trycatch not working in map()

[plukethep]

The following code works as expected:

    map(c(1,2,3),
        function(x){
          record <-tryCatch({
            completed <- read_csv("http://example/com/madeup.csv")
            return(completed)
          },
          error=function(cond) {
            message("CAUGHT", cond)
            return(0)
          })
        })

But if I add another message command to the error part of trycatch it errors out

    map(c(1,2,3),
        function(x){
          record <-tryCatch({
            completed <- read_csv("http://example/com/madeup.csv")
            return(completed)
          },
          error=function(cond) {
            message("CAUGHT")
            message(cond)
            return(0)
          })
        })

    CAUGHT
    Error in `map()`:
    ℹ In index: 1.
    Caused by error in `open.connection()`:
    ! Could not resolve host: example
    Run `rlang::last_error()` to see where the error occurred.
    Called from: signal_abort(cnd, .file)

Putting this trycatch in a for loop works fine:

    for(x in c(1,2,3)){
        record <-tryCatch({
            completed <- read_csv("http://example/com/madeup.csv")
            return(completed)
          },
          error=function(cond) {
            message("CAUGHT")
            message(cond)
            return(0)
          })
    }

See discussion here, which suggest's that the casting for the message(cond) is at fault

purrr 1.0.0

[hadley]

Could you please rework your reproducible example to use the reprex package ? That makes it easier to see both the input and the output, formatted in such a way that I can easily re-run in a local session.

[plukethep]

library(tidyverse)

map(c(1,2,3),
    function(x){
      record <-tryCatch({
        completed <- read_csv("http://example/com/madeup.csv")
        return(completed)
      },
      error=function(cond) {
        message("CAUGHT")
        message(cond)
        return(0)
      })
    })
#> CAUGHT
#> Error in `map()`:
#> ℹ In index: 1.
#> Caused by error in `open.connection()`:
#> ! Could not resolve host: example

#> Backtrace:
#>      ▆
#>   1. ├─purrr::map(...)
#>   2. │ └─purrr:::map_("list", .x, .f, ..., .progress = .progress)
#>   3. │   ├─purrr:::with_indexed_errors(...)
#>   4. │   │ └─base::withCallingHandlers(...)
#>   5. │   └─global .f(.x[[i]], ...)
#>   6. │     └─base::tryCatch(...)
#>   7. │       └─base (local) tryCatchList(expr, classes, parentenv, handlers)
#>   8. │         └─base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
#>   9. │           └─value[[3L]](cond)
#>  10. │             └─base::message(cond)
#>  11. │               ├─base::withRestarts(...)
#>  12. │               │ └─base (local) withOneRestart(expr, restarts[[1L]])
#>  13. │               │   └─base (local) doWithOneRestart(return(expr), restart)
#>  14. │               └─base::signalCondition(cond)
#>  15. └─purrr (local) `<fn>`(`<smplErrr>`)
#>  16.   └─cli::cli_abort(c(i = "In index: {i}."), parent = cnd, call = error_call)
#>  17.     └─rlang::abort(...)

^{Created on 2023-01-18 with reprex v2.0.2}

[hadley]

I simplified your example a little bit, but I don't see the problem. It looks like f() behaves the same way inside and outside of map():

library(purrr)

f <- function(i) {
  tryCatch(
    {
      stop("error")
    },
    error = function(cond) {
      message(cond)
      return(0)
    }
  )
}
f()
#> Error in doTryCatch(return(expr), name, parentenv, handler): error

map(c(1,2,3), f)
#> Error in `map()`:
#> ℹ In index: 1.
#> Caused by error in `doTryCatch()`:
#> ! error

^{Created on 2023-01-18 with reprex v2.0.2}

This is generally what I'd expect based on my understanding of message(): you're passing an error condition to message which will resignal it, causing the error to be rethrown.

What are you trying to do?

[plukethep]

I'm trying to catch and display the error within a map function, I believe that it used to display message absolutely fine, but has stopped since I upgraded to purrr 1.0.0 I'm still getting for loops and the f() function displaying the error message without complaint, and the for loop finishes, whilst the map function dies when it meets the error, see below

library(purrr)

f <- function(){
  tryCatch({
    stop("error")
  },
  error=function(cond) {
    message(cond)
  })
}

for(x in c(1)){
  f()
}
#> Error in doTryCatch(return(expr), name, parentenv, handler): error

f()
#> Error in doTryCatch(return(expr), name, parentenv, handler): error

map(c(1),function(x){
  f()
})
#> Error in `map()`:
#> ℹ In index: 1.
#> Caused by error in `doTryCatch()`:
#> ! error

#> Backtrace:
#>      ▆
#>   1. ├─purrr::map(...)
#>   2. │ └─purrr:::map_("list", .x, .f, ..., .progress = .progress)
#>   3. │   ├─purrr:::with_indexed_errors(...)
#>   4. │   │ └─base::withCallingHandlers(...)
#>   5. │   └─global .f(.x[[i]], ...)
#>   6. │     └─global f()
#>   7. │       └─base::tryCatch(...)
#>   8. │         └─base (local) tryCatchList(expr, classes, parentenv, handlers)
#>   9. │           └─base (local) tryCatchOne(expr, names, parentenv, handlers[[1L]])
#>  10. │             └─value[[3L]](cond)
#>  11. │               └─base::message(cond)
#>  12. │                 ├─base::withRestarts(...)
#>  13. │                 │ └─base (local) withOneRestart(expr, restarts[[1L]])
#>  14. │                 │   └─base (local) doWithOneRestart(return(expr), restart)
#>  15. │                 └─base::signalCondition(cond)
#>  16. └─purrr (local) `<fn>`(`<smplErrr>`)
#>  17.   └─cli::cli_abort(c(i = "In index: {i}."), parent = cnd, call = error_call)
#>  18.     └─rlang::abort(...)

^{Created on 2023-01-18 with reprex v2.0.2}

[hadley]

It doesn't look like the for loop is working:

library(purrr)

f <- function(){
  tryCatch({
    stop("error")
  },
  error=function(cond) {
    message(cond)
  })
}

for(x in 1:10){
  f()
  print(x)
}
#> Error in doTryCatch(return(expr), name, parentenv, handler): error

^{Created on 2023-01-18 with reprex v2.0.2}

I'd suggest going back to the drawing board and creating a reprex that actually illustrates the problem. I'm not seeing any evidence that this is related to purrr.