Change the start label of a heredocument to be enclosed in single quotes

[ydah]

This PR is change as follows

# bad - This would require escaping inside heredoc. 
expect_offense(<<-RUBY)
  it 'should do something ' \\ <---here
  ^^^^^^^^^^^^^^^^^^^^^^^ Do not use should when describing your tests.
    'and correctly fix' do
  end
RUBY

# good - This makes the heredoc readable with no need for escaping inside it.
expect_offense(<<-'RUBY')
  it 'should do something ' \
  ^^^^^^^^^^^^^^^^^^^^^^^ Do not use should when describing your tests.
    'and correctly fix' do
  end
RUBY

---

Before submitting the PR make sure the following are checked:

• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• [-] Updated documentation.
• [-] Added an entry to the CHANGELOG.md if the new code introduces user-observable changes.
• The build (bundle exec rake) passes (be sure to run this locally, since it may produce updated documentation that you will need to commit).

[pirj]

There is a difference at a glance. Wondering how it turns out that both work 🤔

<<~A
/^when\b/
A
=> "/^when\b/\n"
<<~'A'
/^when\b/
A
=> "/^when\\b/\n"

Maybe there's some escaping logic in expect_offense? I can't find any code in expect_offense and there are no specs for this method or AnnotatedSource in rubocop specs.

[ydah]

The argument of expect_offense is a heap document, so a heap document enclosed in single quotes is completely a string as written. So the following would be the same.

irb(main):001:0" <<~A
irb(main):002:0" /^when\\b/
irb(main):003:0> A
=> "/^when\\b/\n"
irb(main):004:0' <<~'A'
irb(main):005:0' /^when\b/
irb(main):006:0> A
=> "/^when\b/\n"

Am I missing something?

[pirj]

Oh, please accept my apologies, I've missed the point that you've changed the contents of the string and removed unnecessary escaping.
Looks much better this way indeed!

[ydah]

The title of this PR was misleading. My apologies.
Thanks for the review!

[bquorning]

Please add to the PR description what the benefit/downside is of either syntax. I always forget which is which.

[ydah]

Thank you for review. I updated description.

[pirj]

<<-A
a \
b
A
=> "a b\n"

The \ part is lost, and that undermines the very existence of this example which is purposed to test "-separated multiline strings".

[ydah]

The results seem to be the same here as well.

irb(main):001:0" <<-A
irb(main):002:0" a \\
irb(main):003:0" b
irb(main):004:0> A
=> "a \\\nb\n"
irb(main):005:0' <<-'A'
irb(main):006:0' a \
irb(main):007:0' b
irb(main):008:0> A
=> "a \\\nb\n"

[ydah]

The title of the PR was incorrect and has been corrected.

[pirj]

Much easier to read now, thank you!