Tools to Work with the 'Splash' JavaScript Rendering Service in R
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# Less cool counterparts to purrr's side-effect capture-rs
#
# Most of the helper functions are 100% from output.R in purrr repo
#
# @param quiet Hide errors (`TRUE`, the default), or display them
# as they occur?
# @param otherwise Default value to use when an error occurs.
#
# @return `safely`: wrapped function instead returns a list with
# components `result` and `error`. One value is always `NULL`.
#
# `quietly`: wrapped function instead returns a list with components
# `result`, `output`, `messages` and `warnings`.
#
# `possibly`: wrapped function uses a default value (`otherwise`)
# whenever an error occurs.
safely <- function(.f, otherwise = NULL, quiet = TRUE) {
function(...) capture_error(.f(...), otherwise, quiet)
}
quietly <- function(.f) {
function(...) capture_output(.f(...))
}
possibly <- function(.f, otherwise, quiet = TRUE) {
force(otherwise)
function(...) {
tryCatch(.f(...),
error = function(e) {
if (!quiet)
message("Error: ", e$message)
otherwise
},
interrupt = function(e) {
stop("Terminated by user", call. = FALSE)
}
)
}
}
capture_error <- function(code, otherwise = NULL, quiet = TRUE) {
tryCatch(
list(result = code, error = NULL),
error = function(e) {
if (!quiet)
message("Error: ", e$message)
list(result = otherwise, error = e)
},
interrupt = function(e) {
stop("Terminated by user", call. = FALSE)
}
)
}
capture_output <- function(code) {
warnings <- character()
wHandler <- function(w) {
warnings <<- c(warnings, w$message)
invokeRestart("muffleWarning")
}
messages <- character()
mHandler <- function(m) {
messages <<- c(messages, m$message)
invokeRestart("muffleMessage")
}
temp <- file()
sink(temp)
on.exit({
sink()
close(temp)
})
result <- withCallingHandlers(
code,
warning = wHandler,
message = mHandler
)
output <- paste0(readLines(temp, warn = FALSE), collapse = "\n")
list(
result = result,
output = output,
warnings = warnings,
messages = messages
)
}