feat: add httr2_translate

[JosiahParry]

This PR closes #795 by adding an httr2_translate() function.

This function takes an httr2_request object and does its best to faithfully create the equivalent curl request while respecting headers, cookies, options, request type etc.

library(httr2)

request("https://httpbin.org/post") |>
  req_body_form(name = "value") |>
  httr2_translate() |>
  cat()
#> curl -X POST \
#>   -H "Content-Type: application/x-www-form-urlencoded" \
#>   -d "name=value" \
#>   "https://httpbin.org/post"

path <- tempfile()
writeLines("test content", path)
request("https://httpbin.org/post") |>
  req_body_file(path, type = "text/plain") |>
  httr2_translate() |>
  cat()
#> curl -X POST \
#>   -H "Content-Type: text/plain" \
#>   --data-binary "@/var/folders/wd/xq999jjj3bx2w8cpg7lkfxlm0000gn/T//Rtmp6Xs5Mq/file13ec039518760" \
#>   "https://httpbin.org/post"

request("https://httpbin.org/get") |>
  req_options(timeout = 30, verbose = TRUE, ssl_verifypeer = FALSE) |>
  httr2_translate() |>
  cat()
#> curl --max-time 30 \
#>   --verbose \
#>   --insecure \
#>   "https://httpbin.org/get"

request("https://httpbin.org/get") |>
  req_headers("Authorization" = obfuscated("ZdYJeG8zwISodg0nu4UxBhs")) |>
  httr2_translate() |>
  cat()
#> curl -H "Authorization: y" \
#>   "https://httpbin.org/get"

^{Created on 2025-08-20 with reprex v2.1.1}

[JosiahParry]

CI has been tamed. Please let me know if there is anything I can do to move this along! I'd quite like to be able to use it as a debug option in {arcgislayers} with something like:

if (isTRUE(getOption("arcgis.debug_curl")) {
    cat(httr2::httr2_translate(req))
}

This will help tremendously in getting reproducible examples from users as well as providing them to our distributed team of software engineers.

Thanks!

[hadley]

Is this branch actually necessary?

[JosiahParry]

This branch is used so that the output is compatible with curl_translate() if curl is on its own line curl_translate() fails to read the result.

[hadley]

I understand that but I think if remove the first branch then the results will still be the same.

I'd suggest renaming and refocussing cmd_parts to curl_args (i.e. adding curl and the url at the very end) to make this more clear.

[JosiahParry]

Thank you so much for the feedback! I'll review this and make the requested changes.

[hadley]

Again, you don't need to first check if the vector is empty, if it is empty the for loop already doesn't do anything.

[hadley]

I'd suggest making this a separate function

[hadley]

If x is empty, then "foo" %in% x will always return FALSE.