[R] Improve error message when providing a mix of readr and Arrow options

[asfimport]

I was trying to solve a user issue today and tried to run the following code:

df = tibble(x = c("a","b",  ""  , "d"))
write_tsv(df, "data.tsv")
open_dataset("data.tsv", format="tsv", skip_rows=1, schema=schema(x=string()), skip_empty_rows = TRUE) %>%
  collect()

which gives me the error

Error: Use either Arrow parse options or readr parse options, not both

which is somewhat obnoxious as I have literally no context provided to know which options are being referred to and what the possible options are.

Also, like, why can't we have a mix of both? This is a totally valid use-case. I think both a code update and a more informative error message are needed here.

Reporter: Nicola Crane / @thisisnic

_{Note: This issue was originally created as ARROW-18236. Please see the migration documentation for further details.}

[thisisnic]

Note: an improved error message has already been implemented for the CSV reading options, so this would need something similar.

Here's the code which improves the messages for the CSV reading:

arrow/r/R/dataset-format.R

Lines 440 to 454 in b413ac4

	if (any(is_readr_opt)) {
	# Catch cases when the user specifies a mix of Arrow C++ options and
	# readr-style options
	if (!all(is_readr_opt)) {
	abort(c(
	"Additional CSV reading options must be Arrow-style or readr-style, but not both.",
	i = sprintf("Arrow options used: %s.", oxford_paste(opt_names[is_arrow_opt])),
	i = sprintf("readr options used: %s.", oxford_paste(opt_names[is_readr_opt]))
	))
	}
	do.call(readr_to_csv_read_options, opts) # all options have readr-style names
	} else {
	do.call(CsvReadOptions$create, opts) # all options have Arrow C++ names
	}
	}