Parenthesized forwarded args in Style/MethodCallWithArgsParentheses omit_parentheses

[gsamokovarov]

The new-style arguments delegation included in Ruby 2.7 and expanded in
Ruby 3.0 is required to be parenthesized, since the syntax is clashing with the
endless start... range, which can be started with start ... as well. Currently,
the most iffy cop of them all is issuing offenses for:

def delegated_call(...)
  @proxy.call(...)
             ^^^^^ Omit parentheses for method calls with arguments.
end

Removing the parens will start an endless range with the beginning being the
result of the method call without arguments. See the parse trees below for more
details:

-> ruby-parse -e "def foo(...); bar(...); end"
(def :foo
  (args
    (forward-arg))
  (send nil :bar
    (forwarded-args)))

-> ruby-parse -e "def foo(...); bar ...; end"
(def :foo
  (args
    (forward-arg))
  (erange
    (send nil :bar) nil))

-> ruby-parse -e "def foo(...); bar...; end"
(def :foo
  (args
    (forward-arg))
  (erange
    (send nil :bar) nil))

We don't want that, so allow the parentheses and leave this gotcha to
the poor developer that's gonna run onto it.

[bbatsov]

The new-style arguments delegation included in Ruby 2.7 and expanded in
Ruby 3.0 is required to be parenthesized, since the syntax is clashing with the
endless start... range, which can be started with start ... as well.

I'd add something along those lines to the cop's documentation.

the most iffy cop of them all

Well said! This has to be the cop with the most special cases and bugs in the history of RuboCop! 😆

[gsamokovarov]

But boy, do we love this style in Dext! Maybe there is a better approach to tackle the parentheses omission as in this form we have to enumerate the cases where omitting them leads to ambiguous or invalid code. 😅

I have updated the docs to hint that there are other cases we allow parentheses even if we are enforcing the omit_parentheses style.

[bbatsov]

Thanks!