[Fix #437] Fix a false positive for Performance/ChainArrayAllocation

[koic]

Fixes #437.

This PR fixes a false positive for Performance/ChainArrayAllocation when using select with block argument after select.

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[matthewhively]

Forgive my possible stupidity (I'm not terribly familiar with how the tests in rubocop work)
But wouldn't this still be wrong?
Wouldn't it flag select (QueryMethods#select) followed by a select (enumerable).
Which isn't a double select that requires optimization?

You would however want to flag the 3rd select here right?
model.select(:foo, :bar).select { |item| item.do_something }.select { |item| item.do_something_else }

[koic]

I'm not entirely sure, this patch works as follows:

it 'registers an offense' do
  expect_offense(<<~RUBY)
    model.select(:foo, :bar).select { |item| item.do_something }.select { |item| item.do_something_else }
                            ^^^^^^^ Use unchained `select` and `select!` (followed by `return array` if required) instead of chaining `select...select`.
                                                                ^^^^^^^ Use unchained `select` and `select!` (followed by `return array` if required) instead of chaining `select...select`.
  RUBY
end

So, this is a patch that distinguishes between select(:arg) and select { |x| x }. What potential issues might arise from this?

[matthewhively]

So, let me rephrase
with this code

expect_offense(<<~RUBY)
        model.select(:foo, :bar).select { |item| item.do_something }
                                ^^^^^^^ Use unchained `select` and `select!` (followed by `return array` if required) instead of chaining `select...select`.
RUBY

What should the suggested corrected code look like?

[koic]

Ah, I understand. This should definitely be recognized as a false positive and I've fixed it. Thank you!