http-try {tryr}

Client/Server Error Handling

Description

Differentiate between client (4xx) and server (5xx) errors. Provides a mechanism to return custom status codes in combination with http_error() and http_success().

Usage

http_try(req, res, expr, silent = TRUE, ...)

http_try_handler(req, res, x)

Arguments

req

The request object.

res

The response object.

expr

An R expression to try.

silent

Logical, should the report of error messages be suppressed by try()?

...

Arguments passed to try()

x

The return value from try(expr).

Details

If we catch an error:

• the error is a clear server error coming from stop()

  • log it as an ERROR + print the error message to STDERR

  • return a generic status 500 message

  • set the status code of the response object to 500

• the error is a structured HTTP error coming from http_error()

  • log it as an ERROR with the message from the condition attribute

  • return the specific HTTP error code with the structured output

  • set the status code of the response object

If we don't catch an error:

• the object is of class http_success() (this comes in handy for async jobs and redirects)

  • log it as a SUCCESS with the message element

  • return the specific HTTP status code with the structured output

  • set the status code of the response object

• the object is NOT of class http_success()

  • log it as a SUCCESS with a generic 200 message

  • return the object as is (default status code 200 assumed)

Value

A list or the results from expr. A side effect is setting of the response status code on the response object and a log message to STDOUT or STDERR.

See Also

try(), msg()

Examples

req <- new.env()
res <- new.env()

http_try(req, res)
res$status

http_try(req, res, { 2 + 2 })
res$status

http_try(req, res, http_error(401))
res$status

http_try(req, res, http_success(201))
res$status

http_try(req, res, { lm(NULL) })
res$status

http_try(req, res, { stop("Stop!!!") })
res$status


f <- function() stop("Stop!!!")
http_try(req, res, { f() })
res$status

http_try_handler(req, res, { try(f()) })
res$status