End iteration for blank cursor

[jonthegeek]

iterate_with_cursor() checks that the next cursor is NULL. I've had to build in a check to convert empty strings "" to NULL, for example for the Slack API. Would it be acceptable to build that into the default checker?
https://github.com/r-lib/httr2/blob/main/R%2Fiterate-helpers.R#L100

The same idea likely also occurs for iterate_with_link_url().

[hadley]

Can you point me to the docs or show an example?

[jonthegeek]

You can kinda see it in the example response here: https://api.slack.com/methods/admin.apps.requests.list

I'll pull up specific examples when I'm back on my laptop.

[jonthegeek]

And this is where I clean it up: https://github.com/jonthegeek/slackapi/blob/main/R%2F040-pagination.R

[hadley]

Given that you already have to write a function to extract it and this is a bit of a special case, I think your package is the right place for the code. I'd write it like this:

.iterator_fn_cursor <- function() {
  httr2::iterate_with_cursor(
    "cursor",
    resp_param_value = function(resp) {
      cursor <- httr2::resp_body_json(resp)$response_metadata$next_cursor
      fix_cursor(cursor)
    }
  )
}

fix_cursor <- function(x) {
  if (identical(cursor, "")) {
    NULL
  } else {
    cursor
  }
}