What is the purpose of this pull request? (put an "X" next to item)

• Documentation update
• Bug fix (template)
• New rule (template)
• Changes an existing rule (template)
• Add autofixing to a rule
• Add a CLI option
• Add something to the core
• Other, please explain:

What rule do you want to change?
function-paren-newline

How will the change be implemented? (New option, new default behavior, etc.)?
New option consistent-arguments.

What changes did you make? (Give an overview)

"consistent-arguments" requires consistent usage of linebreaks for each pair of parentheses and parameters/arguments. It allows linebreaks inside function parentheses if there is only one parameter/argument.

Examples of incorrect code for this rule with the "consistent-arguments" option:

/* eslint function-paren-newline: ["error", "consistent-arguments"] */

function foo(bar,
  baz
) {}

var foo = function(bar,
  baz
) {};

var foo = (
  bar,
  baz) => {};

foo(
  bar,
  baz);

foo(
  bar, qux,
  baz
);

Examples of correct code for this rule with the consistent "consistent-arguments" option:

/* eslint function-paren-newline: ["error", "consistent-arguments"] */

function foo(
  bar,
  baz
) {}

var foo = function(bar, baz) {};

var foo = (
  bar
) => {};

foo(
  function() {
    return baz;
  }
);

Is there anything you'd like reviewers to focus on?

There are some issues about this problem :: #9286 :: #9411

For multiline option this is obvious behavior when you can use single argument on their own line. But now for this you should use less strict consistent option.

console.log(foo,
  bar,
  baz);

Airbnb JavaScript Style Guide define this code as bad. But their eslint config now use consistent option that miss many bad cases because multiline option disallow to use single argument on their own line. Until then they were forced to use additional parens as workaround.