dplyr::n() does not work on databases

[JohnMount]

The dplyr::n() notation suggested in https://github.com/tidyverse/dplyr/blob/master/NEWS.md#breaking-changes does not work on database handles.

packageVersion("dplyr")
#> [1] '0.7.8'

# works
dplyr::summarize(data.frame(x = 1), count = dplyr::n())
#>   count
#> 1     1

# fails
db <- DBI::dbConnect(RSQLite::SQLite(), ":memory:")
t <- dplyr::copy_to(db, data.frame(x = 1), "d")
dplyr::summarize(t, count = dplyr::n())
#> Error: This function should not be called directly

^{Created on 2018-12-31 by the reprex package (v0.2.1)}

See also tidyverse/dplyr#4062 .

[hadley]

Moved to dbplyr since that is where the problem lies.

[hadley]

Minimal reprex:

mf <- dbplyr::memdb_frame(x = 1:10)
dplyr::summarise(mf, n = dplyr::n())
#> Error: This function should not be called directly
#> Backtrace:
#>     █
#>  1. ├─dplyr::summarise(mf, n = dplyr::n())
#>  2. ├─dbplyr:::summarise.tbl_lazy(mf, n = dplyr::n())
#>  3. │ └─dbplyr::partial_eval(dots, vars = op_vars(.data))
#>  4. │   ├─rlang::switch_type(...)
#>  5. │   └─dbplyr:::map(call, partial_eval, vars = vars, env = env)
#>  6. │     └─base::lapply(.x, .f, ...)
#>  7. │       └─dbplyr:::FUN(X[[i]], ...)
#>  8. │         ├─rlang::switch_type(...)
#>  9. │         └─dbplyr::partial_eval(f_rhs(call), vars, f_env(call))
#> 10. │           ├─rlang::switch_type(...)
#> 11. │           └─dbplyr:::lang_partial_eval(call, vars, env)
#> 12. │             ├─rlang::switch_lang(...)
#> 13. │             └─rlang::eval_bare(call, env)
#> 14. └─dplyr::n()

^{Created on 2019-01-02 by the reprex package (v0.2.1)}