Unnecessary escaping of % inside multi-line character in R

[eitsupi]

From pola-rs/r-polars#1065, maybe related to #904

I noticed that Rd files are not generated correctly when % is included within a multi-line string in the example.
I want to examples include % inside multi-line characters something like this:

a <- "%"
b <- "
%
"

For this, the following Rd file is in the correct format.
Note that the second % is not escaped.

\examples{
a <- "\%"
b <- "
%
"
}

However, when roxygen2 generates an Rd file from a comment, the second % is also escaped, so the original example is not restored when converted to another format, such as Rd2txt().

roxygen2::roc_proc_text(
  roxygen2::rd_roclet(),
  r"(
#' sample
#' @examples
#' a <- "%"
#' b <- "
#' %
#' "
foo <- function() 1
)"
)
#> $foo.Rd
#> % Generated by roxygen2: do not edit by hand
#> % Please edit documentation in ./<text>
#> \name{foo}
#> \alias{foo}
#> \title{sample}
#> \usage{
#> foo()
#> }
#> \description{
#> sample
#> }
#> \examples{
#> a <- "\%"
#> b <- "
#> \%
#> "
#> }

^{Created on 2024-04-28 with reprex v2.1.0}