[Rd] capturing multiple warnings in tryCatch()

[Adrian Dușa]

Dear John,

The logical argument capture is already in production use by other
packages, but I think this is easily solved by:

if (!is.null(output$value) & output$visible) {
    if (capture) {
        toreturn$output <- capture.output(output$value)
    }
    toreturn$value <- output$value
}

so that value is always part of the return list, if visible.

This is a very good suggestion, and I've already incorporated it into this
function.

All the best,
Adrian

On Fri, 3 Dec 2021 at 21:42, Fox, John <jfox using mcmaster.ca> wrote:

> Dear Adrian,
>
> Here's my slightly modified version of your function, which serves my
> purpose:
>
> ------- snip -------
>
> tryCatchWEM <- function (expr, capture = TRUE) {
>     toreturn <- list()
>     output <- withVisible(withCallingHandlers(
>         tryCatch(expr,
>                  error = function(e) {
>                      toreturn$error <<- e$message
>                      NULL
>                  }), warning = function(w) {
>                      toreturn$warning <<- c(toreturn$warning, w$message)
>                      invokeRestart("muffleWarning")
>                  }, message = function(m) {
>                      toreturn$message <<- paste(toreturn$message,
> m$message,
>                                                 sep = "")
>                      invokeRestart("muffleMessage")
>                  }))
>     if (capture & output$visible) {
>         if (!is.null(output$value)) {
>             toreturn$result <- output$value
>         }
>     }
>     if (length(toreturn) > 0) {
>         return(toreturn)
>     }
> }
>
> ------- snip -------
>
> The two small modifications are to change the default of capture to TRUE
> and to return output$value rather than capture.output(output$value). So a
> suggestion would be to modify the capture argument to, say, capture=c("no",
> "output", "value") and then something like
>
>         . . .
>         capture <- match.arg(capture)
>         . . .
>         if (capture == "output"){
>         toreturn$output <- capture.output(output$value)
>         } else if (capture == "value"){
>                 toreturn$value <- output$value
>         }
>         . . .
>
> Best,
>  John
>
> On 2021-12-03, 1:56 PM, "R-devel on behalf of Adrian Dușa" <
> r-devel-bounces using r-project.org on behalf of dusa.adrian using gmail.com> wrote:
>
>     On Fri, 3 Dec 2021 at 00:37, Fox, John <jfox using mcmaster.ca> wrote:
>
>     > 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.
>     >
>
>     Glad it helps.
>     I would be happy to improve the function, should you send a reprex
> with the
>     desired final result.
>
>     Best wishes,
>     Adrian
>
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>
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