Change AllowAdjacentOneLineDefs config parameter of Layout/EmptyLineBetweenDefs to true by default

[koic]

This PR changes AllowAdjacentOneLineDefs config parameter of Layout/EmptyLineBetweenDefs to true by default.

Currently, warnings that occur are different for each type of definition grouped as shown below.

% cat example.rb
class FooError < StandardError; end
class BarError < StandardError; end
class BazError < StandardError; end

attr_accessor :foo
attr_accessor :bar
attr_accessor :baz

before_action :do_foo
before_action :do_bar
before_action :do_baz

% bundle exec rubocop
(snip)

Inspecting 1 file
C

Offenses:

example.rb:1:1: C: [Correctable] Style/FrozenStringLiteralComment:
Missing frozen string literal comment.
class FooError < StandardError; end
^
example.rb:2:1: C: [Correctable] Layout/EmptyLineBetweenDefs: Expected 1
empty line between class definitions; found 0.
class BarError < StandardError; end
^^^^^^^^^^^^^^
example.rb:3:1: C: [Correctable] Layout/EmptyLineBetweenDefs: Expected 1
empty line between class definitions; found 0.
class BazError < StandardError; end
^^^^^^^^^^^^^^

1 file inspected, 3 offenses detected, 3 offenses auto-correctable

This AllowAdjacentOneLineDefs: true makes it consistent so that there are no blank lines when grouped by one liner definitions.

---

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• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
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• Squashed related commits together.
• Added tests.
• Ran bundle exec rake default. It executes all tests and runs RuboCop on its own code.
• Added an entry (file) to the changelog folder named {change_type}_{change_description}.md if the new code introduces user-observable changes. See changelog entry format for details.

[bbatsov]

I find the example code confusing:

class FooError < StandardError; end
class BarError < StandardError; end
class BazError < StandardError; end

attr_accessor :foo
attr_accessor :bar
attr_accessor :baz

before_action :do_foo
before_action :do_bar
before_action :do_baz

There's just one type of definition here and the macro methods. I thought the cop applies just to class/module/def. I might be misunderstanding the problem the change aims to solve.

[koic]

Oh, I'm sorry. My explanation was not good. It was the behavior when running rubocop command including other entire cops by default, not just Layout/EmptyLineBetweenDefs cop.
So, I would like to convey that it would be better for grouped one-liners case to have no blank lines.

[bbatsov]

Makes sense to me in general. Is this something that requires changes/new examples to the style guide as well?

[bbatsov]

I guess it'd be nice to put both good and bad examples for the option. I see now with true have only good and with false only bad.

[koic]

There are no bad cases because AllowAdjacentOneLineDefs: true only increases allowed good cases.
AllowAdjacentOneLineDefs: true and AllowAdjacentOneLineDefs: false add the same good case.
In any case, I've updated it and AllowAdjacentOneLineDefs: false's example is more clearer :-)

[koic]

Makes sense to me in general. Is this something that requires changes/new examples to the style guide as well?

Good point! I will also take a look at the guide.