Basics

This check has a base priority of normal and works with any version of Elixir.

Explanation

Forbids the shorthand def name(args), do: body form whose body spans more than one line. Once the body has to wrap, switch to the explicit do...end block form.

The shorthand exists to keep tiny bodies visually compact. Once the body has to wrap across multiple lines, the , do: punctuation becomes harder to spot than a plain do block — and the resulting layout encourages awkward mid-expression line breaks.

A multi-line head (e.g. from nested pattern matching) is fine as long as the body still fits on a single line.

Bad

def something(x),
  do:
    one_very_long_method_call(x) || one_very_long_method_call(x) ||
      one_very_long_method_call(x)

Good

def something(x) do
  one_very_long_method_call(x) || one_very_long_method_call(x) ||
    one_very_long_method_call(x)
end

# still fine — body is a single line
def short(x),
  do: x + 1

# still fine — only the head wraps; body fits on one line
defp put_id(map, %{
       outer: %{inner: %{id: id}}
     }),
     do: Map.put(map, :id, id)

The check inspects every def, defp, defmacro, and defmacrop that uses the shorthand keyword form. Block-form (do...end) definitions are not considered.

Check-Specific Parameters

There are no specific parameters for this check.

General Parameters

Like with all checks, general params can be applied.

Parameters can be configured via the .credo.exs config file.