Error message for select() when column doesn't exist

[mine-cetinkaya-rundel]

See below for a reprex for selecting a column that doesn't exist:

library(dplyr)

df <- tibble(x = 1:2, y = 3:4)
df
#> # A tibble: 2 × 2
#>       x     y
#>   <int> <int>
#> 1     1     3
#> 2     2     4
df %>% select(z)
#> Error in `stop_subscript()`:
#> ! Can't subset columns that don't exist.
#> x Column `z` doesn't exist.

^{Created on 2022-02-27 by the reprex package (v2.0.1)}

I think the error should say Can't select columns that don't exist since subset is not the verb used in the code, and it actually means filter() in base R.

[hadley]

It now says

library(dplyr, warn.conflicts = FALSE)

df <- tibble(x = 1:2, y = 3:4)
df %>% select(z)
#> Error in `select()`:
#> ! Can't subset columns that don't exist.
#> ✖ Column `z` doesn't exist.

^{Created on 2022-07-21 by the reprex package (v2.0.1)}

Which I think is about as good as we can get, without customising the underlying vctrs error which would be a lot of work, for relatively little gain, IMO.

[DavisVaughan]

This might not be that hard actually. tidyselect is already renaming it to subset and columns for us:

tidyselect:::with_subscript_errors
#> function (expr, type = "select", call = caller_env()) 
#> {
#>     tryCatch(expr, vctrs_error_subscript = function(cnd) {
#>         cnd$subscript_action <- subscript_action(type)
#>         cnd$subscript_elt <- "column"
#>         cnd_signal(cnd)
#>     })
#> }
#> <bytecode: 0x7f7dbd5df4f0>
#> <environment: namespace:tidyselect>

tidyselect:::subscript_action
#> function (type) 
#> {
#>     switch(validate_type(type), select = "subset", rename = "rename", 
#>         pull = "extract")
#> }
#> <bytecode: 0x7f7ddc4e69e0>
#> <environment: namespace:tidyselect>

So maybe tidyselect should say select = "select" here rather than select = "subset"? @lionel- what do you think?

We'd have to make "select" a valid option in vctrs.

library(dplyr, warn.conflicts = FALSE)

df <- tibble(x = 1:2, y = 3:4)

withCallingHandlers(
  select(df, z),
  vctrs_error_subscript_oob = function(cnd) {
    cnd$subscript_action <- "select"
    rlang::cnd_signal(cnd)
  }
)
#> Error in `cnd_subscript_action()`:
#> ! Internal error: `cnd$subscript_action` must be one of `subset`, `extract`, `assign`, `rename`, `remove`, or `negate`.

Alternatively we can also catch and rethrow the error in select() and make it say "select" too, if we want to keep it as "subset" in tidyselect.

[lionel-]

That sounds good. We'll need a change in both vctrs and tidyselect, I've opened issues.

[hadley]

FWIW I stand by my original comment that this is more trouble than its worth. Having to change three packages in concert to modify a single word in an error message that is already pretty good doesn't feel like a great payoff to me.

[DavisVaughan]

Fine by me