Undocumented S3 Method Check Fails when srcrefs are Missing

[smilberg]

Running roxygenize on a package with undocumented S3 methods and without srcrefs fails as follows:

Error in map2(undocumented, names(undocumented), function(fun, name) { : 
  ℹ In index: 1.
ℹ With name: c.blah.
Caused by error in `basename()`:
! a character vector argument expected

The error relates to the addition of checks for undocumented S3 methods from #1534 which implicitly assumes srcrefs are always present. Downstream code then fails because it gets NULL instead of a string.

Recreating the error is a bit tricky b/c we need a package without srcrefs, but here is a reasonably small example that reproduces the error:

pkg.name <- 'pkguqhr'
DESCRIPTION <- sprintf('
Package: %s
Version: 0.0
Encoding: UTF-8
Roxygen: list(load="installed")', pkg.name)
NAMESPACE <- ''
RCODE <- 'c.blah <- function(...) NULL'
if(!pkg.name %in% rownames(installed.packages())) {
  pkg.dir <- tempfile(pkg.name)
  dir.create(file.path(pkg.dir, "R"), recursive=TRUE)
  writeLines(DESCRIPTION, file.path(pkg.dir, 'DESCRIPTION'))
  writeLines(NAMESPACE, file.path(pkg.dir, 'NAMESPACE'))
  writeLines(RCODE, file.path(pkg.dir, 'R', 'pkg.R'))

  install.packages(pkg.dir, type='src', repos=NULL, quiet=TRUE)
  try(roxygen2::roxygenise(pkg.dir))
  remove.packages(pkg.name)
} else {
  stop(
    "Please either remove ", pkg.name, 
    " or find another name for this test package"
  )
}

Notice the Roxygen: list(load="installed"). Assuming the above is in test.R then:

R --vanilla -q -f test.R

Reproduces the error.

Relates to #1589. #1711 provides a simple fix, but probably better would be to have an accessor function for srcrefs that is guaranteed to return in standard format, and then use that function everywhere, but that's a bigger change.