group_by_prepare with default error_call argument results in error

[eutwt]

The default values for arguments caller_env and error_call in group_by_prepare don't seem to work

group_by_prepare with default error_call

df <- data.frame(x = 1)
dplyr::group_by_prepare(df)
#> Error in is_missing(call): promise already under evaluation: recursive default argument reference or earlier problems?

^{Created on 2022-08-31 with reprex v2.0.2}

with error_call supplied but not caller_env, adding a column

df <- data.frame(x = 1)
dplyr::group_by_prepare(df, y = 3, error_call = call('fun'))
#> Error in initialize(...): promise already under evaluation: recursive default argument reference or earlier problems?

^{Created on 2022-08-31 with reprex v2.0.2}

The reason I noticed this is that group_by_prepare(data.frame(x = 1)) works with CRAN dplyr but not dev dplyr, which causes group_by to fail in dtplyr if dev dplyr is installed.

It seems to be because caller_env is self-referencing in the function signature. I guess the users of this function would be package developers who can probably figure out what's going on and just supply the arguments, but it was a little confusing. Maybe these arguments could have no default to make the error more understandable (argument "caller_env" is missing rather than promise already under evaluation), or caller_env renamed to .caller_env.

dplyr/R/group-by.r

Lines 193 to 199 in 48431a5

	group_by_prepare <- function(.data,
	...,
	caller_env = caller_env(2),
	.add = FALSE,
	.dots = deprecated(),
	add = deprecated(),
	error_call = caller_env()) {

fun <- function(caller_env = caller_env(2)) {
  print(caller_env)
}
fun()
#> Error in print(caller_env): promise already under evaluation: recursive default argument reference or earlier problems?

^{Created on 2022-08-31 with reprex v2.0.2}

[hadley]

Ended up accidentally fixing this in #6444.