[Rd] capturing multiple warnings in tryCatch()

[Fox, John]

Dear Henrik, Simon, and Adrian,

As it turns out Adrian's admisc::tryCatchWEM() *almost* does what I want, which is both to capture all messages and the result of the expression (rather than the visible representation of the result). I was easily able to modify tryCatchWEM() to return the result.

Henrik: I was aware that tryCatch() doesn't return the final result of the expression, and I was previously re-executing the expression to capture the reult, but only getting the first warning message, along with the result. 

Thanks for responding to my question and providing viable solutions,
 John

On 2021-12-02, 5:19 PM, "Henrik Bengtsson" <henrik.bengtsson using gmail.com> wrote:

    Simon's suggestion with withCallingHandlers() is the correct way.
    Also, note that if you use tryCatch() to catch warnings, you're
    *interrupting* the evaluation of the expression of interest, e.g.

    > res <- tryCatch({ message("hey"); warning("boom"); message("there"); 42 }, warning = function(w) { message("Warning caught: ", conditionMessage(w)); 3.14 })
    hey
    Warning caught: boom
    > res
    [1] 3.14

    Note how it never completes your expression.

    /Henrik

    On Thu, Dec 2, 2021 at 1:14 PM Simon Urbanek
    <simon.urbanek using r-project.org> wrote:
    >
    >
    > 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 using 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/
    > >
    > >
    > >
    > > ______________________________________________
    > > R-devel using r-project.org mailing list
    > > https://stat.ethz.ch/mailman/listinfo/r-devel
    > >
    >
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