Fix deactivated StyleGuideBaseURL for Layout/ClassStructure

[aeroastro]

StyleGuide config for Layout/ClassStructure was
written as an absolute URL instead of a relative URL.
This prevents custom StyleGuideBaseURL from taking precedence
over original rubocop-hq URL.

https://github.com/rubocop-hq/rubocop/blob/86f35b21a9de380028bc7bc7cf1a6e212106e6b9/config/default.yml#L74-L76

This patch fix the issue by specifying fragment as the
StyleGuide of Layout/ClassStructure.

Since this is a bug fix in default config, I think we can omit a test.
If required, please let me know.

---

Before submitting the PR make sure the following are checked:

• Wrote [good commit messages][1].
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• 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.
• The PR relates to only one subject with a clear title
  and description in grammatically correct, complete sentences.
• Run bundle exec rake default. It executes all tests and RuboCop for itself, and generates the documentation.

[aeroastro]

Sorry, it seems like I had uncommitted changes in my local workspace. Now all the diff is uploaded.

[koic]

Change log entry is not required because there is no impact to users.

[aeroastro]

Thank you for the quick review. 🐱
Although the impact is small, this actually affect some portion of users. Sorry for not providing detailed information.

Prerequisites

Let's assume we have the following .rubocop.yml and the target test.rb.

AllCops:
  StyleGuideBaseURL: https://github.com/aeroastro/ruby-style-guide
Layout/ClassStructure:
  Enabled: true

# :nodoc:
class Test
  private

  def hoge
  end

  HOGE = 3
end

The reason why I changed the StyleGuideBaseURL is:

• We are using a project-specific ruby style guide
• We want all the ruby style guide URL to be linked to the new URL.

c.f #3535

Impact

Then, run rubocop with --display-style-guide option to show the style guide URL.
This generates the following offense messages. (I removed the warn message of Performance Cop for simplicity.)

$ ruby -v
ruby 2.4.2p198 (2017-09-14 revision 59899) [x86_64-darwin16]
$ bundle exec rubocop -v
0.66.0
$ bundle exec rubocop --display-style-guide test.rb

Before

Inspecting 1 file
C

Offenses:

test.rb:5:3: C: Style/EmptyMethod: Put empty method definitions on a single line. (https://github.com/aeroastro/ruby-style-guide#no-single-line-methods)
  def hoge ...
  ^^^^^^^^
test.rb:8:3: C: Layout/ClassStructure: constants is supposed to appear before private_methods. (https://github.com/rubocop-hq/ruby-style-guide#consistent-classes)
  HOGE = 3
  ^^^^^^^^

1 file inspected, 2 offenses detected

After

Inspecting 1 file
C

Offenses:

test.rb:5:3: C: Style/EmptyMethod: Put empty method definitions on a single line. (https://github.com/aeroastro/ruby-style-guide#no-single-line-methods)
  def hoge ...
  ^^^^^^^^
test.rb:8:3: C: Layout/ClassStructure: constants is supposed to appear before private_methods. (https://github.com/aeroastro/ruby-style-guide#consistent-classes)
  HOGE = 3
  ^^^^^^^^

1 file inspected, 2 offenses detected

You can see that the style guide URL of LayoutClassStructure is now successfully linked to custom ruby style guide, https://github.com/aeroastro/ruby-style-guide#consistent-classes instead of https://github.com/rubocop-hq/ruby-style-guide#consistent-classes

Additional Information

On the current master, only Layout/ClassStructure has duplicate URL definition.
So this fixes the last one.

# on current master
$ grep -C 2 'https://github.com/rubocop-hq/ruby-style-guide' config/default.yml
  # When specifying style guide URLs, any paths and/or fragments will be
  # evaluated relative to the base URL.
  StyleGuideBaseURL: https://github.com/rubocop-hq/ruby-style-guide
  # Extra details are not displayed in offense messages by default. Change
  # behavior by overriding ExtraDetails, or by giving the
--
--
Layout/ClassStructure:
  Description: 'Enforces a configured order of definitions within a class body.'
  StyleGuide: 'https://github.com/rubocop-hq/ruby-style-guide#consistent-classes'
  Enabled: false
  VersionAdded: '0.52'

[koic]

I see. Thanks!