This module defines default command line parsers for primitive types as expected by cmdline.

These parsers are employed when using typed parsers, for example, in:

cli.flagBuilder()
  .parser(int, proc (opt: string, value: int, c: var Result) = discard)

parseCli(int, input) will be called on the input string from the command line before being handed over to the registered parser.

cmdline expects custom parsers to employ the following signature:

proc parseCli(T: typedesc[CustomType], value: string): T

The custom parser shall raise ValueError if value could not be correctly parsed as CustomType.

Example:

import experimental/cmdline/parsers
import experimental/cmdline
import std/json
import std/sugar

## This example implements `parseCli` for type `Custom`

type Custom = object
  i: int

proc parseCli(T: typedesc[Custom], value: string): T =
  let jnode = parseJson(value)
  try:
    result = jnode.to(T)
  except CatchableError as err:
    raise newException(ValueError):
      "'" & value & "' is invalid: " & err.msg

var cli = commandBuilder(Custom)
  .initCli()
cli.positionalBuilder()
  .name("VALUE")
  .describe("JSON form of Custom")
  .parser(Custom, (v, var c) => (c = v))
  .addTo(cli)

doAssert cli.parse(@["""{"i": 10}"""]) == Custom(i: 10)
doAssertRaises(InvalidPositionalError):
  discard cli.parse(@["not-json"])
doAssertRaises(InvalidPositionalError):
  discard cli.parse(@["""{"x": 10}"""])