kvasilopoulos/cran-policy.txt

## cran-policy.txt
CRAN policy:

''Packages which use Internet resources should fail gracefully with an
informative message if the resource is not available (and not give a
check warning nor error).'


## file.R
library(httr)
library(curl)

gracefully_fail <- function(remote_file) {
  try_GET <- function(x, ...) {
    tryCatch(
      GET(url = x, timeout(1), ...),
      error = function(e) conditionMessage(e),
      warning = function(w) conditionMessage(w)
    )
  }
  is_response <- function(x) {
    class(x) == "response"
  }

  # First check internet connection
  if (!curl::has_internet()) {
    message("No internet connection.")
    return(invisible(NULL))
  }
  # Then try for timeout problems
  resp <- try_GET(remote_file)
  if (!is_response(resp)) {
    message(resp)
    return(invisible(NULL))
  }
  # Then stop if status > 400
  if (httr::http_error(resp)) {
    message_for_status(resp)
    return(invisible(NULL))
  }

  # If you are using rvest as I do you can easily read_html in the response
  xml2::read_html(resp)
}

gracefully_fail("http://httpbin.org/status/404") # http >400
#> Not Found (HTTP 404).
gracefully_fail("http://httpbin.org/delay/2") # Timeout
#> Timeout was reached: [httpbin.org] Operation timed out after 1000 milliseconds with 0 bytes received
gracefully_fail("http://httpbin.org") #OK
#> {html_document}
#> <html lang="en">
#> [1] <head>\n<meta http-equiv="Content-Type" content="text/html; charset=UTF-8 ...
#> [2] <body>\n    <a href="https://github.com/requests/httpbin" class="github-c ...

## helpers.R
skip_if_http_error <- function() {
  remote_file <- "https://www.nationwide.co.uk/about/house-price-index/download-data"
  skip_if(httr::http_error(remote_file))
}

 skip_if_offline()
 skip_if_http_error()
	CRAN policy:

	''Packages which use Internet resources should fail gracefully with an
	informative message if the resource is not available (and not give a
	check warning nor error).'
	library(httr)
	library(curl)

	gracefully_fail <- function(remote_file) {
	try_GET <- function(x, ...) {
	tryCatch(
	GET(url = x, timeout(1), ...),
	error = function(e) conditionMessage(e),
	warning = function(w) conditionMessage(w)
	)
	}
	is_response <- function(x) {
	class(x) == "response"
	}

	# First check internet connection
	if (!curl::has_internet()) {
	message("No internet connection.")
	return(invisible(NULL))
	}
	# Then try for timeout problems
	resp <- try_GET(remote_file)
	if (!is_response(resp)) {
	message(resp)
	return(invisible(NULL))
	}
	# Then stop if status > 400
	if (httr::http_error(resp)) {
	message_for_status(resp)
	return(invisible(NULL))
	}

	# If you are using rvest as I do you can easily read_html in the response
	xml2::read_html(resp)
	}

	gracefully_fail("http://httpbin.org/status/404") # http >400
	#> Not Found (HTTP 404).
	gracefully_fail("http://httpbin.org/delay/2") # Timeout
	#> Timeout was reached: [httpbin.org] Operation timed out after 1000 milliseconds with 0 bytes received
	gracefully_fail("http://httpbin.org") #OK
	#> {html_document}
	#> <html lang="en">
	#> [1] <head>\n<meta http-equiv="Content-Type" content="text/html; charset=UTF-8 ...
	#> [2] <body>\n <a href="https://github.com/requests/httpbin" class="github-c ...
	skip_if_http_error <- function() {
	remote_file <- "https://www.nationwide.co.uk/about/house-price-index/download-data"
	skip_if(httr::http_error(remote_file))
	}

	skip_if_offline()
	skip_if_http_error()