Column classes don't survive dplyr::bind_rows (or joins?)

[jimjam-slam]

Some workflows I'm testing that involve using dplyr::bind_rows() on data frames that have collateral columns cause them to lose their formatting:

library(tidyverse)
library(collateral)

test =
  # tidy up and trim down for the example
  mtcars %>%
  rownames_to_column(var = "car") %>%
  as_tibble() %>%
  select(car, cyl, disp, wt) %>%
  # spike some rows in cyl == 4 to make them fail
  mutate(wt = dplyr::case_when(
    wt < 2 ~ -wt,
    TRUE ~ wt)) %>%
  # nest and do some operations quietly()
  nest(-cyl) %>%
  mutate(qlog = map_quietly(data, ~ log(.$wt)))

# now slice them up...
test1 = test %>% slice(1)
test2 = test %>% slice(2)
test3 = test %>% slice(3)

# ... and combine them. problem!
test_rejoined = bind_rows(test1, test2, test3)
#> Warning in bind_rows_(x, .id): Vectorizing 'quietly_mapped' elements may
#> not preserve their attributes

#> Warning in bind_rows_(x, .id): Vectorizing 'quietly_mapped' elements may
#> not preserve their attributes

#> Warning in bind_rows_(x, .id): Vectorizing 'quietly_mapped' elements may
#> not preserve their attributes
test_rejoined
#> # A tibble: 3 x 3
#>     cyl data              qlog      
#>   <dbl> <list>            <list>    
#> 1     6 <tibble [7 x 3]>  <list [4]>
#> 2     4 <tibble [11 x 3]> <list [4]>
#> 3     8 <tibble [14 x 3]> <list [4]>
class(test_rejoined$qlog)
#> [1] "list"

^{Created on 2019-07-09 by the reprex package (v0.3.0)}

This took me by surprise a little, as my understanding is that classes are supposed to be exempt from attributes getting wiped when a vector is modified. So I'm not 100% sure what's happening, but it may be that I need to handle collateral lists getting concatenated or subsetted a little more explicitly.

R/format.r has some extra S3 methods that I mostly added because I was trying to follow along with the pillar documentation, but I wonder if—for example—these two might deserve some more attention:

#' @rdname collateral_extras
#' @export
c.safely_mapped <- function(x, ...) {
  as_safely_mapped(NextMethod())
}

#' @rdname collateral_extras
#' @export
`[.safely_mapped` <- function(x, i) {
  as_safely_mapped(NextMethod())
}

Originally posted by @Rensa in #9 (comment)

[jimjam-slam]

This may also be related to tidyverse/dplyr#2457. I'm not sure if simply implementing c and [ properly would fix the problem, though.