register_parser: Register or fetch a parser

Description

plumber2 comes with many parsers that should cover almost all standard use cases. Still you might want to provide some of your own, which this function facilitates.

Usage

register_parser(name, fun, mime_types, default = TRUE)
show_registered_parsers()
get_parsers(parsers = NULL)

Value

For get_parsers a named list of parser functions named by their mime types. The order given in parsers is preserved.

Arguments

name

The name to register the parser function to. If already present the current parser will be overwritten by the one provided by you

fun

A function that, when called, returns a binary function that can parse a request body. The first argument takes a raw vector with the binary encoding of the request body, the second argument takes any additional directives given by the requests Content-Type header

mime_types

One or more mime types that this parser can handle. The mime types are allowed to contain wildcards, e.g. "text/*"

default

Should this parser be part of the default set of parsers

parsers

Parsers to collect. This can either be a character vector of names of registered parsers or a list. If it is a list then the following expectations apply:

Any unnamed elements containing a character vector will be considered as names of registered parsers constructed with default values. The special value "..." will fetch all the parsers that are otherwise not specified in the call
Any element containing a function are considered as a provided parser and the element must be named by the mime type the parser understands (wildcards allowed)
Any remaining named elements will be considered names of registered parsers that should be constructed with the arguments given in the element

Details

If you want to register your own parser, then the function you register must be a factory function, i.e. a function returning a function. The returned function must accept two arguments, the first being a raw vector corresponding to the request body, the second being the parsed directives from the request Content-Type header. All arguments to the factory function should be optional.

Examples

Run this code

# Register a parser that splits at a character and converts to number
register_parser("comma", function(delim = ",") {
  function(raw, directive) {
    as.numeric(strsplit(rawToChar(raw), delim)[[1]])
  }
}, mime_types = "text/plain", default = FALSE)