(){

+   tryCatch(foo(), warning=function(w) print(w))
+ }

bar()

<simpleWarning in foo(): warning 1>

Is there a way to capture "warning 2" as well?

Any help would be appreciated.

John

--
John Fox, Professor Emeritus
McMaster University
Hamilton, Ontario, Canada
Web: http://socserv.mcmaster.ca/jfox/