methods/warn_parameters.rb

tests/_examples/methods/warn_parameters.rb in the metorex repository.

# `Kernel#warn` names the keywords it takes.
p Kernel.instance_method(:warn).parameters

# `exception:` takes true or false and nothing else.
reader, writer = IO.pipe
begin
  reader.read_nonblock(4, exception: nil)
rescue ArgumentError => problem
  p problem.message
end
begin
  writer.write_nonblock("x", exception: 0)
rescue ArgumentError => problem
  p problem.message
end
reader.close
writer.close

# `close_others:` and `daemon` arguments take true, false, or nil.
begin
  Process.spawn("true", close_others: 1)
rescue ArgumentError => problem
  p problem.message
end
begin
  Process.daemon("true")
rescue ArgumentError => problem
  p problem.message
end
begin
  Process.daemon(true, "x")
rescue ArgumentError => problem
  p problem.message
end

Output:

[[:rest, :msgs], [:key, :uplevel], [:key, :category]]
"expected true or false as exception: nil"
"expected true or false as exception: 0"
"expected true or false as close_others: 1"
"expected true or false as nochdir: \"true\""
"expected true or false as noclose: \"x\""