Suppress custom dplyr warnings while allowing other warnings through

[andyteucher]

I have a function in a package that I want to call in a dplyr grouped mutate call (inside another function). The function has a tryCatch statement in it because some errors are expected, and I want to turn them into warnings. The problem is that when a function inside mutate() generates a warning, it also triggers a dplyr warning (helpfully indicating in which group the error occured) which I would like to suppress in this case. Here is a contrived toy example:

library(dplyr, warn.conflicts = FALSE)

dat <- data.frame(a = letters[1:3], b = 1:3)

user_facing_function <- function(x) {
  x %>% 
    group_by(a) %>% 
    mutate(b2 = make_b2(b))  
}

make_b2 <- function(x) {
  tryCatch(if (x > 2) stop() else x*2,
           error = function(e) {
             warning("This is the only warning I want", call. = FALSE)
             NA_real_
           })
}

user_facing_function(dat)

#> # A tibble: 3 x 3
#> # Groups:   a [3]
#>   a         b    b2
#>   <chr> <int> <dbl>
#> 1 a         1     2
#> 2 b         2     4
#> 3 c         3    NA
#> Warning message:
#>   Problem with `mutate()` input `b2`.
#> ℹ This is the only warning I want
#> ℹ Input `b2` is `make_b2(b)`.
#> ℹ The error occurred in group 3: a = "c"

<sup>Created on 2021-02-17 by the [reprex package](https://reprex.tidyverse.org) (v1.0.0)</sup>

Is there a way to turn off the dplyr-generated warning messages and just have my custom warning message?

Thanks in advance!
Andy

[andyteucher]

So far the best I have come up with is to also wrap the mutate call in tryCatch to capture and edit the warning message with regex... but that seems really inelegant.

[pieterjanvc]

Hi,

If you don't mind the "warning" message being before the output, you can just transform the warning into a message. Same colour, but no other warnings...

library(dplyr, warn.conflicts = FALSE)

dat <- data.frame(a = letters[1:3], b = 1:3)

user_facing_function <- function(x) {
  x %>% 
    group_by(a) %>% 
    mutate(b2 = make_b2(b))
}

make_b2 <- function(x) {
  tryCatch(if (x > 2) stop() else x*2,
           error = function(e) {
             message("This is the only warning I want")
             NA_real_
           })
}

user_facing_function(dat)
#> This is the only warning I want
#> # A tibble: 3 x 3
#> # Groups:   a [3]
#>   a         b    b2
#>   <chr> <int> <dbl>
#> 1 a         1     2
#> 2 b         2     4
#> 3 c         3    NA

^{Created on 2021-02-18 by the reprex package (v1.0.0)}

PJ

[andyteucher]

Thanks @pieterjanvc - I do want to keep it as a warning.

[andyteucher]

I decided to work around this by checking for the error condition and throw the warning outside of the mutate() call