arrow

ARROW-13799 [R] case_when error handling is capturing strings

The approach I propose is simple - add an `abort()` if there is a `try-error` in the evaluated RHS of the `case_when()`. This error is then handled by `mutate()` which captures the call, forces a `collect()` and re-evaluates the `case_when()` call as a regular {dplyr} call.

There are a couple of potential implications for this ☝🏻 approach:
* we are working with the assumption that `case_when()` is only used inside `mutate()` and relying on `mutate()` to handle the error (via `abandon_ship()`).
* the error is not captured at `case_when()` level (which would be a bit more informative), but rather at `mutate()` level (when it becomes a bit less specific, i.e. one-step removed). The error message at `case_when()` level is not surfaced.

A follow-up question: do we want to implement a version of `case_when()` that works outside `mutate()`?

``` r
  record_batch(tbl) %>%
    mutate(
      cw = case_when(!(!(!(lgl))) ~ factor(chr),
                     TRUE ~ fct)
    ) %>%
    collect()

Warning: Expression case_when(!(!(!(lgl))) ~ factor(chr), TRUE ~ fct) not
supported in Arrow; pulling data into R
# A tibble: 10 × 8
     int   dbl  dbl2 lgl   false chr   fct   cw
   <int> <dbl> <dbl> <lgl> <lgl> <chr> <fct> <fct>
 1     1   1.1     5 TRUE  FALSE a     a     a
 2     2   2.1     5 NA    FALSE b     b     b
 3     3   3.1     5 TRUE  FALSE c     c     c
 4    NA   4.1     5 FALSE FALSE d     d     d
 5     5   5.1     5 TRUE  FALSE e     NA    NA
 6     6   6.1     5 NA    FALSE NA    NA    NA
 7     7   7.1     5 NA    FALSE g     g     g
 8     8   8.1     5 FALSE FALSE h     h     h
 9     9  NA       5 FALSE FALSE i     i     i
10    10  10.1     5 NA    FALSE j     j     j

```

<sup>Created on 2021-10-14 by the [reprex package](https://reprex.tidyverse.org) (v2.0.1)</sup>

Closes #11417 from dragosmg/ARROW-13799_case_when_error_handling

Lead-authored-by: Dragos Moldovan-Grünfeld <dragos.mold@gmail.com>
Co-authored-by: Dragoș Moldovan-Grünfeld <dragos.mold@gmail.com>
Signed-off-by: Jonathan Keane <jkeane@gmail.com>