How to send json response using plumber R

Question

I need to send response from R using plumber package in below format

{
  "status": "SUCCESS",
  "code": "200",
  "output": {
    "studentid": "1001",
    "name": "Kevin"
  }
}

But I am getting below format

[
  "{\n  \"status\": \"SUCCESS\",\n  \"code\": \"200\",\n  \"output\": {\n    \"studentid\": \"1001\",\n    \"name\": \"Kevin\"\n  }\n}"
]

Please help me format this json properly

My Code

#* @post /sum
addTwo <- function(){
  library(jsonlite)
  x <- list(status = "SUCCESS", code = "200",output = list(studentid = "1001", name = "Kevin"))
  output<-toJSON(x,pretty = TRUE, auto_unbox = TRUE)
  return (output)
}

Answer 1

Just remove the toJSON() wrapper. Plumber already does JSON serialisation so you are doing it twice by adding a toJSON function.

This should work.

 addTwo <- function(){
  x <- list(status = "SUCCESS", code = "200",output = list(studentid = "1001", name = "Kevin"))
  return (x)
}

Answer 2

I added an unboxedJSON serializer to the development version of plumber. Depending on when in the future this is being read, that serializer might have been published to CRAN and might even be the default serializer now (I'm still debating).

But for now, you can install the development version from GitHub (devtools::install_github("trestletech/plumber")) then add the @serializer unboxedJSON annotation to your function like so:

#* @post /sum
#* @serializer unboxedJSON
addTwo <- function(){
  list(status = "SUCCESS", code = "200",output = list(studentid = "1001", name = "Kevin"))

}

FYI if you ever do want to force plumber to return some text that you're providing directly, you should be able to set the $body element on res then return the res object from the function.

#* @get /
function(res){
  res$body <- "I am raw"
  res
}

which will return the unformatted, unserialized text I am raw in its response.