hoist doesn't handle duplicate names well

[mgirlich]

hoist() simply overwrites existing columns and doesn't check that the names of the ... argument are unique:

library(tidyr)
df <- tibble(
  character = c("Toothless", "Dory"),
  metadata = list(
    list(
      species = "dragon",
      color = "black",
      films = c(
        "How to Train Your Dragon",
        "How to Train Your Dragon 2",
        "How to Train Your Dragon: The Hidden World"
       )
    ),
    list(
      species = "blue tang",
      color = "blue",
      films = c("Finding Nemo", "Finding Dory")
    )
  )
)

# doesn't care about duplicate name
hoist(.data = df,
  .col = metadata,
  film = list("films", 1L),
  film = list("films", 3L)
)
#> # A tibble: 2 x 4
#>   character film                 film                             metadata      
#>   <chr>     <chr>                <chr>                            <list>        
#> 1 Toothless How to Train Your D… How to Train Your Dragon: The H… <named list […
#> 2 Dory      Finding Nemo         <NA>                             <named list […

# overwrite existing column
hoist(.data = df,
  .col = metadata,
  character = list("films", 2L)
)
#> # A tibble: 2 x 2
#>   metadata         character                 
#>   <list>           <chr>                     
#> 1 <named list [3]> How to Train Your Dragon 2
#> 2 <named list [3]> Finding Dory

^{Created on 2019-12-13 by the reprex package (v0.3.0)}

[hadley]

Yes, hoist() uses the same principle of mutate(). This could be documented better.

[mgirlich]

What about the first case with duplicate names in the dots?

# doesn't care about duplicate name
hoist(.data = df,
  .col = metadata,
  film = list("films", 1L),
  film = list("films", 3L)
)
#> # A tibble: 2 x 4
#>   character film                 film                             metadata      
#>   <chr>     <chr>                <chr>                            <list>        
#> 1 Toothless How to Train Your D… How to Train Your Dragon: The H… <named list […
#> 2 Dory      Finding Nemo         <NA>                             <named list […

This doesn't follow the logic of mutate and simply produces a duplicate name which isn't very nice. So, I think the names in dots should be unique. Alternatively, hoist() could get .names_repair as argument but this is probably confusing with the mutate() behaviour for existing columns.
I am happy to create a PR when this is decided.

[hadley]

Ah yeah, this should definitely be an error.