Can't dispatch methods with vctrs internals to S7 objects

[Samuel Calderon]

I'm developing on top of {S7} and finding difficult to dispath methods based on vctrs to be used with S7 data.frames. You can see the initial discussion on the S7 repo here: RConsortium/S7#367

Here is a comparison between a S3 and a S7 child class of data.frame using vec_slice(), vec_assert() and obj_check_vector().

library(S7)
library(vctrs)
#> Warning: package 'vctrs' was built under R version 4.3.1

foo_S3 <- function(x = data.frame()) {
    class(x) <- c("foo_S3", class(x))
    x
}

foo_S7 <- new_class("foo_S7", parent = class_data.frame)

base_df <- data.frame(x = seq(5, 1), y = letters[1:5], z = rep(c("A", "B"), times = c(2, 3)))
bar_S3 <- foo_S3(base_df) 
bar_S7 <- foo_S7(base_df)


# they both inherit from data.frame 
class(bar_S3)
#> [1] "foo_S3"     "data.frame"
class(bar_S7)
#> [1] "foo_S7"     "data.frame" "S7_object"


vec_slice(bar_S3, 1:3)
#>   x y z
#> 1 5 a A
#> 2 4 b A
#> 3 3 c B
vec_slice(bar_S7, 1:3)
#> Error in `vec_slice()`:
#> ! `x` must be a vector, not a <foo_S7/data.frame/S7_object> object.
#> Backtrace:
#>     ▆
#>  1. ├─vctrs::vec_slice(bar_S7, 1:3)
#>  2. └─vctrs:::stop_scalar_type(`<fn>`(`<foo_S7[,3]>`), "x", `<env>`)
#>  3.   └─vctrs:::stop_vctrs(...)
#>  4.     └─rlang::abort(message, class = c(class, "vctrs_error"), ..., call = call)


vec_assert(bar_S3) # no output
vec_assert(bar_S7)
#> Error:
#> ! `bar_S7` must be a vector, not a <foo_S7/data.frame/S7_object> object.
#> Backtrace:
#>     ▆
#>  1. └─vctrs::vec_assert(bar_S7)
#>  2.   └─vctrs:::stop_scalar_type(x, arg, call = call)
#>  3.     └─vctrs:::stop_vctrs(...)
#>  4.       └─rlang::abort(message, class = c(class, "vctrs_error"), ..., call = call)


obj_check_vector(bar_S3) # no output
obj_check_vector(bar_S7)
#> Error:
#> ! `bar_S7` must be a vector, not a <foo_S7/data.frame/S7_object> object.
#> Backtrace:
#>     ▆
#>  1. ├─vctrs::obj_check_vector(bar_S7)
#>  2. └─vctrs:::stop_scalar_type(`<fn>`(`<foo_S7[,3]>`), "bar_S7", `<env>`)
#>  3.   └─vctrs:::stop_vctrs(...)
#>  4.     └─rlang::abort(message, class = c(class, "vctrs_error"), ..., call = call)


sessioninfo::session_info(pkgs = "attached")
#> ─ Session info ───────────────────────────────────────────────────────────────
#>  setting  value
#>  version  R version 4.3.0 (2023-04-21 ucrt)
#>  os       Windows 11 x64 (build 22621)
#>  system   x86_64, mingw32
#>  ui       RTerm
#>  language (EN)
#>  collate  Spanish_Peru.utf8
#>  ctype    Spanish_Peru.utf8
#>  tz       America/Lima
#>  date     2023-09-22
#>  pandoc   3.1.1 @ C:/Program Files/RStudio/resources/app/bin/quarto/bin/tools/ (via rmarkdown)
#> 
#> ─ Packages ───────────────────────────────────────────────────────────────────
#>  package * version date (UTC) lib source
#>  S7      * 0.1.1   2023-09-17 [1] CRAN (R 4.3.0)
#>  vctrs   * 0.6.3   2023-06-14 [1] CRAN (R 4.3.1)
#> 
#>  [1] C:/Users/dgco93/AppData/Local/R/win-library/4.3
#>  [2] C:/Program Files/R/R-4.3.0/library
#> 
#> ──────────────────────────────────────────────────────────────────────────────

^{Created on 2023-09-22 with reprex v2.0.2}