[Fix #4656] Fix Style/ConditionalAssignment auto-correction

[akhramov]

Style/ConditionalAssignment cop's autocorrection results in invalid
syntax when it encounters assignment to unbracketed array.

This pull request modifies ConditionalAssignment cop's autocorrection so, it
wraps array in brackets, if needed.
This issue is very simillar to #3170, where Style/MutableConstant
wasn't able to properly handle assignment to unbracketed array.
Since both MutableConstant and ConditionalAssignment cops need to
check whether array node is bracketed or not, new method
Rubocop::AST::ArrayNode#bracketed? was introduced, to avoid
duplication.

---

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(rake spec) are passing.
• The new code doesn't generate RuboCop offenses that are checked by rake internal_investigation.
• 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).

[Drenmi]

I guess this happens because of interference from Lint/EndAlignment?

[akhramov]

Actually, Style/ConditionalAssignment realigns end keyword by itself. Please see #2719 / #2800 for details.

[bbatsov]

That looks extremely strange.

[akhramov]

@bbatsov

Agreed. Would it be better to have an "explanatory" variable? i.e.

indent = ' ' * 'bar = '.length
expect(new_source).to eq(<<-RUBY.strip_indent)
  bar = if foo
    1
  else
    [2, 5, 6]
  #{indent}end
RUBY

If so, I'd correct the other case, from which I've derived the style.

[Drenmi]

Is it possible to configure (from within the test suite) the auto-correct to produce a more ... reasonable style in the tests?

Either:

bar = if foo
        1
      else
        [2, 3]
      end

or:

bar = if foo
  1
else
  [2, 3]
end

[akhramov]

@Drenmi, thanks for guidance! Fixed.

[Drenmi]

Well done, @akhramov! Looks much better now. 🙂

[Drenmi]

Nice! Hadn't crossed my mind that parallel assignment is parsed as an array node. 🙂

[Drenmi]

With the fix to the test configuration, I'm good with this @bbatsov. 🙂