Control handling of HTTP errors

req_perform() will automatically convert HTTP errors (i.e. any 4xx or 5xx status code) into R errors. Use req_error() to either override the defaults, or extract additional information from the response that would be useful to expose to the user.

req_error(req, is_error = NULL, body = NULL)

Arguments

req

A request.

is_error

A predicate function that takes a single argument (the response) and returns TRUE or FALSE indicating whether or not an R error should signalled.

body

A callback function that takes a single argument (the response) and returns a character vector of additional information to include in the body of the error. This vector is passed along to the message argument of rlang::abort() so you can use any formatting that it supports.

Value

A modified HTTP request.

See also

req_retry() to control when errors are automatically retried.

Examples

# Performing this request usually generates an error because httr2
# converts HTTP errors into R errors:
req <- request("http://httpbin.org/404")
try(req %>% req_perform())
#> Error : HTTP 404 Not Found.
# You can still retrieve it with last_response()
last_response()
#> <httr2_response>
#> GET http://httpbin.org/404
#> Status: 404 Not Found
#> Content-Type: text/html
#> Body: In memory (233 bytes)

# But you might want to suppress this behaviour:
resp <- req %>%
  req_error(is_error = function(resp) FALSE) %>%
  req_perform()
resp
#> <httr2_response>
#> GET http://httpbin.org/404
#> Status: 404 Not Found
#> Content-Type: text/html
#> Body: In memory (233 bytes)

# Or perhaps you're working with a server that routinely uses the
# wrong HTTP error codes only 500s are really errors
request("http://example.com") %>%
  req_error(is_error = function(resp) resp_status(resp) == 500)
#> <httr2_request>
#> GET http://example.com
#> Body: empty
#> Policies:
#> • error_is_error: a function

# Most typically you'll use req_error() to add additional information
# extracted from the response body (or sometimes header):
error_body <- function(resp) {
  resp_body_json(resp)$error
}
request("http://example.com") %>%
  req_error(body = error_body)
#> <httr2_request>
#> GET http://example.com
#> Body: empty
#> Policies:
#> • error_body: a function
# Learn more in vignette("wrapping-apis")