Add Style/EmptyLineAfterMagicComment cop

[backus]

Depends on rubocop/ruby-style-guide#616

---

Before submitting the PR make sure the following are checked:

• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Used the same coding conventions as the rest of the project.
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Added an entry to the Changelog if the new code introduces user-observable changes. See changelog entry format.
• All tests are passing.
• The new code doesn't generate RuboCop offenses.
• The PR relates to only one subject with a clear title
  and description in grammatically correct, complete sentences.
• Updated cop documentation with rake generate_cops_documentation (required only when you've added a new cop or changed the configuration/documentation of an existing cop).

[backus]

Looks like this touches more tests than I thought. Work in progress....

[rrosenblum]

What are your thoughts on writing this as

inspect_source(cop, ["# frozen_string_literal: true",
                     '',
                     'class Foo; end'])

In my mind, it is a little clearer that there is an empty line between the comment and the class.

[backus]

Yeah I'm fine with either just didn't know what was the convention

[rrosenblum]

Should this be configurable so that the user can choose whether they want to enforce having an empty line or not having an empty line?

I don't think that I saw a test that includes a magic comment and documentation comment. Should the following code register an offense?

# frozen_string_literal: true
# Class documentation
class Foo
end

[Drenmi]

I don't think that I saw a test that includes a magic comment and documentation comment. Should the following code register an offense?

# frozen_string_literal: true
# Class documentation
class Foo
end

IMHO, it should. To me, the lack of spacing would indicate that both comment lines pertain to Foo, which is not the case, here.

[backus]

Yeah good catch guys I also need to add a test case for separating the frozen_string_literal comment from the class documentation

[backus]

@bbatsov build is passing finally minus this weird jruby bug that is plaguing every build.

[backus]

@Drenmi and @rrosenblum I think I addressed your concerns